The continent was also thinning due to rifting, which could lead to isolation.
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Kelly Brunt, a scientist aboard the flight, is an expert in ice shelf rifting.
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Continental rifting requires the existence of extensional forces great enough to break the lithosphere.
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They've been rifting for a long time now, and the signs have been there for awhile.
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A timeline in action The East African Rift is unique in that it allows us to observe different stages of rifting along its length.
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As additional rifting in the south caused chunks of crustal material to sink, alien ocean brine was extruded upwards, oozing everywhere and smothering the surface in ice.
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Dramatic events, such as sudden motorway-splitting faults or large catastrophic earthquakes may give continental rifting a sense of urgency but, most of the time, it goes about splitting Africa without anybody even noticing.
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After months of reports about Antonio Brown's strained relationship with the Pittsburgh Steelers – which included sitting out Week 17, rifting with quarterback Ben Roethlisberger, and publicly requesting a trade – the saga finally came to an end.
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Although most of the time rifting is unnoticeable to us, the formation of new faults, fissures and cracks or renewed movement along old faults as the Nubian and Somali plates continue moving apart can result in earthquakes.
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"To be clear, the remaining floating glacial ice in the shelf does not appear to be showing signs of further rifting, but it is also the middle of the austral (southern hemisphere) winter, so we'll need to keep watch in subsequent warmer weather, possibly for many years," Christopher A. Shuman, a research scientist within the Cryospheric Sciences Laboratory at NASA Goddard Space Flight Center, told Motherboard in an email.
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Passive rifting, unlike active rifting, occurs principally by extensional tectonic forces as opposed to magmatic forces originating from convection cells or mantle plumes. Isostatic forces allow mantle material to rise under the thinning lithosphere. Subsidence and sedimentation occur during both the initial rifting stage and the post rifting stages. Only after initial rifting does any mantle melting occur.
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Active rifting was complete by 160 Ma. After this thermal subsidence occurred till the end of Cretaceous. During this time rifting separated North America from Africa forming a transform zone.
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Middle Paleocene to middle late Eocene tectonics of Northern Canada and Greenland Two rifting episodes created the Canadian Arctic Rift System. The first is referred to as the Boreal Rifting Episode which followed compression and exposure brought on by the Ellesmerian orogeny. The second is referred to as the Eurekan Rifting Episode and created most of the structures that comprise the Canadian Arctic Rift System. Both rifting episodes were active simultaneously from the Early Cretaceous to mid Tertiary.
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This was rifted in Toarcian times (Early Jurassic 190 Ma). Active rifting was complete by 160 Ma. After this thermal subsidence occurred till the end of Cretaceous. During this time rifting separated North America from Africa forming a transform zone . In the late Triassic and early Jurassic there were two stages of rifting involving extension and subsidence on the western margin of Iberia.
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Approximately 220 million years ago, during the late Triassic Period, the supercontinent Pangaea began to break apart. The focus of the rifting began somewhere between where present-day eastern North America and northwestern Africa were joined. As in all rifting environments, grabens formed. Many of these grabens were created, but for some of them extension stopped before full rifting occurred.
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Thermally-induced rifting in the Somali Basin and transform rifting along the Davie Fracture Zone began in the late Permian 225 million years ago, with Gondwana supercontinent beginning to break up in the Middle Jurassic (about 167 million years ago) when East Gondwana, comprising Antarctica, Madagascar, India, and Australia, began to separate from Africa; East Gondwana then began to separate about 115–120 million years ago when India began to move northward. The Seychelles Islands then underwent two more stages of rifting to isolate it from Madagascar and India. Between 84–95 million years ago rifting separated Seychelles/India from Madagascar. An initial period of transform rifting moved the Seychelles/India block northward.
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This rifting event caused the Atlantic Ocean to form. The other event was an active rifting event. This happened in the Lower Jurassic and caused the opening of the Indian Ocean. This breakup took 17 million years to complete.
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Rifting still continues today; primarily in the north, where active volcanoes are more plentiful.
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The transitional chemistry can be explained by back-arc rifting in the Bransfield Basin.
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Where only partial rifting occurred, basins formed. By definition, a basin is any area that collects sediments. These "aborted rifts" (rifts that are tectonically inactive and no longer collecting sediments) extend from Alabama to Newfoundland. Along certain basins, rifting was not partial.
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The trap series is dated to a time soon before the major rifting events began. Chorowicz (2005) illustrated the trap series surrounding the newer Neogene volcanics. This helps quantify the amount of crustal extension and gives a model of pre-rifting crustal connection.
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A collapsing coronae coupled with extensional stressing may result in rifting, creating a chasmata region.
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Atekwana also uses geophysics to investigate tectonic processes. Her geophysical studies reveal crust and upper mantle structures that inform the geodynamic processes associated with incipient rifting of continental crust. For example, Atekwana and colleagues show how geophysically imaged pre-existing basement structures in Malawi and Botswana influenced strain localization during early rifting. Another case study from the nascent Okavango rift in northwest Botswana provides evidence that pre-existing basement structures control rifting.
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The rifting in the valley is enlarging the lake, creating more wetlands in the surrounding area.
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The unconformity that separates the basement from the first sequences indicates the approximate time rifting began.
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Past rifting events have been recorded in the geologic record and major rifting events have been seen to have an aulacogen with two successful rifting arms. Some geologists have proposed that the East African Rift System will be the aulacogen in the future but as of present-day there seems to be no aulacogen and the rifting in the EARS does not show any evidence of slowing its motion. There is also the possibility to a subduction zone forming along the easternmost side of the continental Somali plate. This could be associated by the spreading of the Mid-Indian Oceanic ridge and the East African rift.
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Rifting in this area is still going on today. Such a long period of rifting leads to uplift due to prolonged lateral heat conduction in the mountain belt. This is backed by seismic evidence. Initial surface uplift began approximately 55 Ma during the Early Cenozoic era.
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Before the initial rifting began, Africa was one plate but as rifting proceeded the plate began to tear in three directions. The rifting propagated along three branches that have now formed three separate plates: the Arabian, Somali, and the Nubian (also mentioned as the African plate). In 1969, McKenzie and Morgan published a paper and systematically explained types of triple junctions and their stability. The Afar Triple Junction is known as a ridge-ridge-ridge or RRR triple junction.
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Successful rifting creates a spreading center like a mid-ocean ridge, which moves progressively further from coastlines as oceanic lithosphere is produced. Due to this initial phase of rifting, the crust in a passive margin is thinner than adjacent crust and subsides to create an accommodation space. Accumulation of non-marine sediment forms alluvial fans in the accommodation space. As rifting proceeds, listric fault systems form and further subsidence occurs, resulting in the creation of an ocean basin.
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This leads to a kind of orogeneses in extensional settings, which is referred as to rifting orogeny.
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The Mesozoic magmatic rocks are associated with Cimmerian and Laramide orogenic events that caused continental and oceanic rifting, followed by closures and collisions in vast areas of Iran (e.g., Sanandaj–Sirjan). The Mesozoic magmatic rocks can be divided into three groups: Volcanic rocks: These rocks occurred mainly as a result of extension or tension related to the continental rifting, or subduction of the developed oceanic lithosphere under the continental lithosphere (e.g., Central Alborz for continental rifting; Saghez-Sanandaj axis for subduction).
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Wells in the Pearl River Mouth basin have been studied to determine the subsidence history of the basin. Using backstripping methods, three separate rifting episodes were identified within the basin at 45-55 Ma, 45-25 Ma, and about 12-14 Ma with a fourth event at 5 Ma being identified in a single well. Most rifting in the basin was completed by 25 Ma, shortly after the time sea floor spreading began. Extension during rifting events was determined using McKenzie equations.
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The Kaltag acted as a transform fault with intermittent pulses of both extension and strike-slip displacement during three time intervals. Tectonism during the first time interval from Carboniferous to Permian was coeval with an early stage of the Boreal Rifting Episode. This was followed by a second time interval of tectonism from the latest Cretaceous to early Tertiary when the Boreal Rifting Episode was active and the Eurekan Rifting Episode was in an early stage of development. A third and final time interval of tectonism during the Miocene or Pliocene coincided with the final phase of the Eurekan Rifting Episode, during which time the Kaltag Fault was the northwestern boundary of the Queen Elizabeth Islands Subplate.
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This rifting created a divergent plate margin that would play an integral role of the future geologic processes to follow. Rifting, which involves the stretching of pre-existing crust and mantle lithosphere, was initiated by the existence of sufficient horizontal deviatoric tensional stress that broke the lithosphere. Eventually rifting gave way to sea floor spreading in the Atlantic and Gulf of Mexico in the mid Jurassic, around ≈165 Ma. Sea floor spreading is where new oceanic lithosphere is being created by upwelling of material, unlike rifting where it only involved the stretching of the crust. Convection currents in the sub-lithospheric mantle are the driving mechanisms that caused sea floor spreading to occur.
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Many rifts are the sites of at least minor magmatic activity, particularly in the early stages of rifting. Alkali basalts and bimodal volcanism are common products of rift-related magmatism. Recent studies indicate that post-collisional granites in collisional orogens are the product of rifting magmatism at converged plate margins.
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The Meso- and Cenozoic formation of the Atlantic rifting event show pre-, syn-, and post-rift tectono sedimentary units.
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The Eurekan Rifting Episode commenced in the Early Cretaceous as the Boreal Rifting Episode declined. Crustal stretching began at the south end of the rift system 130 million years ago, during which time supercontinent Laurasia was in the process of breaking apart. Rifting began from the Atlantic Ocean then propagated northwest where the Labrador Sea started opening in the Late Cretaceous. Seafloor spreading commenced in the southern Labrador Sea 75–60 million years ago, during which time Greenland moved north relative to mainland North America.
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From 1.4 to 1.2 Ga the Kibaran orogeny fused the Tanzanian and Congo cratons. From 1000 to 600 Ma the super-continent Gondwana was formed and the Pan-African orogeny sutured the Tanzanian and Kalahari cratons. The rifting of Gondwana occurred from 190 Ma to 47 Ma separating Madagascar from the eastern coast of Africa and placing the Seychelles/Mascarene Plateau northeast of Madagascar. The rifting of the Red Sea started around and the first rifting occurred in the northern East African Rift System around .
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The basin is understood to be a result of rifting within the Hatton–Rockall plateau. The age of the rifting is poorly constrained, but is thought to be of Cretaceous age. From wide-angle seismic profiles over the basin and the adjacent highs, a stretching factor of about 2 has been estimated.
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The third rifting arm runs south extending around through the countries of Kenya, Uganda, the Democratic Republic of Congo, Rwanda, Burundi, Tanzania, Zambia, Malawi and, finally, Mozambique. This southern rifting arm is better known as the East African Rift or the East African Rift System (EARS), when it includes the Afar Triangle.
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The transition between the continental and oceanic lithosphere that was originally created by rifting is known as a passive margin.
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The undersea trough through the strait is known as Bransfield Trough (). The basin is about 400 km long and 2 km deep, between the South Shetland Island Arc and the Antarctic Peninsula. It was formed by rifting behind the islands, which began about 4 million years ago. Ongoing rifting has caused recent earthquakes and volcanism.
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Volcanic passive margins (VPM) and non-volcanic passive margins are the two forms of transitional crust that lie beneath passive continental margins that occur on Earth as the result of the formation of ocean basins via continental rifting. Initiation of igneous processes associated with volcanic passive margins occurs before and/or during the rifting process depending on the cause of rifting. There are two accepted models for VPM formation: hotspots/mantle plumes and slab pull. Both result in large, quick lava flows over a relatively short period of geologic time (i.e.
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The Boreal Rifting Episode began in the Late Devonian and emanated southeastward from the Canada Basin into the North American continent. It caused uplift of the Pearya Geanticline and Sverdrup Rim, as well as crustal extension that led to thinning and subsidence of the regional lithosphere. The rifting extended only into the area that would be occupied by the future central Queen Elizabeth Islands and was aborted there due to interfering structural trends. In the extreme west, in the Banks Island area, extension of the Boreal Rifting Episode continued uninterrupted until the mid-Tertiary.
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Crustal uplift may have also provided stresses contributing to rifting. A slightly younger but possibly related geologic feature is the long Midcontinent Rift System adjacent to the southern end of the Mackenzie Large Igneous Province. The Lake Superior portion of the Midcontinent Rift System is bounded on the south by pre-existing continental faults that had substantial right-lateral movement before the formation of the Midcontinent Rift System. This period of rifting was a large event for copper mineralization, and the rifting event later deceased when the Grenville orogeny collision occurred.
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North of this, incipient rifting is magmatically manifested by unusual, shoshonitic lavas of the Hiyoshi complex, Fukutoku-oka-no-ba (or Sin Iwo Jima), and Iwo Jima . Rifting and spreading are inferred to be propagating northward at a rate of 10 to 40 cm/year , so the variations in tectonic and magmatic style seen along-strike north of 18°N provide an example of the sequence of events that occur at any one section across the back-arc basin as the rift evolves from updoming through rifting to true spreading.
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The Mesozoic saw the first stages of break-up of the supercontinent of Pangaea. Rifting began at the end of the Permian, with development of a series of rift basins over much of the British Isles. The rifts became more localised during the Jurassic and by the Cretaceous, most of the rifting has stopped, apart from the area south of the Variscan Front, where rifting continued into the Early Cretaceous. The Late Cretaceous saw the inundation of almost all parts of the British Isles by the "chalk sea".
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The difference in rifting and time gap between the northeastern and southwestern regions indicate the South China Sea is not a geologically homogeneous area, and its lithosphere could be divided into two areas, southwest and northeast according to its tectonic evolution. The reasons behind these differences in its rifting stage could be various, such as impact from different plates and different distribution of plumes under the crust. The Red River Fault along the western boundary of the South China Sea was believed to influence the rifting in the south and southwestern regions. Strike-slip faults.
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The overall chemistry and mineralogy of the Anahim magmas are analogous to regions of incipient continental rifting above a mantle plume.
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The rifting stopped before the land could become two separate continents. About 100 million years later, the last volcano went quiet.
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After the cessation of rifting, cooling causes the crust to further subside, and loading with sediment will cause further tectonic subsidence.
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Back-arc Rifting System in Middle Mesozoic In Middle-Jurassic, Hainan Island was in place at the back-arc rifting system. Until Early Cretaceous, the Paleo-pacific oceanic plate was then subducted under the South China Block in the northwest. As a result, the intrusive activities took place frequently as well. The granitoids produced in Jurassic, ca.
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Where only partial rifting occurred, basins formed, analogous to the present-day Basin and Range Province in the western United States. By definition, a basin is any area that collects sediments. These "aborted rifts" (rifts that are tectonically inactive and no longer collecting sediments) extend from North Carolina to Newfoundland. Along certain basins, rifting was not partial.
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This type of passive margin develops where rifting is oblique to the coastline, as is now occurring in the Gulf of California.
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In southern Norway the Permian was a period of W-E directed rifting with associated igneous activity, during which the Oslo graben formed.
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Newfoundland was re-exposed to the ocean in the Triassic when rifting began to form new oceanic crust and opened the Atlantic Ocean.
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This further confirms the presence of initiation of seafloor spreading along the spreading axis before the extinction of rifting in the Adare Basin.
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Furthermore, high heat flow is necessary to produce granulite facies metamorphic rocks in orogens, indicating extreme metamorphism at high thermal gradients. In-situ granitisation by the extreme metamorphism is possible if crustal rocks would be heated by the asthenospheric mantle in rifting orogens, where collision-thickened orogenic lithosphere is thinned at first and then underwent extensional tectonism for active rifting.
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Description of the oceanisation process through continental rifting Oceanisation is the process of formation of an ocean after continental rifting. The oceanisation is marked by the accretion of oceanic basalts between the drifting continental blocks and the incursion of marine waters and species in the rift basin.Abbate, Ernesto. Oceanisation processes and sedimentary evolution of the Northern Apennine ophiolite suite: a discussion. 1994.
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Rifting began along the whole of the Red Sea -Gulf of Suez rift system during the Late Oligocene. In the Gulf of Suez rift, the rifting culminated during the Burdigalian stage (late Early Miocene) (ca. 18 Ma). In the Middle Miocene break-up occurred along the whole length of the Red Sea rift with seafloor spreading beginning in the Late Miocene.
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These structures formed intermittently from late Proterozoic to early Tertiary time, with the latest period of reactivation having taken place during the Eurekan Rifting Episode.
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Rifting leading to the breakup of supercontinent Rodinia, which had formed in the mid- Stenian, occurred during this period, starting from 900 to 850 Mya.
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Formed between the Mesozoic and Cenozoic, Brazil has numerous offshore basins that contain oil, related to the rifting of the Atlantic Ocean. The Sergipe-Alagoas Basin is an example of Aptian age shale, conglomerate and sandstone deposited in the final phase of rifting, while the Miranga, Aracas, Dom Joao and Agua Grande fields reflect mid-Mesozoic lake-bed shales, with high oil-content Jurassic sandstones above them.
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Sections of the flood basalts have been eroded away, but still form a basaltic mountain range known as North Mountain. The rift valley eventually failed (see aulacogen) as the Mid-Atlantic Ridge continued to separate North America, Europe, and Africa. As in all rifting environments, grabens formed. Many of these grabens were created, but for some of them, extension stopped before full rifting occurred.
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The simplified geological evolutionary diagrams of basement evolution in the Junggar Basin region. 1. Rifting formed West Junggar Ocean (WJO) basin (in deep blue). 2. the termination of intra-plate oceanic magmatism, and subduction events formed the present Tangbale and Hongguleleng ophiolites (they represent the integration for the crust of West Junggar Ocean). 3. Maylia ocean basin (in pale blue) formed by rifting. 4.
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Rifting-to-spreading transition Passive continental margin A passive margin is the transition between oceanic and continental lithosphere that is not an active plate margin. A passive margin forms by sedimentation above an ancient rift, now marked by transitional lithosphere. Continental rifting creates new ocean basins. Eventually the continental rift forms a mid-ocean ridge and the locus of extension moves away from the continent-ocean boundary.
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In the Lau Basin east of the NFB the Pacific plate is subducting westward under Tonga trench in the highest rate of back-arc rifting known — where the Louisville seamount chain subducts under the Tonga trench rifting propagates at . This seamount chain–trench intersection propagates southward at a rate of and, as a consequence, Tonga Islands rotate clockwise at a rate of 9.3°/Ma.
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The basin includes five significant depocenters. The Inner Otway Basin, Torquay Sub-basin, Morum Sub- basin, Nelson Sub-basin, and Hunter Sub-basin formed as a result of two major, basin-wide rifting phases. At the onset of major north-south rifting in the late Jurassic several east-west trending extensional depocenters developed in the onshore part of the basin to define the Inner Otway Basin. Renewed rifting in the late Cretaceous was driven by a change in crustal extension style from north-south to northeast-southwest resulting in the structurally different, northwest-southeast trending Torquay, Morum, Nelson, and Hunter Sub-basins in the mid- and off-shore.
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The first phase of rifting ceased in the Albian at which time the basin underwent an erosive compressional period leading to the basin wide Otway unconformity.
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It is responsible for most of the major mountain systems outside the Antarctic Peninsula. Volcanism has been attributed to the rifting and also a mantle hotspot.
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Once rifting ceases, the mantle beneath the rift cools and this is accompanied by a broad area of post-rift subsidence. The amount of subsidence is directly related to the amount of thinning during the rifting phase calculated as the beta factor (initial crustal thickness divided by final crustal thickness), but is also affected by the degree to which the rift basin is filled at each stage, due to the greater density of sediments in contrast to water. The simple 'McKenzie model' of rifting, which considers the rifting stage to be instantaneous, provides a good first order estimate of the amount of crustal thinning from observations of the amount of post-rift subsidence. This has generally been replaced by the 'flexural cantilever model', which takes into account the geometry of the rift faults and the flexural isostasy of the upper part of the crust.
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This is consistent with a system that tends toward equilibrium: as matter rises in a mantle plume, other material is drawn down into the mantle, causing rifting.
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Rocks in this formation were seemingly formed in an arc environment and may be a result of rifting of basement rocks due to increased mantle plume activity.
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The modern Manihiki Plateau rifted from the Hikurangi Plateau, now located adjacent to New Zealand, in the Early Cretaceous. In the Early Cretaceous the Manihiki Plateau was much shallower, below sea level or less. Shortly after emplacement the initiation of the Tongareva triple junction resulted in extension, upwelling and rifting. Renewed rifting at about 116 Ma created the eastern margin, the Manihiki Scarp, and separated Manihiki and Hikurangi.
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The island province of Hainan is located off the South coast of China's mainland. It was separated from the mainland by tectonic rifting and coastal erosion. The parts of the South China Sea that China claims, formed by the evolution of continental rifting into oceanic spreading during the mid Cenozoic. There are numerous sea mounts and island carbonate reefs that have developed on horsts formed during the extension.
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Two different models on how the extension initiated have been proposed, by Wang (2009) and by Cullen (2010). Wang's model for South China Sea rifting proposes a different area of rift development. The north and northeastern parts of the South China Sea formed their rifts earlier in the Paleocene. The south and southwestern parts of the South China Sea showed a later rifting around the Eocene or later.
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The faulted crust transitions into oceanic crust and may be deeply buried due to thermal subsidence and the mass of sediment that collects above it. The lithosphere beneath passive margins is known as transitional lithosphere. The lithosphere thins seaward as it transitions seaward to oceanic crust. Different kinds of transitional crust form, depending on how fast rifting occurs and how hot the underlying mantle was at the time of rifting.
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India, Memoir 31, pp. 259–278. At that time, the Bundelkhand- Aravalli-BGC and the Marwar craton lie on the eastern side and western side respectively as the rifting phase separated the Bhilwara Gneissic Complex (BGC) from the Marwar craton. The oceanic basin created in the course of rifting received the Delhi Supergroup sediments. The compressional phase that followed led to eastward subduction of the western Marwar craton.
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In the 36 million years since their formation, rifting may have subsequently separated them by as much as 25–90 km, depending on their original locations during eruption.
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These sediments formed within rifting basins and contain both volcanic and carbonate rocks. The Negra Muerta caldera may host a porphyry copper deposit, which is however not mined.
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The East European Craton has a very complex tectonic history with extensive Proterozoic and Paleozoic rifting, a large portion of which is of early deep mantle plume origin.
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Attempts to reconstruct the craton's tectonic history have focused extensively on the east–west asymmetry. The presence of a collisional suture suggests the CSBC collided with an island arc terrane along a boundary directed north–south before 2.69 Ga. Alternatively, the Eastern Slave may be an attenuated and modified Mesoarchaean lithosphere which developed during rifting at 2.85–2.70 Ga. The mantle lithosphere under the western Slave can be 400 Ma older than that underlying the eastern Slave. Furthermore, rifting is backed up by the existence of younger arc or back-arc rocks that overly the CSBC, but make up most of the Eastern Slave. However, whether the Eastern Slave was the result of rifting or the accretion of another terrane is still up for debate. Following the 2.7 Ga rifting or accretion event, the Slave underwent large scale extension at 2680 Ma resulting in the formation of the > 400x800 km Burwash Basin, widespread mafic sills, and other younger turbidites along the northwestern margin.
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The opening of the South Atlantic Ocean divided West Gondwana (South America and Africa), but there is a considerable debate over the exact timing of this break-up. Rifting propagated from south to north along Triassic–Early Jurassic lineaments, but intra-continental rifts also began to develop within both continents in Jurassic–Cretaceous sedimentary basins; subdividing each continent into three sub-plates. Rifting began at Falkland latitudes, forcing Patagonia to move relative to the still static remainder of South America and Africa, and this westward movement lasted until the Early Cretaceous . From there rifting propagated northward during the Late Jurassic or Early Cretaceous most likely forcing dextral movements between sub-plates on either side.
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This break-up was associated with a gradual reduction in the rate of rifting along the Gulf of Suez with most activity stopping by the beginning of the Pliocene.
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The initial rifting of Pangea began 260 million years before present during the Late Permian and persisted through the Triassic. Throughout this stage of rifting, the continental crust was thinned and separation of North America from northwestern Africa began. Normal faulting in a northeast-southwest direction created a series of grabens and half-grabens developed as the thinned crust subsided. Subsidence led to the formation of a shallow basin without forming an ocean.
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Animation of the rifting of Pangaea There have been three major phases in the break-up of Pangaea. The first phase began in the Early-Middle Jurassic (about 175 Ma), when Pangaea began to rift from the Tethys Ocean in the east to the Pacific in the west. The rifting that took place between North America and Africa produced multiple failed rifts. One rift resulted in a new ocean, the North Atlantic Ocean.
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The Niger Delta Basin was formed by a failed rift junction during the separation of the South American plate and the African plate, as the South Atlantic began to open. Rifting in this basin started in the late Jurassic and ended in the mid Cretaceous. As rifting continued, several faults formed many of them thrust faults. Also at this time syn-rift sands and then shales were deposited in the late Cretaceous.
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The most important events in the geolocical evolution of the North Sea are outlined as: # Precambrian events - formation of Highlands and basement elements. # The Caledonian plate cycle - Late Cambrian to Late Silurian Athollian and Caledonian Orogenies. # The Variscan plate cycle - Devono-Carboniferous rifting, Variscan Orogency, and creation of the Pangaea supercontinent. # Permo-Triassic rifting and thermal subsidence - Late Permian subsidence of the Moray Firth and east-west trending of the Permian Basin.
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On the Toarcian-Aalenian transgression, the High Atlas domain experienced a long process of extension and rifting, recorded by the presence of marine carbonates and shales, found on the Wazzant Formation Beds. It is related to the formation of the Atlantic Rifting to the west and of the formation of the Tethys Ocean to the north.El Harfi, A., Guiraud, M., & Lang, J. (2006). Deep- rooted “thick-skinned” model for the High Atlas Mountains (Morocco).
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Rifting that opened the South China Sea around 40 Ma may be connected with some dolerite intrusions. The Penglai Orogeny started about 10 Ma and continues at the present time.
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The main basin is considered to be an intramontane basin resulting from crustal rifting associated with post- Caledonian extension, possibly accompanied by strike-slip faulting along the Great Glen Fault system.
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The arc crust is under extension or rifting as a result of the sinking of the subducting slab. Back-arc basins were initially a surprising result for plate tectonics theorists, who expected convergent boundaries to be zones of compression, rather than major extension. However, they are now recognized as consistent with this model in explaining how the interior of Earth loses heat. Cross- section sketch showing the development of a back-arc basin by rifting the arc longitudinally.
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Weight causes crustal flexure and subsidence Lithospheric stretching/thinning during rifting results in regional necking of the lithosphere (the elevation of the upper surface decreases while the lower boundary rises). The underlying asthenosphere passively rises to replace the thinned mantle lithosphere. Subsequently, after the rifting/stretching period ends, this shallow asthenosphere gradually cools back into mantle lithosphere over a period of many tens of millions of years. Because mantle lithosphere is denser than asthenospheric mantle, this cooling causes subsidence.
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The Phoenix Plate is now considered part of the larger Antarctic Plate due to a lack of relative movement between the two since spreading ceased. However, subduction in the South Shetland Trench did not cease. Slab rollback of the former Phoenix Plate underneath the South Shetland Islands caused rifting to develop in the Antarctic Peninsula creating the Shetland Plate and the Bransfield Basin. Rifting centers in the Bransfield Basin continue to separate the Shetland Plate from the Antarctic Peninsula.
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In the Late Devonian rifting and magmatic activity occurred within the platform leading to the formation of the Dnieper-Donets Rift. This event was possibly caused by a cluster of mantle plumes.
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In the Neoproterozoic, the four kilometre thick Mackenzie Mountains Supergroup deposited in a poorly understood basin. Hydrothermal fluids emplaced base metals into these deposits, likely during rifting that lasted into the Paleozoic.
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It is part of the Indian Shield that was formed from a series of cratonic collisions.Mishra, D.C.; Kumar, M. Ravi. Proterozoic orogenic belts and rifting of Indian cratons: Geophysical constraints. Geoscience Frontiers.
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The geology of Brazil includes very ancient craton basement rock from the Precambrian overlain by sedimentary rocks and intruded by igneous activity, as well as impacted by the rifting of the Atlantic Ocean.
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After the deposition a period of uplift and erosion occurred due to the further expansion and rifting of the Atlantic Ocean that forms an unconformity at the top if the middle Kimmeridgian deposits.
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Thermal subsidence and Arabian plate stretching (that resulted from the fragmentation of Gondwana in the Late Permian) resulted in extensional faulting and the early rifting of Zagros that opened the Neo-Tethys Sea.
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Zhang, Q. S. (1988). Early crust and mineral deposits of Liaodong peninsula, China. Beijing: Geol. publ. house. The rocks of similar age on both sides of the Belt support the idea of rifting.
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The first period of rifting identified in the area was during the Devonian as part of the development of the Orcadian Basin. Rocks of this age are known from parts of the Rona Ridge and the Corona Ridge. Rifting appears to have continued into the Carboniferous with rocks of this age also locally preserved above the Devonian. During the Permian to Triassic periods thick sequences of continental deposits were formed in a series of basins, such as the Papa Basin.
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After a 6.5 Ma hiatus, rifting renewed and rift-related subsidence began in the Turonian. This rifting phase is marked by a change in crustal extension direction from north-south to northeast-southwest resulting in the deposition of large and deep depocenters in the mid- and off-shore basin. Syn-rift deposition includes ~1300 meters of fluvial and deltaic sediments that comprise the Shipwreck Group. A major marine transgression in the Campanian produced ~5000 meters of deltaic and marine Sherbrook Group sediments.
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These were deposited during periods of lava fountain activity. The vent area contains volcanic bombs up to long and small deposits of sulfur precipitated from volcanic gases. Like other Iskut-Unuk River Cones, The Volcano has its origins in continental rifting—a long rupture in the Earth's crust where the lithosphere is being pulled apart. This incipient rifting has formed as a result of the Pacific Plate sliding northward along the Queen Charlotte Fault, on its way to the Aleutian Trench.
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Situated on Bathurst Island is the Southeast Bathurst Fault Zone, a north-south trending system of normal faults that form a graben-like structure. It originally formed during the Boreal Rifting Episode, but was reactivated during a period of regional uplift and compression brought on by the Eurekan Rifting Episode. The South Cape Fault Zone to the northeast is a major east-west trending fault extending throughout much of the length of Jones Sound. It cuts across the peninsulas of southern Ellesmere Island.
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Rifting resumed beginning in the Oligocene, and is commonly held to have increased since the middle Pliocene, causing the formation of basins in the form of grabens. The new rift structure may follow the Precambrian and Paleozoic faults, such as when the dormant Primorsky fault, of the Central Basin, began to extend again in the late Cenozoic. Magmatic activity and rifting may also be independent events. Outside of the grabens basalt volcanics erupted from either end of the rift system during the uplift.
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The Variscan orogeny is the oldest event for which there is evidence in Dorset, forming a major series of thrust faults in Carboniferous and older rocks. These thrusts trend west–east, dip moderately towards the south and have controlled later basin development and subsequent phases of inversion. During the Permo-Triassic the area was affected by a phase of rifting that reactivated the older thrusts in extension. These extensional faults were themselves reactivated during further rifting in Jurassic to early Cretaceous times.
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South of the Walvis Ridge and Rio Grande Rise the Paraná and Etendeka magmatics resulted in further ocean-floor spreading and the development of rifts systems on both continents, including the Central African Rift System and the Central African Shear Zone which lasted until . At Brazilian latitudes spreading is more difficult to assess because of the lack of palaeo-magnetic data, but rifting occurred in Nigeria at the Benue Trough . North of the Equator the rifting began after and continued until .
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In the initial stage of the development of South China Sea, a basin was developed by extension to form two passive margins. The consensus is that the extension propagated from the northeast to the southwest, although some experts argue that the southwest basin is in fact older. The rifting and multiple grabens initiated around 55 Ma, based on seismic profiles across the southern China Shelf. The rifting intensified around 50 Ma due to the collision of the Indian and Eurasian plates.
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Prior to rifting, enormous continental flood basalts erupted on the surface and uplift of the Ethiopian, Somali, and East African plateaus occurred. The first stage of rifting of the EAR is characterized by rift localization and magmatism along the entire rift zone. Periods of extension alternated with times of relative inactivity. There was also the reactivation of a pre-Cambrian weakness in the crust, a suture zone of multiple cratons, displacement along large boundary faults, and the development of deep asymmetric basins.
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Matachewan Dike Swarms Swarms of mafic dikes and sills are typical of continental rifting and can be used to time supercontinent breakup. Intrusion of the 2,475- to 2,445-million-year-old Matachewan-Hearst Mafic Dike Swarm and the 2,490- to 2,475-million-year-old East Bull Lake suite of layered mafic intrusive rocks are interpreted as indicating early Paleoproterozoic, mantle-hotspot driven rifting centered near Sudbury, Ontario, during the onset of Kenorland breakup. Radiometric dating shows that the Wyoming province's Blue Draw Metagabbro was undergoing rifting at , the same time the emplacement of the long belt of mafic layered intrusions in the Sudbury region. In the northern Black Hills of southwest South Dakota the 2,600- to 2,560-million-year-old Precambrian cystalline core, the Blue Draw Metagabbro, is a thick layered sill.
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The traps evolved along the then eastern continental margin of India, following rifting of Gondwanaland. Over the epochs, the upper part of the lava deformed in a cold, brittle fashion and formed graben structures.
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There are several models for forming NVPM. Passive rifting can follow McKenzie's pure shear model, Wernicke's simple shear model, or a composite model combining features of both, as observed at the Galicia bank NVPM.
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The rifting took place in the Paleoproterozoic around 1864 Ma, and was followed by E W orientated compressional deformation ca. 1850 Ma with the development of northerly trending isoclinal folds and associated faults.
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The TGB, at 2.7 billion years old, dates back to the formation of the supercontinent Kenorland between 2.8 and 2.6 billion years ago. This large landmass consisted of the Baltic and Siberian shields of Eurasia and Archean provinces of North America, including the Superior craton of which the Temagami belt occupies a part. Rifting of Kenorland began 2.45 billion years ago in Ontario with the formation of several large igneous provinces. Initial rifting is represented by basal mafic volcanic rocks in the nearby Huronian Supergroup.
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During the Early Mesozoic, the supercontinent Pangea just finished its assembly and almost immediately started breaking apart. The rifting began to take place during Early to Middle Jurassic (201–163 million years ago), and gradually formed two extensive landmasses – Laurasia and Gondwana. The continents then continued to be ripped apart into smaller land that resembled modern continents throughout late Mesozoic and Cenozoic. The breakup of continents did not happen uniformly, and modern continents were formed at different speeds while experiencing repeated collision and rifting.
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The Jurassic is probably the most important geological time for hydrocarbon exploration in the North Sea. Many accumulations are in Jurassic reservoir, the Kimmeridge clay is considered the most important source rock and structures formed during rifting form excellent traps. In the first place rifting was responsible for the deposition of organic rich source rock due to anoxic conditions in the deep isolated rift basins. Possibly the most important phase to create structures and traps for the natural resources we try to collect today.
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Rifting, the slow pulling apart of a tectonic plate, has produced the East Africa Rift system and its many basins and lakes. The system, on the boundary between the African Plate (Nubian Plate) and the Somali Plate, has two branches, both oriented north- south. Rifting in the western branch, called the Albertine Rift, began between 25 and 10 million years ago. The Ruzizi River lies along the western rift, which includes, from north to south, lakes Albert, George, Edward, Kivu, Tanganyika, Rukwa, Malawi, and others.
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Most examples come from areas of active continental rifting such as the Basin and Range Province. Bimodal volcanism has also been described from areas of transtension,Till, A.B., Roeske, S.M., Bradley, D.C., Friedman, R. & Layer, P.W. 2007. Early Tertiary transtension-related deformation and magmatism along the Tintina fault system, Alaska, The Geological Society of America Special Paper 434, 233–264 the early phases of back-arc basin formationFujioka, K., Nishimura, A., Koyama, M., and Kotake, N., 1990. Bimodal arc volcanism and backarc rifting along Izu-Bonin Arc.
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During the Triassic-Early Jurassic, 252 to 200 Ma, there was a phase of new north to south rifting events due to the break up of the super-continent Pangea caused W-E extension across the Northern German Basin. These extensions in the crust created the Triassic grabens such as the local the Gluckstadt Graben, while also initiating the salt tectonics seen in the region. This rifting event was then followed by another phase of subsidence due to sedimentary loading and lithospheric thermal relaxation.
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In the Late Jurassic, the third rifting event took place in response to the North Sea doming event. Major extensional faulting and rifting began approximately 157-155 Ma allowing for the Zechstein evaporites to form a detachment between basement rocks and upper stratigraphy largely influencing the natural gas and oil formation seen across the North German Basin. Organic-rich mudstones from the Kimmeridge Clay Formation is the source of the majority of the North German Basin's hydrocarbons which was restricted from migrating upward by the Zechstein salt.
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Rifting began in the early Mesozoic, in the North Dobogrea-South Crimea Aulacogen, likely related to the strike-slip movement of the Tornquist-Teysseire Lineament. Ocean rifting through the Triassic separated Europe from the Preapulian Block. As the spreading of the Tethys Ocean continued, the Moesian Platform was rotated to the northwest and North Dobogrea experienced compression. The crust began to shorten and compress in the area of the Carpathian Mountains, as the Transylvanian nappe formations were obducted onto the edge of the continent.
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In Late Triassic and Early Jurassic there were two stages of rifting involving extension and subsistence on the western margin of Iberia. It also extended the western margin. The Iberian Abyssal Plain, off the west coast of Portugal and Spain, formed 126 Ma. This separated Newfoundland's Grand Banks, with Galica Bank and Flemish Cap being split at 118 Ma. By Early Cretaceous, 110 Ma rifting occurs on west and north west edges. In the Mesozoic, Late Jurassic Africa started moving east, and the Alpine Tethys opened.
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Production of REE around the world A rare-earth element-iron-lead-zinc (REE-Fe-Pb-Zn) system was formed from extensional rifting with upwelling of mantle, and therefore magma fractionation. There were multiple rifting events resulting in the deposition of iron minerals and the occurrence rare earth element was closely related to the iron and carbonatite dykes. The REE-Fe-Pb-Zn system occurs in an alternating volcanic and sedimentary succession. Apart from REE, LREE (light rare earth elements) are also found in carbonatite dykes.
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From the Permian until the Early Jurassic, the Comoros region experienced Karoo rifting, on a northeast–southwest trend. During the Middle Jurassic and Early Cretaceous, an ocean basin, running north–south, formed along the Davie Ridge.
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From the Permian until the Early Jurassic, the Comoros region experienced Karoo rifting, on an northeast–southwest trend. During the Middle Jurassic and Early Cretaceous, an ocean basin, running north–south, formed along the Davie Ridge.
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The Passaic is mostly shallow lakes, playa, and alluvial fan deposits resulting from the rifting of Pangea. The red color is often evidence that the sediments were deposited in arid conditions.Faill, R.T., (2004). The Birdsboro Basin.
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Three units compose the Pinguicula Group, deep water shales, mid depth carbonates and intertidal carbonates, suggesting an ocean basin environment. Formation of the Pinguicula basin is thought to be related to Laurentia rifting from another unknown continent.
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Is It My Turn is based on the poem Spellbinding by Deborah Schnitzer, who in turn was inspired by Gertrude Stein. Schnitzer has collaborated with Shelagh Carter several times on her films, starting with Rifting/Blue (2005).
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The tectonic setting was one of a rifting continental margin. New continental crust would have resulted in chemical weathering. This weathering would pull CO2 out of the atmosphere, cooling the planet through the reduction in greenhouse effect.
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Rifting during the Paleogene led to the formation of rift basins in which thick sequences of clastic rocks were deposited that are exposed at the eastern end of the island in the John Crow and Wagwater belts.
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It is a reference to the theory that the New Madrid quake was the result of a failed "rifting" of North America, but also to the deep racial and social divides that are portrayed throughout the story.
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Basin formation was initiated in the middle Eocene as extension related to the opening of the Makassar straits and Celebes Sea rifted the crust of Eastern Borneo. This rifting created a broad system of half grabens that reverse polarity along NNE-SSW and N-S trending normal faults. Thermal subsidence in the late Eocene and early Oligocene induced minor reactivation along the existing faults. During the late Oligocene there was a brief renewal of extension and rifting along the northern margin of the basin, while the other basin margins experienced uplift.
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The main period of rifting started during the Middle Jurassic, continuing into the Late Jurassic and possibly later. It was at this time that the Faroe-Shetland Basin took in its current shape. There was a further episode of rifting during the Late Cretaceous to Paleocene that locally modified the existing basins and formed new depocentres such as the Foinaven Sub-basin. At the end of the Paleocene, the area was affected by magmatism, part of the North Atlantic Igneous Province and a short-lived phase of uplift.
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Deposition of the Pinguicla group began at 1.38 Ga after a significant period of weathering. Deposition of these sediments indicates a period of rifting and extension in the area, as supported by the incidence of the Hart River volcanic at the same time period. The period of rifting and crustal extension embodied by the Hart River volcanics was followed by basin sedimentation represented by the Pinguicula group. The Pinguicula group is separated from the Wernecke Supergroup by an angular unconformity, representing an erosional stage after the Racklan orogenic event.
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The NW trending rift basin originated when the basement rocks were extended between the Triassic and early Cretaceous periods through forces related to the rifting of Gondwana. As the Blue Nile basin formed, it was filled with clastic and marine sediments. In the late Miocene further rifting occurred in a NW-SE extension associated with the Main Ethiopian rift, which formed NE-trending faults. In the Quaternary (2.5 Ma - present) the region was subject to further stresses as the Main Ethiopian rift opened obliquely, creating N, ESE and NW trending extensions within the basin.
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The Southeast Bathurst Fault Zone is a north-south trending system of extensional faults forming a graben-like structure on southeastern Bathurst Island in the Canadian Arctic Archipelago. It lies within the Boothia Uplift and is one of several fault zones associated with the Canadian Arctic Rift System. The fault zone formed in the latest Cretaceous to early Tertiary when extension of the Boreal Rifting Episode penetrated the North American continent from the Canada Basin. The Southeast Bathurst Fault Zone was reactivated when the Eurekan Rifting Episode uplifted and compressed the region during the Eocene.
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The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems. Major rifts occur along the central axis of most mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates. Failed rifts are the result of continental rifting that failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a triple junction where three converging rifts meet over a hotspot.
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Orogenic cycle of rifting, subduction, and accretion During the Jurassic period, Pangea began to pull apart causing separation of North America from South America. This rifting produced a subduction zone where the Nazca Plate was subducting to the east under the South American Plate. Part of this subducting plate was the Baudo- Island Arc separated from the South American continent by the marginal Colombian Sea. The formation of the extensional back-arc basin associated with this subduction is the origin of the Middle Magdalena Basin in the late Jurassic.
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During the Middle-Late Jurassic, the center of the North Sea underwent a doming acknowledged by the Middle Jurassic erosional unconformity, the erosion of > of Upper Triassic and Lower Jurassic strata. The dome raised above sea level during the Middle Jurassic and began to deflate due to rifting in the Late Jurassic. Though the mechanism forming the North Sea Rift Dome is not particularly well understood, the development of the dome seems to be consistent with an active rift model having a broad-based ( diameter) plume head influencing the Late Jurassic rifting.
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At 84 million years ago oceanic crust started to form in the Mascarene Basin, causing a rotation of the Seychelles/India land mass. This continued until 66 million years ago when new rifting severed the Seychelles from India forming the currently active Carlsberg Ridge. The rift jump coincided with the maximum output of the Deccan Traps, and volcanics found on the Seychelles Plateau have also been linked with this event. This has led to suggestions that the initiation of the Reunion plume caused rifting to jump to its current location.
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This gave the volcano its massive profile and consequently Maitland might have had a broad lava plateau like other large NCVP shields. Like other Northern Cordilleran volcanoes, Maitland Volcano had its origins in continental rifting—a long rupture in the Earth's crust where the lithosphere is being pulled apart. This incipient rifting formed as a result of the Pacific Plate sliding northward along the Queen Charlotte Fault, on its way to the Aleutian Trench. As the continental crust stretched, the near surface rocks fractured along steeply dipping cracks parallel to the rift known as faults.
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The mountain-building and rifting events left areas of high relief above the low basin of the Midcontinent rift. Over the next 1,100 million years, the uplands were worn down and the rift filled with sediments, forming rock ranging in thickness from several hundred meters near Lake Superior to thousands of meters further south.Ojakangas and Matsch, Minnesota’s Geology, pp. 57–59. While the crustal tectonic plates continued their slow drift over the surface of the planet, meeting and separating in the successive collision and rifting of continents, the North American craton remained stable.
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Tectonic activity along the North Coast of British Columbia and Southeast Alaska is characterized by transform movements of the Queen Charlotte Fault, a plate boundary where the Pacific Plate skids by the North American Plate. As the Pacific Plate moves northward to the Aleutian subduction zone, it generates rifting in the North American continent. Magma rises along cracks created by the rifting, and eventually erupts on the surface to form a volcano. This geological process has, over time, created the Northern Cordilleran Volcanic Province, which is the most volcanically active area in Canada.
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The origin of Chauncey Peak and the Metacomet Ridge dates back 200 million years ago with the rifting apart of North America from Eurasia in the process that would ultimately create the Atlantic Ocean. In the area that is now the Metacomet Ridge and surrounding sedimentary rock basin, massive basalt (traprock) lava flows spread across the prehistoric rift valley, some of them several hundred feet thick, over a period of 20 million years. Sediment accumulated between lava flows and lithified into sedimentary rock. After the rifting processes ceased, layers of strata faulted and tilted upward.
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The tectonic evolution of the Transantarctic Mountains appears to have begun when Antarctica broke away from Australia during the late Cretaceous and is ongoing, creating along the way some of the longest mountain ranges (at 3500 kilometers) formed by rift flank uplift and associated continental rifting. The Transantarctic Mountains (TAM) separate East and West Antarctica. The rift system that formed them is caused by a reactivation of crust along the East Antarctic Craton. This rifting or seafloor spreading causes plate movement that results in a nearby convergent boundary which then forms the mountain range.
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The origin of Totoket Mountain and the Metacomet Ridge dates back 200 million years ago with the rifting apart of North America from Eurasia in the process that would ultimately create the Atlantic Ocean. In the area that is now the Metacomet Ridge and surrounding sedimentary rock basin, massive basalt (traprock) lava flows spread across the prehistoric rift valley, some of them several hundred feet thick, over a period of 20 million years. Sediment accumulated between lava flows and lithified into sedimentary rock. After the rifting processes ceased, layers of strata faulted and tilted upward.
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A fourth way to classify passive margins is according to the nature of sedimentation of the mature passive margin. Sedimentation continues throughout the life of a passive margin. Sedimentation changes rapidly and progressively during the initial stages of passive margin formation because rifting begins on land, becoming marine as the rift opens and a true passive margin is established. Consequently, the sedimentation history of a passive margin begins with fluvial, lacustrine, or other subaerial deposits, evolving with time depending on how the rifting occurred and how, when, and by what type of sediment it varies.
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Tectonic and magmatic features associated with the Mackenzie Large Igneous Province, including the rifting that created the Poseidon Ocean. Red star shows the initial Mackenzie plume zone relative to the lithosphere. The Poseidon Ocean was an ocean that existed during the Mesoproterozoic period (from 1.6 to 1.0 billion years ago) of the geologic timescale. It began to form when a hotspot collided with lithosphere that was already in an extensional regime that allowed rifting to occur at the onset of hotspot volcanism that created the Mackenzie Large Igneous Province.
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The quantitative approach was further developed by many scientists later. As the field of geodynamic study expanded, analogue modelling increased, especially for large- scale geological processes. Examples include proto-subduction subduction in plate tectonics, collision, diapirism, and rifting.
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The Matachewan hotspot was a volcanic hotspot responsible for the creation of the large 2,500 to 2,450 million year old Matachewan dike swarm, as well as continental rifting of the Superior and Hearne cratons during the Paleoproterozoic period.
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As Africa subducts beneath the Aegean Sea Plate the slab essentially pulls the over-riding plate with it, inducing extension. Rifting occurs as the plate stretches weakening the thickened crust causing its collapse upon itself, creating the basin.
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The rifting in the Black Sea also increased heat flow into the Zonguldak basin during the Cretaceous. Heat flows were as high as 1.5–1.75 HFU, and the temperature of the sediment water interface was about 25 °C.
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This model illustrates that in Carboniferous, due to possible rifting, the Lesser and Greater Himalaya were separated by a north-dipping normal fault. In this reconstruction, the former is the footwall and the latter is the hanging wall.
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The bedrock geology of New England was heavily influenced by various tectonic events that have occurred since the Paleozoic Era including the accretion of land masses that formed various continental terranes to the Mesozoic rifting of the Hartford Basin.
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The sediment accumulated during the rifting of Pangea in the Triassic age. Also, a basaltic igneous rock called diabase formed dykes and sills later in the Jurassic as the Atlantic Ocean began to form.Faill, R.T. (2004). The Birdsboro Basin.
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The Lake's geology is represented by the Bara-lacha-la Pass, which is reported to be an early rifting event on the northern Indian passive margin and that the Basalts which are emplaced along the trans- tensional faults indicate that.
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Coastal sedimentary basins formed as a result of the rifting apart of the supercontinent Pangaea, opening the Atlantic Ocean and now hold Ivory Coast's offshore oil and gas reserves. Clastic sediments formed throughout the Neogene and up to recent times.
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Some rifts show a complex and prolonged history of rifting, with several distinct phases. The North Sea rift shows evidence of several separate rift phases from the Permian through to the Earliest Cretaceous, a period of over 100 million years.
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The Moinian rocks of Ross-shire and Sutherland are intruded by a distinctive set of granitic sheets, which give latest Proterozoic intrusion ages in the range 611-588 Ma. It has been suggested that these granites formed associated with rifting.
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The lack of erosion and deformation processes record the history and development of Venus.Basilevsky, Alexander T., and James W. Head. "Beta Regio, Venus; Evidence For Uplift, Rifting, And Volcanism Due To A Mantle Plume." Icarus 192.1 (2007): 167-186. GeoRef. Web.
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This hotspot, known as the Mackenzie hotspot, produced passive rifting to form a triple junction. As two of the rift arms continued to grow, they created the Poseidon Ocean basin. The third rift arm failed to open fully, creating an aulacogen.
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Towards the south the two lines converge and give place to one great valley (occupied by Lake Nyasa, or Lake Malawi), the southern part of which is less distinct due to rifting and subsidence than the rest of the system.
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Topographic map of Zealandia, showing Bollons Seamount in the southweast Bollons Seamount or Bollons Tablemount is a seamount just east of the international date line, a few hundred miles off the coast of New Zealand. It represents a continental fragment that separated from Zealandia as a result of rifting. The seamount was involved in a 2002 survey and collection project defined to find the edge of New Zealand's continental shelf. The Bollons Seamount has been shown to be a site of extensive Cretaceous-era rifting in the area towards the southern Chatham Rise between 83.7 and 78.5 MYA.
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From eight to four million years ago, volcanism rates were higher than they are at present. Magma production during this volcanic phase was most active from seven to five million years ago and was related to a period of rifting along the Pacific and North American Plate boundary. Between four and three million years ago in the Pliocene epoch, a pause in volcanic activity began to happen. The most recent magmatic phase ranging from two million years ago to present resulted from nearby areas of rifting during a period of compression between the Pacific and North American plates.
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The Bylot Supergroup in Baffin Island and Bylot Island is six kilometers thick with a combination of undeformed volcanic, clastic and carbonate rocks deposited during a phase of renewed rifting. The Borden Peninsula is divided into horst and graben structures by normal faults from local rifting and subsidence 1.27 billion years ago. The Nanisivik Mine extracts zinc and lead from these carbonates. The Bylot Supergroup is known as the Fury Group and Hecla Group along the Fury and Hecla Strait, where it overlies Archean and Paleoproterozoic rocks with nearly six kilometers of material, likely deposited over the span of 75 million years.
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As the ocean plate splits, the ridge forms at the spreading center, the ocean basin expands, and finally, the plate area increases causing many small volcanoes and/or shallow earthquakes. At zones of continent-to-continent rifting, divergent boundaries may cause new ocean basin to form as the continent splits, spreads, the central rift collapses, and ocean fills the basin. Active zones of mid-ocean ridges (e.g., the Mid- Atlantic Ridge and East Pacific Rise), and continent-to-continent rifting (such as Africa's East African Rift and Valley and the Red Sea), are examples of divergent boundaries.
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Associated offshore basaltic flows reach as far south as the Falkland Islands and South Africa. Traces of magmatism in both offshore and onshore basins in the central and southern segments have been dated to 147–49 Ma with two peaks between 143 and 121 Ma and 90–60 Ma. In the Falkland segment rifting began with dextral movements between the Patagonia and Colorado sub-plates between the Early Jurassic (190 Ma) and the Early Cretaceous (126.7 Ma). Around 150 Ma sea-floor spreading propagated northward into the southern segment. No later than 130 Ma rifting had reached the Walvis Ridge–Rio Grande Rise.
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A. Clifford (1986) p.336 The area's structural weakness is exemplified by alternating periods of uplift and subsidence originating in the Late Precambrian, commencing with the Pan-African orogeny that consolidated a number of proto-continental fragments into an early Gondwanaland. Rifting commenced in the Early Cretaceous, peaked in the Late Cretaceous, and ended in the early Cenozoic, resulting in the triple junction within the basin. The Late Cretaceous rifting event is characterized by formation of a sequence of northwest-trending horsts and grabens that step progressively downward to the east; the Sirte Trough represents the deepest portion of the basin.
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Paleogeographic reconstruction of WARS and TAM Breakup of the super-continent Gondwana started in the early Jurassic around 184 million years ago (Ma), but Antarctica did not break up from Australia until the late Cretaceous (80 Ma). Just before the breakaway in the Late Jurassic and Early Cretaceous, rifting began to occur near the soon- to-be Transantarctic Mountains. It is uncertain whether this first episode of rifting caused any uplift of the mountain range. Some researchers say this episode is a reactivation of rift that was formed during the Gondwanide Orogeny, but it has never been proven.
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The top (youngest) layer is composed of Mount Toby Conglomerate. About 200 million years ago, as the continent of North America began rifting apart from Africa and Eurasia, a series of erosion and deposition episodes interspersed with heavy basalt lava flows created this layer cake. Faulting and earthquakes tilted the layers diagonally; subsequent erosion and glacial activity exposed the tilted "layers" of sandstone, basalt, and erosion-resistant conglomerate visible today. Although not composed of trap rock, Mount Toby is a closely associated with the trap rock Metacomet Ridge by virtue of its origin via the same rifting and uplift that created those mountains.
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Volcanism accompanied the rifting and continued into the Pleistocene. The sediments deposited in the basin are affected by numerous intrusions. The area was the first where peperites were described, from a basaltic intrusion into lacustrine limestone. de Goer de Herve, A. 2008.
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Sedimentation from the GLTZ-rifting environment continued into the Penokean orogeny, which is the next major tectonic event in the Great Lakes region. Several earthquakes have been documented in Minnesota, Michigan's Upper Peninsula and Sudbury in the last 120 years along the GLTZ.
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The ranges formed during the Delamerian orogeny continue to erode, and intra-plate subsidence is occurring. In the South Mount Lofty Ranges this has resulted in rifting and the formation of graben structures, creating the long parallel faults which shape the Adelaide Plains.
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Hyperextended rifting is the name for this phenomenon. The mantle rock is peridotite. The peridotite had been formed from a melt, that was depleted in crustal materials, but then was re-enriched in plagioclase felspar. The mantle exhumation occurred in two phases.
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Northeast China is the site of major Cenozoic volcanism. The Pacific Plate subducts beneath the Eurasian Plate, generating volcanic activity. This subduction process along with back-arc spreading and continental rifting triggers volcanic activity in the region. Geothermal resources are also widespread.
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At the beginning of the Mesozoic, the Aaiun-Tarfaya coastal basin filled with clastic material and evaporate deposits, as well as basalt extruded during rifting. Marine transgression in the Jurassic formed carbonate, marl and clastic sequences, overlain by additional clastic sequences from the Cretaceous.
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Tectonics of the Richmond Gulf area, northern Quebec-a hypothesis. Current research, part C. Geological Survey of Canada, Paper, pp. 59-68.Chandler, F.W. and Parrish, R.R., 1989. Age of the Richmond Gulf Group and implications for rifting in the Trans-Hudson Orogen, Canada.
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The pattern of sedimentation from this rifting environment continued into the Penokean orogeny, which is the next major tectonic event in the Great Lakes region. During the Penokean orogeny (1,850 to 1,900 million years ago), compression deformed the sequences in the Lake Superior region.
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The results were interpreted as suggesting continental rifting during the Eocene, perhaps a failed rift basin, But questioned by others. See , p. 9, and also . possibly connected with the rotation of the Klamath Mountain block away from the Idaho Batholith (see Oregon rotation, below).
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At the onset of rifting, the upper part of the lithosphere starts to extend on a series of initially unconnected normal faults, leading to the development of isolated basins. In subaerial rifts, drainage at this stage is generally internal, with no element of through drainage.
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The Chott el Fejej is a typical chott, or dry lake, of the Sahara. It is underlain, however, by a major anticline known as the Fejej Dome. This anticline and other surrounding structures are argued to be the result of rifting in the Cretaceous period.
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The later lava domes are of trachydacitic-rhyolitic composition. Southeast of Jorquera lies the Carrizalillo caldera. The formation of the caldera is linked to the geological history of the Copiapo ranges. After Cretaceous-Paleogene episodes of rifting during the Paleocene-Eocene caldera and stratovolcano occurred.
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The cause of asymmetric spreading in back-arc basins remains poorly understood. General ideas invoke asymmetries relative to the spreading axis in arc melt generation processes and heat flow, hydration gradients with distance from the slab, mantle wedge effects, and evolution from rifting to spreading.
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This implies that the Iceland hotspot may be much older than the earliest rifting of what is now the northernmost Northeast Atlantic. If this is true, then much of the rifting in the North Atlantic was likely caused by thinning and bulging of the crust as opposed to the more direct influence of the mantle plume which sustains the Iceland hotspot. In other scientific work on the path of the Iceland hotspot, no such westward track toward Canada (where the aforementioned older igneous rocks exist) can be detected, which implies that the older igneous rocks found in the Northern Atlantic may not have originated from the hotspot.
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Various models have Siletzia forming inshore, on or near the continental margin. While all current models have Siletzia rifting away from the continent after accretion or formation, a subclass of "rifted" models consider the rifting to have caused the Siletzia eruptions. proposed that the Siletzia basalts might have "leaked" through transform faults (perpendicular to a spreading ridge) during changes in direction of the tectonic plates. The size of these eruptions and their location in this region is attributed to proximity to the Yellowstone hotspot.. This "leaky transform" theory seems to be largely rejected, likely because the plate motion model it was based on was shown to be faulty.. Wells, et al.
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The second phase of rifting occurred in the late Jurassic—extension shifted from a wide-rift mode that encompassed future proximal margins, and it focused at distal margins where continental crust eventually. Throughout the complete formation of the basin, from the Late Triassic to the Cretaceous, four phases of rifting can be defined. This first phase occurred during the Late Triassic to the Early Jurassic and is characterized by symmetrical grabens and half- grabens and is concentrated in the central areas of the basin. During the Early Jurassic, the second phase is characterized by minor salt movements along most substantial faults and occurs south of the substantial, centrally- located Nazare fault.
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A craton (, , or ; from kratos "strength") is an old and stable part of the continental lithosphere, which consists of the Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates; the exceptions occur where geologically recent rifting events have separated cratons and created passive margins along their edges. They are characteristically composed of ancient crystalline basement rock, which may be covered by younger sedimentary rock. They have a thick crust and deep lithospheric roots that extend as much as several hundred kilometres into the Earth's mantle.
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The volcano is made of volcanic bombs and cinders with a crater at its summit where a churning lava lake poured and overflowed its rim during the 18th century.Nisga'a Memorial Lava Beds Provincial Park Retrieved on 2008-02-13 Volcanism at the Tseax Cone is caused by the rifting of the Earth's crust where two parts of the North American Plate are breaking apart. The rifting is the result of the Pacific Plate sliding northward along the transform Queen Charlotte Fault, on its way to the Aleutian Trench.Catalogue of Canadian volcanoes – Stikine volcanic belt Retrieved on 2008-02-13 The lava emitted in eruptions at the Tseax Cone is fluid.
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The rifting of cratons produced intracratonic basins and passive margin. Extensional periods were interrupted by orogenies, uplift, magmatism, and hydrothermal activity, ultimately creating the landscape seen today. Thus, the rocks exposed in the Wernecke mountains reveal the events responsible for the early formation of western North America.
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The volcanism was so extensive that in the late Cretaceous Madagascar may have been entirely covered in flood basalts from volcanism associated with this second rifting event. It was at this point in the end of the Cretaceous that Madagascar became entirely isolated from any other continent.
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See also . Mantle plumes and slab windows both feature voluminous magmatism; the main difference is that slab windows would form only where the spreading ridge is subducted. This implies formation at the continental margin, and then rifting, in the manner of the second class of models.
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AAPG Studies in Geology. vol. 31 American Association of Petroleum Geologists, Tulsa,Oklahoma.Macdonald, D.I.M., P.A. Doubleday, and S.R.A. Kelly (1999) On the origin of fore-arc basins; new evidence of formation by rifting from the Jurassic of Alexander Island, Antarctica. Terra Nova. 11(4):186–193.
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The two most important factors for the existence of Iceland, rifting in combination with a hot spot, an upwelling of unusual quantities of magma from the mantle, were also responsible for the existence of Reykjanesskagi.Thor Thordarson, Armann Hoskuldsson: Iceland. Classic geology of Europe 3. Harpenden 2002, p.
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In the uppermost Oligocene and lower Miocene rifting started, and continental deposits were made. followed by marine deposits on a shallow shelf. During this period the trough grew by extension to its present dimensions. In the middle and Upper Miocene clastic sediments were deposited under sea water.
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The exposed clastic sedimentary rocks, as well as volcanic and carbonate units record rifting and subsidence of the Superior craton during this period. There are two main volcanic sequences on the Belcher Islands called the Eskimo and overlying Flaherty volcanics. These volcanics form part of the Circum-Superior Belt.
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Examples of rifting include the 300 foot wide Medford dike and the faulting of the western margin of the Avalon terrane to form the Middleton Basin, both in the Jurassic. Triassic and Jurassic-age plant fossils are found in the arkose, conglomerate and shale of the Middleton Basin.
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The Taconic-Acadian deformation was caused by the collision of an ocean floor/island arc terrane with a continental margin or fringing microcontinent in the early Paleozoic. The Alleghanian-Pallisades deformation was caused by continental rifting in the early Mesozoic, and possibly late- Paleozoic trans-current plate motions.
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Transitional crust, separating true oceanic and continental crusts, is the foundation of any passive margin. This forms during the rifting stage and consists of two endmembers: Volcanic and Non-Volcanic. This classification scheme only applies to rifted and transtensional margin; transitional crust of sheared margins is very poorly known.
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The Lancaster Aulacogen is a geological structure underlying Lancaster Sound and Prince Regent Inlet in the Arctic Archipelago of Nunavut, Canada. It formed as a result of extensional tectonics during the Eurekan Rifting Episode, which took place in the Canadian Arctic Rift System from the Cretaceous to the Tertiary.
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The acidic volcanism that created the KGF sequence is associated with plutonic intrusions during the Middle Jurassic-Early Cretaceous in the northern Antarctic Peninsula. These plutonic intrusions could have been caused by the doming and rifting in the continental margin of Gondwana at the onset of oceanic slab subduction.
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During the Mesoproterozoic Era, another rifting phase began.Deb, M., Talwar, A.K., Tewari, A., Banerjee, A.K., 1995. Bimodal volcanism in South Delhi fold belt: a suite of differentiated felsic lava at Jharivav, north Gujarat. In: Sinha-Roy, S., Gupta, K.R. (Eds.), Continental Crust of NW and Central India. Geol. Soc.
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The West African coast has several structural basins, along with counterparts along the South American margin, which formed during the Late Jurassic to Albian-Cenomanian rifting associated with the breakup of Gondwanaland.Pauken, R.J., 1992, Sanaga Sud Field, Offshore Cameroon, West Africa, In Giant Oil and Gas Fields of the Decade, 1978-1988, AAPG Memoir 54, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists, During rifting, fluvial and marine clastic rocks plus evaporites were deposited. The Sanaga Sud Field, located in the Douala Basin, was discovered with the Sanaga Sud A-1 well in 1979, and produces from Lower Cretaceous shales and sands overlain by Upper Cretaceous shales. The gas-water contact shows up as a seismic amplitude event. .
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Tectonic and magmatic features associated with the Mackenzie Large Igneous Province. Red star shows the initial Mackenzie plume zone relative to the lithosphere; partial black circle is the estimate of the zone of plume influence on stress- field orientation; dark lines are dikes of the Mackenzie swarm; CRB indicates the Coppermine River basalts; M indicates the Muskox intrusion. At the beginning of the Mackenzie magmatic event, the Mackenzie hotspot collided with lithosphere that was already in an extensional regime that allowed rifting to occur. Passive rifting has been interpreted as the mechanism that produced the opening of the former Poseidon Ocean, the geometry of which would have been partly controlled by dike swarm geometry.
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In the begin of the late Triassic, high volumes of sediments accumulate off of the shoreline of western Australia to the northern extend of the Exmouth Plateau by the Mungaroo Deltas. The Carnian (237-228 Ma) to Norian (228-209 Ma) aged fluviodeltaic sediments deposited were siliciclastic claystones and sandstones, and detritus which would late make up the coals found in Mungaroo Formation. As extensional rifting between Greater Indian and the Australian continued, magmatic intrusion along the westernmost section of the Exmouth Plateau caused further rifting to the outer margins. By the end of the Late Triassic (209-201 Ma) tectonic activity had relatively slowed down and less deltaic sediments were deposited compared to the Carnian and Norian.
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The second is an early Miocene (roughly 17 million years ago) rifting event which produced half grabens composed of west tilted blocks and east dipping normal faults which extended the basin between 3–5 km. Faulting resulted in the uplift of the western flank and southeastern corner of the Adare Trough, and subsidence south and southwest of the trough. The tilted blocks align in a northeast-southwest direction that starts south of the Adare Trough and heads toward Cape Adare. Faulting reached the shelf edge, indicating that this event was probably linked with rifting activity outside the basin, most likely with the east dipping faulting in the Northern Basin, a neighboring sedimentary basin in the Ross Embayment.
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Farther south are two more well-known volcanoes, Mount Discovery and Mount Morning, which are on the coast across from Mount Erebus and Mount Terror on Ross Island. The volcanism in this area is caused by rifting along a number of rift zones increasing mainly north-south similar to the coast. Marie Byrd Land contains the largest volcanic region in Antarctica, covering a length of almost along the Pacific coast. The volcanism is the result of rifting along the vast West Antarctic Rift System, which extends from the base of the Antarctic Peninsula to the surrounding area of Ross Island, and the volcanoes are found along the northern edge of the rift.
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Evidence is showing that the East African Rift System is a classic continental-continental rifting event but the extent of research due to its age and continuing formation is diverse and filled with many hypothetical models that support and contrast each other. The rifting began in the Paleogene due to the far-field stress from the subduction of the Arabian plate under the Eurasian plate and the mantle upwelling that has been seen to move over time because of the multiple area of hot spots around the EARS. This crustal uplift has created extension and horst and grabens and even listric faults which indicate a pre- oceanic basin structure. The future of this area is unknown.
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The continent ocean transition (COT) is wide on the north side and on the southern side where the plateau is flanked by the Diamantina Fracture Zone. Before India broke off from Australia-Antarctica at 127 Ma the Naturaliste Plateau was flanked by what would become two microcontinents, the Batavia and Gulden Draak Knolls, now located on the western margin of the Perth Abyssal Plain from Australia. South of the plateau, during some 45 Ma after India and the two knolls broke off, rifting occurred between the plateau and the Bruce Rise, now located off Antarctica. This rifting continued until sea-floor spreading began 83 Ma. Continental metamorphic and granitic basement rocks have been dredged from both knolls.
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The formation of the Red Sea – Gulf of Suez rift system was caused by the anticlockwise rotation of the Arabian Plate with respect to the African Plate. This model is consistent with near orthogonal rifting along the entire length of the rift system. Alternative models that suggest initiation by strike-slip faulting and pull-apart basin development along the axis of the rift have not been supported by detailed studies of the rift geometry. Towards the end of the Miocene, the Arabian Plate began to collide with the Eurasian Plate leading to changes in the plate configuration, the development of the Dead Sea Transform and cessation in rifting in the Gulf of Suez.
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Although extensive rifting has not yet been recognized in the Northern Cordilleran Volcanic Province, volcanism throughout the past 1.6 million years is possibly due to repetitive upper mantle upwelling and adjacent transtension throughout the Queen Charlotte Fault, accommodated partly by numerous east-west trending fault zones that extend all through the Northern Cordilleran Volcanic Province. The volcanics comprising the Northern Cordilleran Volcanic Province are consistent with the rifting environment. Alkaline basalt, lesser hawaiite and basanite magmas from effusive eruptions create the massive shield volcanoes and small cinder cones throughout the volcanic province, several of which comprise lherzolite magma. Felsic magmas from more viscous eruptions create the massive central volcanoes and largely consist of trachyte, pantellerite and comendite lavas.
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The tectonic events and basin developmental phases are thought to be correlated to the amalgamation and breakup of plates during supercontinent cycles of Columbia, Rodinia, and Gondwana. The Aravalli orogeny (~1,800 Ma) began with the development of oceanic basin. The rifting process is believed to be associated with the formation of the Columbia supercontinent, which happened from 2.5 Ga to 1.8 Ga and was coeval with the onset of Aravalli orogeny's rifting basin. The opening of another sedimentary basin during the Delhi orogeny (~-1,100 Ma) coincided with the time where the supercontinent Columbia broke up, and the cessation of basin development followed by a compressional phase was concurrent with the assembly of Rodinia.
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The newfound space for sediments to accumulate was introduced by Eocene rifting. Erosional material sourced from the Borneo highlands along with other older parts of the basin margins being uplifted . Cenozoic magmatism mentioned below that caused intrusions such as at Mt. Kinabalu could be potentially related to this regional uplift.
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The Western Cape lies on the Cape Fold Belt, which is characterised by many thrust faults. Some of these thrust faults were reactivated during Cretaceous rifting as extensional faults, such as the Worcester Fault, which comes to the surface close to the epicentral area, but does not appear to be active.
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The Towaco Formation can be characterized as a continuation of the Passaic Formation, which is mostly playa and alluvial fan deposits resulting from the rifting of Pangea. The primarily red color of this formation is often evidence that the sediments were deposited in arid conditions.Faill, R.T., (2004). The Birdsboro Basin.
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The Feltville Formation can be characterized as a continuation of the Passaic Formation, which is mostly playa and alluvial fan deposits resulting from the rifting of Pangea. The primarily red color of this formation is often evidence that the sediments were deposited in arid conditions.Faill, R.T., (2004). The Birdsboro Basin.
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The south-east corner of the province borders Malawi to its east and Mozambique to its south. Luangwa Valley rifting the highlands dividing Zambia and Malawi, is located in the region. A small portion of Nyika Plateau above Lake Nyasa is located in the northern portion of the province.Mwakikagile 2009, p.
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Around 25 Ma B.P, the Pacific plate started to drift away from the Australian plate, thus splitting the volcanic ridge. The rifting was initially caused by extension until 6 Ma B.P, by which time seafloor spreading started in this region and eventually formed the Lau Basin between the separated ridges.
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This tectonic grain, including the 2.62 Ga Oregon Trail structure, controlled the locations and orientations of Proterozoic rifting and uplifts related to the Laramide orogeny. If there has been any net crustal growth of the Wyoming Province since 3.0 Ga, it has involved a combination of mafic underplating and arc magmatism.
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Plate tectonics- Plate tectonics- The Mesozoic extended roughly from . After the vigorous convergent plate mountain-building of the late Paleozoic, Mesozoic tectonic deformation was comparatively mild. Nevertheless, the era featured the dramatic rifting of the supercontinent Pangaea. Pangaea gradually split into a northern continent, Laurasia, and a southern continent, Gondwana.
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The estimated energy released by the Araguainha impact is insufficient to be a direct cause of the global mass extinction, but the colossal local earth rifting would have released huge amounts of oil and gas from the shattered rock. The resulting sudden global warming might have precipitated the Permian–Triassic extinction.
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These felsic volcanics are understood to have been created by fractionation of mainly alkali basalt magma in crustal reservoirs. An area of continental rifting, such as the Northern Cordilleran Volcanic Province, would aid the formation of high-level reservoirs of capable size and thermal activity to maintain long-lived fractionation.
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This is most likely due to the age of the slab. As oceanic crust gets older it becomes denser resulting in a steeper angle of descent. The thinning of the overriding plate at the back-arc (i.e., back-arc rifting) can lead to the formation of new oceanic crust (i.e.
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The break-up of Pangea resulted in the break-up of the Paleozoic metamorphic basement rock. The basement rock formed half-grabens where eroded sediments from the break-up were then deposited. These sediments created the metasedimentary rocks of the La Quinta formation. Development of the passive margin occurred after rifting.
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56-54 Ma. Continuing research also indicates that continental plate movement (Eurasian, Greenland, and North American), that regional rifting events, and that seafloor spreading between Labrador and Greenland may have begun as early as ca. 95-80 Ma, ca. 81 Ma, and ca. 63-61 Ma respectively (late Cretaceous to early Paleocene).
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During the Triassic the state experienced rifting as Pangaea broke apart. Later, during the Cretaceous, the state was again partially submerged by seawater, where marine vertebrates flourished. On land the state was home to subtropical forests. The sea covering southern Alabama remained in place during the early part of the Cenozoic era.
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Pangea broke apart after 70 million years. The supercontinent was torn apart through fragmentation, which is where parts of the main landmass would break off in stages. There were two main events that led to the dispersal of Pangea. The first was a passive rifting event that occurred in the Triassic period.
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Lau Basin is a young basin (<= 5 m.y. old) that separates a previously continuous island arc by extensional rifting. During the Pliocene, the Pacific plate was subducting beneath the Australian plate. The slab of the Pacific plate melted as it was thrust down, and then rose to form the original Tonga-Kermadec Ridge.
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Taixinan Basin is located on the continental shelf, on the margin of the continental crust. Its tectonic evolution can be divided in three periods. The first period was from Paleocene to Oligocene. Starting in the Paleocene, Taixinan Basin had been experiencing the effect of rifting, which eventually caused the formation of the basin.
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CAMP activity is apparently related to the rifting and breakup of Pangaea during the Late Triassic through Early Jurassic periods, and the enormous province size, varieties of basalt, and brief time span of CAMP magmatism invite speculation about mantle processes that could produce such a magmatic event as well as rift a supercontinent , .
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The southwestern portion of Laurentia consists of Precambrian basement rocks deformed by continental collisions (violet area of the image above). This area has been subjected to considerable rifting as the Basin and Range Province and has been stretched up to 100% of its original width. The area contains numerous large volcanic eruptions.
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The rifting apart of the supercontinent Gondwana in the Late Paleozoic created failed rift grabens. The rifting process stalled and then continued in the Triassic until the Middle Jurassic as between two and six kilometers of clastic sediments accumulated on the western margin of the Seychelles microcontinent. Along the passive northwest margin with Gondwana, the coastline was submerged and one kilometer of fine sediments deposited there as the Somali oceanic basin formed East Gondwana fragmented 120 million years ago, splitting up Antarctica- Australia and Madagascar-Seychelles-India, which ultimately separated 85 million years ago as the Mascarene basin formed. The Deccan Traps hotspot, which poured out immense basalt flows in India 65 million years ago and ultimately formed islands such as Mauritius and Réunion, isolated Seychelles.
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Beneath the sediments of the Gulf of Mexico basin, most of the pre-Triassic basement rocks are believed to be allochthonous thrust sheets sutured during the formation of Pangaea. However, it was during the break-up of the supercontinent that the foundation for the Gulf of Mexico sediments would be laid. Prior to the rifting which formed the Gulf of Mexico basin, extensional deformation in the Late-Triassic caused by the breakup up of Pangaea, and more specifically the rifting of the Atlantic Ocean, created basement graben formations which filled with terrestrial red bed sediments, and volcanic sediments from the eruption of the Central Atlantic Magmatic Plume. The plume erupted 60,000 cubic kilometers of flood basalts over ancestral North and South America, Africa and parts of Europe.
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Faulting and earthquakes during the period of continental rifting tilted the layers diagonally; subsequent erosion and glacial activity exposed the tilted layers of sandstone, basalt, and conglomerate visible today as three distinct mountain masses. Although Mount Toby and Mount Sugarloaf are not composed of traprock, they are part of the Metacomet Ridge by virtue of their origin via the same rifting and uplift processes. Of all the summits that make up the Metacomet Ridge, West Rock, in New Haven, Connecticut, bears special mention because it was not formed by the volcanic flooding that created most of the traprock ridges. Rather, it is the remains of an enormous volcanic dike through which the basalt lava floods found access to the surface.
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Large offshore sandstone deposits suggest a high-energy shallow water environment during the early Jurassic. The Harstad, Tromsø, Bjørnøya and Sørvestsnaget basins all developed during the late Jurassic and into the Cretaceous as the rifting which formed the Atlantic ocean propagated northward and began to open the Norwegian Sea. Fine-grained clastic rock filled in the Vøring and Møre basins by the mid-Cretaceous while coarser material continued to fill in the Vøring basin during the Cenomanian and Campanian. The rifting which finally completed the opening of the sea from 60 to 55 million years ago created the Utgard High and Fles Fault Complex, uplifted southwestern Norway and led to the eruption of large volumes of lava for almost six million years.
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The Northern Cordilleran Volcanic Province rift The Mount Edziza volcanic complex began forming about 7.5 million years ago and has grown steadily since then. Like other volcanoes in northwestern British Columbia, the Mount Edziza volcanic complex has its origins in continental rifting—a long divergent plate boundary where the lithosphere is being pulled apart. Here, the continental crust of the North American Plate is being stretched at a rate of about per year. This incipient rifting has formed as a result of the Pacific Plate sliding northward along the Queen Charlotte Fault, on its way to the Aleutian Trench, which extends along the southern coastline of Alaska and the adjacent waters of northeastern Siberia off the coast of Kamchatka Peninsula.
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A critical turn in Burke's career occurred in 1972–1973 when he became a visiting professor at the University of Toronto, Canada. There, he became a close associate of J. Tuzo Wilson, who at that time was one of the most prominent proponents of plate tectonics and studies of volcanic hotspots. During his time in Toronto with Wilson, Burke began a lifelong study of hotspots, rifting and mantle processes, which was enhanced by his previous field experiences in Africa and the Caribbean. In 1973, Burke was invited by John F. Dewey to join the faculty at the State University of New York at Albany, which had assembled a group of geoscientists interested in plate tectonics, hotspot studies, rifting, and field-based ophiolite studies.
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Basin Geometry and Architecture of a Tethyan Passive Margin, Southern Alps, Italy: Implications for Rifting Mechanisms: Chapter 13: African and Mediterranean Margins. It is known due to the exquisite preservation observed on the Outcrop on Osteno, where several kinds of marine biota have been recovered.Pinna, G. (1985). Exceptional preservation in the Jurassic of Osteno.
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It is the youngest of the beds being between Late Jurassic and Early Cretaceous. It occurs from Grafton to Casino consisting of soft sandstone, siltstone and claystone. Dolerite has intruded this at Glenugie Peak, and near Banyabba. Rifting along the east coast of Australia commenced and uplifted the eastern side of the Clarence Moreton Basin.
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Impact cratering also had consequences for both the development of plume-induced subduction and the establishment of global plate tectonics. The steepening of geothermal gradients could have directly enhanced convective mantle transport which now beneath an increasingly fractured lithosphere could have created stresses great enough to cause rifting and the separation of crust into plates.
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The Tehtys phase occurred in the late Triassic and continued in the Early Jurassic. During this time the Jeanne d'Arc Basin was formed due to rifting forming half grabens as major crustal detachment occurred. This phase is most important phase in the construction of the Jeanne d'Arc Basin as it gave it its size.
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The Stockton is described as a bajada. The sediments were a result of the rifting of Pangea. The sediments came from the southeast from a largely granitic terrane and spread across an even plain. Interfingered with the Stockton, the Lockatong Formation are lake sediments, which grew during wetter climatic cycles during the Late Triassic.
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During the break-up of Pangea, the North American plate began to separate from the South American plate. The two plates rifted away from each other forming the "Proto-Caribbean Seaway", an 1800 km wide region of oceanic crust. As this rifting occurred, the Caribbean plate began its eastward migration from the Pacific region.
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During the late Cretaceous, more extension occurs in this region, which creates syn-rift troughs. This extension forms the central depression, which is an integral part of the petroleum system, and is the location of nearly all of the oil/gas fields in the Gippsland Basin. Also during the late Cretaceous, volcanism occurred due to the Tasman Sea rifting.
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They are cut by deep troughs across. These troughs are an example of continental rifting, and are evidence of surface tectonism. Beta Regio is cut by a radar-bright north-south trough called Devana Chasma. The northern end has a volcano called Rhea Mons, and the southern end is dominated by a volcano titled Theia Mons.
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Her more recent pieces have explored the Gondwana schism. In 2003 she completed her work, "Africa Rifting: Lines of Fire, Namibia/Brazil," which featured flowing red material on the sandy beaches of Africa and Brazil. This work was filmed on September 11, 2001 and presents a powerful contrast to the events in the United States at the time.
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The geology of East Timor has been studied onshore and with offshore seismic studies. The region experienced rifting between the Permian and early Cretaceous. Shallow water sediments shifted to deep water sediments by the Triassic. The region was a subsiding passive margin from the Early Cretaceous through the Eocene, experiencing deep water carbonate and shale deposition.
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Extension resulted in the development of NE-SW trending half graben which later lead to rift filled sequence. These half graben were then continuously filled by basin wide deposition of fluvial sediment from the west and thermal subsidence. The rifting phase was follow by a spreading in the seafloor with the axis shifting from WSW to SW trend.
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Erosion continued into the Mesozoic, so the state has almost no rock record from this entire era of geologic time. The few rocks present were igneous and likely formed as a result of the rifting that divided Pangaea. No dinosaur fossils have ever been discovered in New Hampshire. No other fossils are known from this scant rock record either.
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Rifting occurred within and around England, prior to the breakup of the super- continent in the Jurassic period. Rock fragments found near Bristol appear to indicate that in 214 million years ago England was showered with a fine layer of debris from an asteroid impact at the Manicouagan Impact Crater in Canada, although this is still being debated.
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The Lower Rhine Graben or Lower Rhine Embayment, trends NW-SE and continues offshore into structures within the southern North Sea. To the southeast the dominant faults are SW-dipping, while to the northwest they become NE-dipping, in both cases giving it a half-graben geometry. Rifting initiated during the Oligocene and continues to the present day.
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The Bresse Graben lies to the east of the Limagne Graben. It initiated during the Eocene but the rifting stopped during the period from Late Oligocene to middle Miocene, but resumed in the Late Miocene. The eastern margin of the basin was overridden by thrust faults from the Jura Mountains, the leading edge of the alpine thin-skinned deformation.
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26 The natural environment of the area has been shaped largely by its geology. The valley is actually a graben with the oldest rocks being extensively metamorphosed and at least 1.7 billion years old. Ancient, warm, shallow seas deposited marine sediments until rifting opened the Pacific Ocean. Additional sedimentation occurred until a subduction zone formed off the coast.
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Non- marine Tertiary sediments up to approximately thick exist in the Barrow Basin. Lady Franklin Basin is one of the deepest basins offshore West Greenland. It was established during Early Cretaceous rifting and lies within a fault zone delimiting the northern end of the Labrador Sea. A thick succession of Cretaceous and Cenozoic sediments occupies the Lady Franklin Basin.
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It developed from a transform fault and now operates as a hyper-slow spreading center, as recognized by the relative movement between the African and Eurasian plates.Beier, C., Haase, K. M., Abouchami, W., Krienitz, M. S., Hauff, F. (2008). Magma genesis by rifting of oceanic lithosphere above anomalous mantle: Terceira Rift, Azores. Geochemistry Geophysics Geosystems (G3), 9, Q12013.
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Arrows represent direction of subduction along North America. One of the major events during the Coast Range Arc was about 85 million years ago when a huge rift developed near the center of the oceanic Farallon Plate. This rifting event created the oceanic Kula Plate. It is unknown why such a large rupture of the Farallon Plate occurred.
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Volcano-dominated rises, such as the Bell Regio, have volcanoes atop the topographic rise. Rift-dominated rises are uplifted by rifting and thinning of the lithosphere and include the Beta Regio and the overlying Theia Mons. In a coronae-dominated rise, uplift is caused by the gravitational collapse and extension of a magma chamber, and include the Themis Regio.
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What initiated rifting is unknown. suggested that as the continent overrode the Yellowstone hotspot, the upwelling plume tore away a previously accreted terrane. suggested a change in the rate at which the plates were converging, or the "kinematic effects" (such as a slab window) from the passage of the Kula-Farallon ridge (or Resurrection-Farallon ridge)..
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The collision of small microcontinents like Amuria and the large collision between Asia and Gondwana in the Mesozoic and Cenozoic had a major impact on the region. Crustal extension created the Mongolian Plateau, while rifting, crustal thinning, block faulting and basalt eruptions produced terrain very similar to the Basin and Range province in the western United States.
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Nevertheless, its existence did significantly influence the marine life of its time. In the Cryogenian period the Earth experienced large glaciations, and temperatures were at least as cool as today. Substantial areas of Rodinia may have been covered by glaciers or the southern polar ice cap. Low temperatures may have been exaggerated during the early stages of continental rifting.
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Mesozoic sediments of marine origin occur in the coastal area along the Red Sea. A number of thin Miocene age basalt flows occur within the sediments of this zone whilst the basalts of the Aden Series date from Pliocene to Holocene times, some being extruded at the time of a major phase of uplift and rifting during the Pleistocene.
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The last major event in the history of the Piedmont was the break-up of Pangaea, when North America and Africa began to separate. Large basins formed from the rifting and were subsequently filled by the sediments shed from the surrounding higher ground. The series of Mesozoic basins is almost entirely located inside the Piedmont region.
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Hydrocarbon research on the Khorat Plateau suggests that the Indochina Terrane was a series of continental fault blocks separated by Permian rifting. Marine conditions were common, although the later periods were marked by lagoon and continent conditions and red beds formed. During the Jurassic marine conditions returned. A fossil ammonite was found at one location in eastern Cambodia.
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Wilson is based at Ohio State University where she investigates the Earth's structural architecture, the interaction between ice sheets in Antarctica and the solid Earth and neotectonic rifting. Her research integrates satellite remote sensing, Global Positioning Systems, both airborne and marine geophysical data and microstructural and structural mapping of faults in sedimentary and outcrop rock cores.
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Pangea animation 03 The break up of Pangea occurs during the Kimmerian tectonic phase for most of the Mesozoic, until the early-mid Cretaceous, this marks the start of creating the present position of our continents today. During the Jurassic, rifting activity reaches its maximum and North America starts to move apart from Eurasia following that event in the Cretaceous the southern part of North America starts to open up the Atlantic Ocean with the separation of South America and Africa. At the end of the Mesozoic the North Sea reached its final position where it lies in present day. Throughout the Cretaceous rifting eventually slowed down and came to a halt which later created the North Sea failed rift system because the regional stresses had shifted on to North America.
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The remnant of Tau's caldera is found on the south coast. A 2000-foot cliff marks the north coast of this island. Upolu formed as an elongated basaltic shield volcano due to Late Tertiary to Late Pliocene rifting along a S. 70° E. trend. Remnants of these eruptions are found as inliers and monadnocks forming Mt. Tafatafao, Mt. Vaaifetu, and Mt. Spitzer.
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The Kutai is an extensional basin in a general foreland setting. Its geologic evolution begins in the mid Eocene and involves phases of extension and rifting, thermal sag, and isostatic subsidence. Rapid, high volume, sedimentation related to uplift and inversion began in the Early Miocene. The different stages of Kutai basin evolution can be roughly correlated to regional and local tectonic events.
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The North America/Pacific-Monterey transform boundary began to move north and created crustal extension. This rifting was accompanied with the rotation of the western Transverse Ranges. This rotation is responsible for the placement and northwest-southeast orientation of the LA Basin. Early in the Miocene, before deposition of the Topanga, high heat flow and transtension caused the extension of the basin.
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The Huronian and Marquette Range supergroups are similar sedimentary groups to the Animikie Group; all three are in the Great Lakes region. Rifting of continental plates create sedimentary basins; the largest of these basins in the Great Lakes area are the Animikie Group in Minnesota, the Marquette Range Supergroup in northern Michigan and Wisconsin, and the Huronian Supergroup in eastern Ontario.
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1–43 In contrast, the era featured the dramatic rifting of the supercontinent Pangaea, which gradually split into a northern continent, Laurasia, and a southern continent, Gondwana. This created the passive continental margin that characterizes most of the Atlantic coastline (such as along the U.S. East Coast) today.Stanley, Steven M. Earth System History. New York: W.H. Freeman and Company, 1999.
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The rifting started in the Late Eocene and the main phase of subsidence continued into the Late Oligocene.Ziegler, P.A. 1990. Geological Atlas of Western Europe, Geological Society London, 256pp. The Limagne Graben forms part of a system of linked rifts, including the Rhine Graben, known as the European Cenozoic Rift System, that formed in response to compressional deformation of the Alpine foreland.
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The Boonton Formation can be characterized as the uppermost continuation of the Passaic Formation, which is mostly playa and alluvial fan deposits resulting from the rifting of Pangea. However, unlike the Passaic Formation, which is primarily red in color due to arid conditions at the time of deposition,Faill, R.T., (2004). The Birdsboro Basin. Pennsylvania Geology V. 34 n. 4.
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At the same time, crustal extension took place because the mountain range was isostatically unstable (this is called orogenic collapse). Due to extension, basins formed along the axis of the mountain range and felsic volcanism occurred. This was the first phase of rifting between Europe and Africa. Due to the rising sealevel in the Triassic period, the eastern margin of Pangaea was flooded.
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Illa Grossa, ("Large Island" in Valencian)< is the largest island of the Columbretes archipelago of Spain, located in the Mediterranean Sea. It has a surface area of 14 hectares, or 0.05 square miles. It sits 60 km from Costa del Azahar. The island has experienced a rifting process since the lower Miocene, and is characterized by a significant presence of basalt materials.
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The Bravo Lake Formation in central Baffin Island is a rare alkaline suite that formed as a result of submarine rifting during the Paleoproterozoic period.Volcanology and geochemistry of the Bravo Lake Formation, Baffin Island, Nunavut . Retrieved on 2007-11-06 The lavas of the volcanic belt display geochemical characteristics similar to modern ocean-island-basalt groups. The range from moderately to intensely fractionated.
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The subducting Pacific Plate dips at about 10 degrees and directed 83 degrees west of north. The northern subduction zone is expanding by rifting while the southern contains a strike slip fault. Seismologists have been studying how the subducting slabs underneath the Mariana island arc are entering the lower mantle and being redirected horizontally, deflecting off the upper to lower mantle transition zone.
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The Baoban Group generally showed greenschist and amphibolite facies metamorphism which could also be separately identified as the Upper Ewenling Formation and the Lower Gezhencun Formation. During Paleoproterozoic and Mesoproterozoic, the Island was in a spreading arc basin system. The rifting provided a depositional environment for the Baoban Group in ca. 1800–1450 Ma. It was then intruded by Mesoproterozoic granites at ca.
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The region is known as the Bondy and LaCoste domical complexes. In the southwestern Metasedimentary Belt, the rocks are tonalitic to granitic orthogneisses. Nd model ages of the Central Metasedimentary Belt range from 1.55-1.4 Ga. The origin of this area can be attributed to rifting (which made the accommodation for the sediments) and subsequent thrusting from the collision with Amazonia.
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Opening of Central and North Atlantic from 170 million years ago to the present. Middle figure shows Eurekan rifting between Greenland and the Labrador Peninsula 100 million years ago. Extending several hundred kilometres through Crozier Strait is the Crozier Strait Fault Zone. It lies within a north-trending anticline of the Cornwallis Fold Belt and appears to contain a downdropped fault block.
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Stikinia, or the Stikine terrane, is a terrane in British Columbia, Canada; the largest of the Canadian Cordillera. It formed as an independent, intraoceanic volcanic arc during the Paleozoic and Mesozoic. Stikinia forms the bedrock of numerous volcanoes in the southern portion of the Northern Cordilleran Volcanic Province (NCVP), a Miocene to Holocene geologic province that has its origins in continental rifting.
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Fuis, Gary S. and Walter D. Mooney, Salton Trough Lithospheric Structure and Tectonics from Seismic- Refraction and Other Data in USGS Professional Paper 1515 Both of these are transform faults in the northern leg of the East Pacific Rise system that runs the length of the Gulf of California and is steadily rifting the Baja California Peninsula away from the mainland of Mexico.
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The Mississippi Interior Salt Basin underlies southern and west-central Mississippi with up to 3000 feet of Late Jurassic salt and 50 shallow salt domes. It formed during the beginnings of the Gulf of Mexico during the breakup of Pangea. Triassic igneous sills injected into shales in the Black Warrior Basin during the rifting process. Salt deposition ended by 150 million years ago.
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Uplift associated with the rifting altered the connections among the region's water bodies. About 13,000 to 9,000 years ago, volcanic activity blocked Lake Kivu's former outlet to the watershed of the Nile. The volcanism produced mountains, including the Virungas, which rose between Lake Kivu and Lake Edward, to the north. Water from Lake Kivu was then forced south down the Ruzizi.
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The first phases of Andean orogeny in the Jurassic and Early Cretaceous were characterized by extensional tectonics, rifting, the development of back-arc basins and the emplacement of large batholiths. This development is presumed to have been linked to the subduction of cold oceanic lithosphere. During the mid to Late Cretaceous (ca. 90 million years ago) the Andean orogeny changed significantly in character.
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This once-active divergent plate boundary became the passive, trailing edge of westward moving North America. In plate tectonic terms, the Atlantic Plain is known as a classic example of a passive continental margin. During the rifting, South America tore away from North America and headed southward. The ocean flooded into the opening between the two continents, forming the Gulf of Mexico.
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After that, the formation of structural folds and faults in the reservoir rocks leads to the natural creation of zones where the natural resources become trapped and stored as reserves that are commercially recoverable. Four major tectonic events resulted in the formation of structural traps: # The Carboniferous Hercynian Orogeny. # Early Triassic Zagros Rifting. # The First or Early Oman Alpine Orogeny.
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Most occurrences of bimodal volcanism are associated with thinning of the crust and the presence of such rocks in metamorphic sequences has been used to provide evidence for past rifting events.Brewer, T.S., Ahall, K-L., Menuge, J.F., Storey, C.D. & Parrish, R.R. 2004. Mesoproterozoic bimodal volcanism in SW Norway, evidence for recurring pre-Sveconorwegian continental margin tectonism, Precambrian Research, 134, 249–273.
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In order for a lake to become alkalic, a special combination of geographic, geological and climatic conditions are required. First of all, a suitable topography is needed, that limits the outflow of water from the lake. When the outflow is completely prevented, this is called an endorheic basin. Craters or depressions formed by tectonic rifting often provide such topological depressions.
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Where full rifting occurred, the Atlantic Ocean was created. It is important to note that along these rifts, magmatic activity never stopped, as shown by the ongoing eruption of lava along the Mid-Atlantic Ridge. The Fundy Basin is one in a series of these failed rifts. During its rupture, tholeiitic basaltic lava erupted, producing a sequence of continental tholeiitic basalts.
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Surrounding geological structures. The Lusitanian Basin results from the opening of the North Atlantic Ocean due to Mesozoic extension. Rifting was initiated between Newfoundland and Iberia and occurred primarily in two phases. The initial phase occurred in the Late Triassic–earliest Jurassic followed by an episode of faulting and basin subsidence during the early to middle Jurassic south of the Nazare Fault.
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Winter sea ice coverage was much more limited in the south. Geologically, the Cenozoic is the era when the continents moved into their current positions. The Alpine Orogeny, the spreading of the Mid Atlantic ridge, and the creation of the Atlantic Ocean basin occurred in the Cenozoic era. The Iceland hot spot and North Atlantic rifting helped to exhume the British Isles.
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This collision formed Laurussia. The Variscan (Rheic) plate cycle resulted in the formation of Pangaea when Gondwana and Laurussia collided. The elimination of the Rheic Ocean caused the formation of a massive mountain range through the border countries of the present day North Sea. Triassic and Jurassic volcanic rifting and graben fault systems created highs and lows in the North Sea area.
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A total of four orogenies have affected the rocks of the Commonwealth including the Grenville orogeny, the Taconic orogeny, the Acadian orogeny, and the Appalachian orogeny. The Appalachian event has left the most evidence and has continued to shape the landscape of the state. The Pennsylvania terrain has also been affected by continental rifting during the Mesozoic era.Schultz, C.H. ed.
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These rocks eventually provided the platform for the deposition of sediment that would become the Wissahickon Formation during a rifting of Rodinia. Sea floor spreading continued until a passive margin developed along the new Iapetus Ocean and a beach strandline developed. These sediments eventually became the Chickies Formation. Siliclasitc and carbonate deposition continued through the Cambrian and into the Ordovician period.
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Another rifting event established the Mayilashan ocean basin and back-arc basin in east Junggar during Silurian. However, the compressional environment restricted the two landforms so that they ended up shut and folded in the late Silurian. This eventually led to the convergence of Tarim, Kazakhstan and Siberian paleo-plates. They were from the original Xinjiang paleocraton that puzzled each other again.
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The first phases of Andean orogeny in the Jurassic and Early Cretaceous were characterized by extensional tectonics, rifting, the development of back-arc basins and the emplacement of large batholiths. This development is presumed to have been linked to the subduction of cold oceanic lithosphere. During the mid to Late Cretaceous (ca. 90 million years ago) the Andean orogeny changed significantly in character.
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At the end of the Cretaceous the basin was stretched by 35 km. In Early Neogene times the basin was inverted as a result of the Pyrenean Orogeny, part of the Alpine Chain formation. This inversion resulted in the formation of mountains called the Iberian Range. Rifting occurred at several different times in the Mesozoic repeating the same pattern of sedimentation.
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These basins were formed by rifting in the Late Triassic (). Further out to sea off the west coast of Spain is the Galicia Bank, which consists of continental crust, and was formerly attached to the Flemish Cap. The Galicia Bank has limestone and marl deposited in shallow water from the Tithonian age. This is capped by dolomite from the Berriasian age ().
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During the Cretaceous, the Zonguldak basin experienced general subsidence, rifting, and faulting. This led to another period of deposition in the region and faulted the coal seams. This faulting provided a pathway for meteoric water to enter the coal seams. During the Aptian, the Intrapontide Ocean, the ocean separating the Western Pontides tectonic region of Turkey form the Sakarya Continent, underwent subduction.
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A ramp basin is a geological depression bounded by a pair of opposite facing reverse faults or thrust faults. In rifting, the equivalent structure is a graben, although the bounding faults are normal rather than reverse in type. Examples of this type of basin include the Cul-de-Sac depression in Haiti and Issyk-Kul in the Tian Shan mountains in Kyrgyzstan.
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Antarctic Peninsula previous plate configurations. As Gondwana broke apart, the Antarctic Peninsula started to take on its modern shape. Roughly 220 million years ago, the continents of Antarctica, South America, and Africa rifted apart. This rifting created low relief basins which allowed for the transport of sediments and subsequent deposition of sedimentary rocks, which happen to be the oldest on the peninsula.
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Evaporites and/or high-pressured shale layers have the ability to flow because of their high mobility and low viscosity characteristics. Rift zones are partially restricted and have limited access to open oceans during rifting period. they are affected by sea level changes and climatic variability. Thick layers of evaporites are formed due to continuous water evaporation and fill of the rift basin.
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This is the most obvious explanation of the observered intraplate characteristics of the alkali basalts, with lherzolite. Alternatively, the bajaites could be formed from partial melting in the mantle of metasomatized mantle apatite and amphibole, followed by postsubduction rifting. This explanation leaves the field untouched by a second subduction episode and leads more naturally to the ocean island basalts that are also present.
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Today, the African Plate is moving over Earth's surface at a speed of 0.292° ± 0.007° per million years, relative to Map of East Africa showing some of the historically active volcanoes(red triangles) and the Afar Triangle (shaded, center) – a triple junction where three plates are pulling away from one another: the Arabian Plate, the African Plate, and the Somali Plate (USGS). The African Plate is rifting in the eastern interior of the African continent along the East African Rift. This rift zone separates the African Plate to the west from the Somali Plate to the east. One hypothesis proposes the existence of a mantle plume beneath the Afar region, whereas an opposing hypothesis asserts that the rifting is merely a zone of maximum weakness where the African Plate is deforming as plates to its east are moving rapidly northward.
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Older crystalline Paleozoic-age strata was extensively faulted and buried below new lake bed sediments or uplifted, as in the case of Mount Warner in Hadley or arkose and sandstone which formed from the erosion of Berkshire schist in the west, together with the Pelham dome, Glastonbury dome and Belchertown pluton. The lake-bed mudstones of the Shuttle Meadow formation preserved dinosaur footprints, as well as fossil fish and insects, which were first noticed in 1802 and became the basis of a large collection at Amherst College. Rifting occurred elsewhere in Massachusetts, with the intrusion of the 300 foot wide Medford gabbro 190 million years ago in the Jurassic or flood basalts and basalt dikes in North Spencer, Holden and Tyngsboro. Although rifting was most pronounced in western Massachusetts, eastern portions of the state also experienced some activity.
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In the central segment rifting started to break Africa in two by opening the Benue Trough around 118 Ma. Rifting in the central segment, however, coincided with the Cretaceous Normal Superchron (also known as the Cretaceous quiet period), a 40 Ma period without magnetic reversals, which makes it difficult to date sea-floor spreading in this segment. The equatorial segment is the last phase of the break-up, but, because it is located on the Equator, magnetic anomalies cannot be used for dating. Various estimates date the propagation of sea-floor spreading in this segment to the period 120–96 Ma. This final stage, nevertheless, coincided with or resulted in the end of continental extension in Africa. About 50 Ma the opening of the Drake Passage resulted from a change in the motions and separation rate of the South American and Antarctic plates.
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Reactive diapirism is the result of regional extension caused by rifting. The overburden becomes weak and thin which allows the salt body to travel upwards. Salt glaciers are a frequent topic in salt tectonics, which is the study of salt causing deformation and its leading cause is differential loading (an unevenly distributed load). Differential loading can be caused by displacement, gravitational and thermal gradients.
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Additionally, it resists erosion better than sandstone and therefore forms prominent structures in the countryside. For example, the peak Brattfjället, highest zone in the park, is situated in one of the largest diabase zones. The diabase is a little less than 300 million years old, which corresponds to the formation of the Oslo Rift. This suggests that these diabases are connected to that rifting event.
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This rift divided Socotra and the Arabian Peninsula; prior to rifting, Socotra was contiguous with what is now the Dhofar Governorate in southern Oman. Extension along the eastern segments of the Aden Ridge increases the separation of the Arabian Peninsula from Somalia (and Socotra) at the rate of about . Additionally, for approximately the last 10 Ma, the associated geologic forces have subjected Socotra to slow tectonic uplift.
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The Western High Atlas preserves evidence of the formation of the Atlantic margin in North Africa. In the Late Triassic, rifting in central Pangaea began to form the Atlantic Ocean. Large alluvial fans began to fill the down-dropped grabens with fluvial sandstones, mudstones and conglomerates, intercalated with evaporite sequences of dolomite, halite and gypsum. A tholeiitic magma series formed dolerite, capping off the Triassic sequence.
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The Comoros island chain in the Mozambique Channel is the result of the rifting of Madagascar away from Africa as well as "hotspot" mantle plume activity. The region is also impact by seismicity and deformation associated with the East African Rift system and the Comoros region is one of the best places in the world to study rift-hotspot interactions. The islands remain volcanically active.
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Crustal movements have created two plate boundary deformation zones between the major plates, the North American Plate and the Eurasian Plate. In northern Iceland, the width of the deformation zone is about 100 km wide. It accumulates strain which come from rifting episodes and larger earthquakes. In southern Iceland, the block located along the plate boundary is identified as a microplate and is named the Hreppar Block.
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Geolines, 14, p. 75-78 In the Upper Jurassic entire Oravic domain began to thermally subside. Since Lowermost Cretaceous time probably an asymmetrical rifting affected the area to the North of the Czorsztyn Ridge where a Magura basin (North Penninic or Valais Ocean equivalent) started to evolve. During the Middle Cretaceous thermal subsidence of the Czorsztyn Ridge caused its development into a pelagic high.
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The Hebridean Terrane forms the westernmost strip of mainland Scotland, most of the Inner Hebrides and all of the Outer Hebrides. Similar rocks are also thought to be present in Shetland and have been proved west and north of the Outer Hebrides by BGS shallow boreholes and hydrocarbon exploration wells. The full extent of this terrane to the west is obscured by the effects of Mesozoic rifting.
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He does not appear to be human and eats rocks for sustenance. She suspects he may be a Stone Eater, a strange race of living statues that can move through solid rock, but she has never seen one move around above the ground before. Later she meets Tonkee, a commless and curious person. Together, they journey south, encountering the vast devastation caused by the "rifting" up north.
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Tectonic and magmatic features associated with the Mackenzie Large Igneous Province, including the rifting that created the Poseidon Ocean. Red star shows the initial Mackenzie plume zone relative to the lithosphere. The Mackenzie hotspot was a volcanic hotspot that existed about 1.3 billion years ago across Canada from the Northwest Territories and Nunavut. It was centred on what is now Darnley Bay on southwestern Victoria Island.
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Hotspot causing rifting of tectonic plates After suturing, the region was tectonically quiet for a few hundred million years. The Algoman Mountains had been built and then eroded into sediments that covered the area. Fragmentation of this Archean supercontinent began around under a hotspot near Sudbury and was completed by around . This is when the Wyoming province is hypothesized to have drifted away from the Superior province.
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This vegetation left behind great coal deposits. This region also has the largest and most diverse fossil tracksites from this time period in the world. Sediments were eroded away from Alabama rather than deposited during the Permian period, so there are no local rocks from this time period. Alabama experienced rifting during the Triassic period of the Mesozoic era due to the breakup of Pangaea.
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Columbia University Press, New York, 2003. . Limited Preview available via Google Books. USGS cross-section of the Newark Basin Erosion began to attack the basin as rifting failed and deposition of new sediments ceased. Over millions of years, erosion ate downward through the tilted rock of the basin, eventually encountering the basalt layers, which are significantly more erosion resistant than the surrounding sedimentary rock.
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The Nipigon diabase sills give evidence of rift-related continental basaltic magmatism during the Midcontinent Rift System event, estimated at 1,109 Ma ago. Thick sills up to thick are also related with the rifting event, forming cliffs that are up to high. The mafic and ultramafic intrusions centered on Lake Nipigon is interpreted to represent a failed arm of the Nipigon embayment.Sutcliffe, R.H., 1991.
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This rifting warmed and rejuvenated the root, giving it the buoyancy to be lifted up to re-establish the mountains as an 800 km long massif. Further uplift still was achieved as deep valleys were later cut erosion lightening the overall mass of the system. Around 35 million years ago, the glaciers merged to form the East Antarctic Ice Sheet, burying the Gamburtsev Range in the process.
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This brought magmatism commonly associated with rifting and doming to the Freemans Cove area. Nearly all magmatic activity was confined to regions within the fault zone and involved the emplacement of dikes, sills, small volcanic plugs and agglomeratic vents. The magmas are chemically bimodal, consisting mainly of nephelinites or larnite-normative nephelinites and basanites along with lesser olivine melilite nephelinites, phonolites and tholeiitic and alkali basalts.
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The Okinawa trough in context of back-arc basins of the world. The (also called ', literally China-Ryukyu Border Trough' ) is a seabed feature of the East China Sea. It is an active, initial back-arc rifting basin which has formed behind the Ryukyu arc-trench system in the West Pacific. It developed where the Philippine Sea Plate is subducting under the Eurasia Plate.
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Certain fits between continents, particularly that between South America and Africa, were known long before the development of a theory that could adequately explain them. The reconstruction before Atlantic rifting by Bullard based on a least-squares fitting at the 500 fathom contour still provides the best match to paleomagnetic pole data for the two sides from the middle of Paleozoic to Late Triassic.
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The first stage began in 25 Ma and lasted until 8 Ma, corresponding to the initial rifting of the oceanic plateau. At 8 Ma, extension began along a transform fault, until approximately 3 Ma, when the Terceira Rift axis was initiated.Neves, M. C., Miranda, J. M., & Luis, J. F. (2013). The role of lithospheric processes on the development of linear volcanic ridges in the Azores.
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The hotspot made a dome that covered the Lake Superior area. Voluminous basaltic lava flows erupted from the central axis of the rift, similar to the rifting that formed the Atlantic Ocean. A failed arm extends north into mainland Ontario where it forms a geological formation known as the Nipigon Embayment. This failed arm includes Lake Nipigon, the largest lake entirely within the boundaries of Ontario.
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The first sequence was deposited in the Jurassic during the rifting which caused the initial formation of the basin. This Jurassic formation is called the Girón Formation which consists of siltstones and rhyolitic tuffs. During this period, the basin also experienced granitic plutonism along its western margins. The Jurassic-Cretaceous angular unconformity, separating the first and second sequence, is representative of the post-rift boundary.
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The Tethys, North Atlantic, and Labrador Phases were all followed by periods of tectonic subsidence and post rift thermal subsidence. At the end of the rifting phase, a passive rift margin phase occurred allowing for new depositional areas within the basin. This shows the stratigraphy of the Hebron fault block within the Jeanne d'Arc Basin. The four main reservoirs which are depleted are labeled.
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A record of this rifting event remains as an indelible mark on the landscape called Mississippi Embayment. It is this embayment that ripped the dramatic gap between the southern Appalachians and the Ouachita-Ozark Highlands. Weathering and erosion prevailed, and the mountains began to wear away. By the end of the Mesozoic Era, the Appalachian-Ouachita Mountains had been eroded to an almost flat plain.
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The Isua greenstone belt in southwestern Greenland contains the oldest known rocks on Earth dated at 3.7–3.8 billion years old. The Precambrian basement of Greenland formed an integral part of the Laurentian Shield that is at the core of the North American continent. Greenland was formed in two rifting stages from the main body of North America. The first, during the Cretaceous period, formed Baffin Bay.
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Faulted and tilted layer of traprock strata visible from left to right. The Hanging Hills of Meriden, Connecticut. Bedrock geological map of Metacomet Ridge Bare Mountain of the Holyoke Range, Massachusetts Traprock layer above; sedimentary layer beneath. Defunct quarry, Plainville Connecticut The Metacomet Ridge is the result of continental rifting processes that took place 200 million years ago during the Triassic and Jurassic periods.
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Most of that volume was delivered by the Colorado River during the Pleistocene, which flowed through the present-day Gran Desierto area approximately 120,000 years before present. This Pleistocene delta migrated westward concomitant with strike-slip faulting and rifting associated with the opening of the Salton Trough and the Gulf of California.Sykes, G., The Colorado Delta, Carnegie Institution/American Geographical Society, New York, 193 p., 1937a.
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The volcanic field Taryatu-Chulutu (, "rocks of Tariat") is a volcanic field in Mongolia. It is part of a volcanic area in Central Asia in the Hangai range that may be linked to the rifting of the Lake Baikal Rift. The field itself is located within the valleys of the Chuluut and Suman rivers. Volcanic activity occurred in the Miocene, Pliocene, Pleistocene and Holocene.
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A graben fault system typical of the Viking graben and Central graben During the Triassic period, the Viking and Central Graben volcanic systems were formed. Upward thrusting rifts were formed during the Triassic comprising the taphrogenic stage. The Atlantic rift zone is associated with the North Sea rifts zone. The Triassic saw active crustal stretching via the rifting process, lower sea levels and volcanic activity.
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Dakota Sandstone Mountains continued to rise in the Sevier orogenic belt to the west during the Cretaceous while the roughly north-south trending Western Interior Basin expanded.Graham 2006, p. 31 Rifting in the Gulf of Mexico helped the southern end of the basin to subside, which allowed marine water to advance northward. At the same time, the shoreline advanced inland from the Arctic region.
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The geology of the Norwegian Sea began to form 60 million years ago in the early Cenozoic, as rifting led to the eruption of mafic oceanic crust, separating Scandinavia and Greenland. Together with the North Sea the Norwegian Sea has become highly researched since the 1960s with the discovery of oil and natural gas in thick offshore sediments on top of the Norwegian continental shelf.
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The Mediterranean Sea, particularly during the Messinian salinity crisis, is a prime example. # Rifted boundaries/passive margins – Also known as divergent boundaries, these areas begin as rift basins, where extension is pulling apart the crust. If this rifting allows water to flood the resulting valley, salt deposition can occur. Examples include the Campos Basin, Brazil, Kwanza Basin, West Africa, and the Gulf of Mexico.
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These new flows blanketed the southeastern third of the state. Many of the volcanoes and smaller cinder cones from this period still exist in eastern Oregon. Afterwards, subsequent rifting produced large fault-block mountains throughout the region. The escarpment-type mountains and high-elevation valleys created by these faults produced the basin and range landscape that makes up much of Oregon's high desert country.
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By 110 Ma the Mid-Atlantic Ridge reached south into the Proto-Caribbean and South Atlantic, effectively separating South America from Africa, and continued rifting in the northern end completed the longitudinal extent of the Atlantic. In Panthalassa the Ontong-Java Mega-LIP resulted in the formation of new tectonic plates and in the Indian Ocean the Kerguelen LIP began to push India northward.
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Accessed December 12, 2018. Together, the Voyagers observed the eruption of nine volcanoes on Io, and there is evidence that other eruptions occurred between the two Voyager fly-bys. Jupiter's moon Europa displayed a large number of intersecting linear features in the low-resolution photos from Voyager 1. At first, scientists believed the features might be deep cracks, caused by crustal rifting or tectonic processes.
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Her recent work has considered the geomorphology of the Apennine Mountains in Italy and mainland Greece. Alongside work on geological faults, she has studied subsidence in rift basins, rates of erosion and how sediment is routed across rift basins. She has studied the evaluation of Late Jurassic rifting in the North Sea. She co-leads MultiRift, a Research Council of Norway program that uses surface process modelling.
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They unconformably lie upon Precambrian granitic and gneissic rocks. The sediments that originally comprised the Ocoee Supergroup accumulated in a string of narrow, deep-water basins that stretched along the entire southern- central Appalachian margin from Tennessee, North Carolina, to Georgia. These basins were rift basins formed by the rifting of Rodinia.Hatcher, RD, Jr. (2005) Southern and Central Appalachians, Regional Geology of North America.
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The Aravalli Mountain Range in Rajasthan, India The Aravalli Mountain Range is in the northwestern part of India. The Aravalli Mountain Range is a northeast- southwest trending orogenic belt in the northwest part of India and is part of the Indian Shield that was formed from a series of cratonic collisions.Mishra, D.C.; Kumar, M. Ravi. Proterozoic orogenic belts and rifting of Indian cratons: Geophysical constraints.
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Some deposits were formed during the amalgamation of the North and South China blocks. A rifting-subduction- collision processes in Danfeng suture zone generated VMS deposits (Cu-Pb-Zn) in the arc area and a marginal fault basin. During the opening of Paleo- Qinling oceans in this period, nickel-copper deposits formed with peridotite gabbro bodies and the ores can be found in Luonan.
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The extension that occurred formed a triangle-shaped rift area due to the kinematics of the rifting taking place like the blades of an opening pair of scissors. The three competing models mentioned above describe this rifting and thinning during the Late Mesozoic and vary slightly between different authors. Here, the three models are illustrated as: # The extrusion model where lateral strike slip faults are projected through the South China Sea and lateral displacement caused by the India-Asia collision forces the extension # The Subduction Model which coincides well with evidence on the formation of the Dangerous Grounds where slab pull caused extension as the Proto-South China Sea was subducted beneath NW Borneo # The continental rift basin model where distant processes of slab roll back south of Borneo near Java and Sumatra caused magmatism leading to the crustal extension northwest of Borneo and formation of A-type granites.
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Separation of the North and South American Plates in the Early-Mid Jurassic beginning with the rotation of the Yucatan Block, along with changes in sea level and thermal activity from the active rift, created a shallow marine basin wherein thick Jurassic salts and evaporites could be deposited. These evaporites overlay a thick transitional crust, the local basement rock prior to rifting, and deposition of salts continued over the forming oceanic crust as rifting spread the sea floor throughout the Jurassic. It was during the Jurassic, approximately 140–160 million years ago, that the shape of the Gulf of Mexico as we know it was formed. The unique shape of the Gulf of Mexico, surrounded on all sides by continental crust, is the result of two different tectonic boundaries: an ocean-continent transform boundary, and a magmatic plume fueled seafloor spreading center active contemporaneously in regards to geologic time.
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The geological history of the Labrador Trough spans several tens of millions of years ranging from around 2.2 Ga to 1.74 Ga: # Following rifting along the Archean margin of the Superior craton about 2.2 billion years ago, rocks of the western part of the Labrador Trough were deposited. This period corresponds to the onset of first- cycle sedimentation and is characterized by the deposition of immature sediments, slightly alkaline volcanics, and the intrusion of mafic dykes. # Deposition of passive margin sediments, MORB-like mafic volcanism and intrusion of mafic sills characterize most of the first cycle between approximately 2.17 and 2.14 Ga. The end of the cycle (<2.06 Ga) is marked by the deposition of dolomite and chert on a restored platform. # Second-cycle platform and basin sedimentation occurred from 1.88 to 1.87 Ga and is associated with a new rifting episode or development of a fore-trough basin.
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Afar triangle in East Africa, an example of an RRR junction and the only triple junction on Earth that can be seen above sea level. An RRR junction is always stable using these definitions and therefore very common on Earth, though in a geological sense ridge spreading is usually discontinued in one direction leaving failed rift zone. There are many examples of these present both now and in the geological past such as the South Atlantic opening with ridges spreading North and South to form the Mid-Atlantic Ridge, and an associated aulacogen in the Niger Delta region of Africa. RRR junctions are also common as rifting along three fractures at 120° is the best way to relieve stresses from uplift at the surface of a sphere; on Earth, stresses similar to these are believed to be caused by the mantle hotspots thought to initiate rifting in continents.
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These are high grade metamorphics, but granitic intrusions are also frequent. In the Neoproterozoic Damara Orogen and Gariep Belt, mineralisation is associated with successive phases of intracontinental rifting (copper, graphite), spreading and the formation of passive continental margins.MME, 2011, p.1 The overlying rocks of the Nama Group in central southern Namibia consist of marine sediments indicating a shallow shelf environment, deposited during the Ediacaran and earliest Cambrian.
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Sakai, H. (1989). Rifting of the Gondwanaland and uplifting of the Himalayas recorded in Mesozoic and Tertiary fluvial sediments in the Nepal Himalayas.Sedimentary Facies in the Active Plate Margin, 723–732. Because of the appearance of glacial diamictite and index plant fossils found in the Lower and Upper Gondwanas respectively, it has been proposed that the Lesser Himalaya had been a part of Gondwanaland during the Permian to Cretaceous.
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The spreading of the South China Sea is no longer active. During the Eocene, extension of the Dangerous Grounds began, followed by further extension during the Oligocene. This extension across the South China Sea was in the northwest-southeast direction and caused thinning and rifting. This led to the formation of the South China Sea basin to the northwest of the Mesozoic arc that once extended across much of SE Asia.
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The Cerro Totora Formation with a thickness of 340 m contains red marine sandstone and siltstone at the lower section. At upper section, the red evaporites are interbedded with carbonate sandstone and siltstone. At the top of the formation, quartz arenites present indicate the upper boundary of the Cerro Totora Formation. The evaporites and red sedimentary rock indicate the transition from syn-rift development to the ending of rifting.
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Paleogeographic situation in the Western Carpathian realm during the Upper Jurassic. Reconstruction of the older phases of development is not possible because of absence of pre-triassic rocks. The development of Pieniny Klippen Belt started on passive margin of European platform in Lower Jurassic with rifting and tectonic subsidence of Oravic unit.Aubrecht, R., Sýkora, M., 2004: Jurassic-Cretaceous Evolution of the Czorsztyn Unit (Pieniny Klippen Belt, Western Carpathians): New Aspects.
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The Late Jurassic basins offshore were infilled and onlapped by the Cretaceous post-rift sequence. These are dominated by mudstones although the Upper Cretaceous sequence from the Viking Graben and south is dominated by chalk. In the outer parts of the Vøring margin rifting restarted in the late Cretaceous, continuing through to the early Palaeocene. This event is interpreted to be a precursor to the break-up of the North Atlantic.
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This connection was broken by rifting and sea-floor spreading 130–110 million years ago. Afterwards, the transoceanic assemblages would have continued to evolve separately, contributing to small differences between taxa. Machado stated that Cajual Island was still attached to the African continent during the Cenomanian. Similarly, Medeiros and colleagues noted that the presence of an island chain or other lasting land connection during that time could explain the faunal similarities.
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5673 (2004): 999-1002. Located southeast of the Sigsbee Knolls, the Campeche Knolls are bounded by Campeche Bank to the East, the Bay of Campeche to the South, and the salt-free abyssal plain called the Veracruz Tongue to the West. Salt deposition is inferred to have occurred in the Late Jurassic, during the rifting stage of the gulf, equivalent to the Louann Salt of the Texas-Louisiana slope.
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The Nam Con Son Basin was developed during the Tertiary by complex rifting of a poorly known basement. The geological formation of Nam Con Son Basin can be separated into two major structural elements: A Pre-Cenozoic strata basement and a Cenozoic sedimented cover. The heterogeneous basement is composed of quartz diorite, granodiorite and Mesozoic metamorphic rocks. While the Pre-Tertiary basement shows an assemblage of volcanic, igneous and metasedimentary rocks.
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Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels worldwide. To the north of Africa the Tethys Sea continued to narrow. Broad shallow seas advanced across central North America (the Western Interior Seaway) and Europe, then receded late in the period, leaving thick marine deposits sandwiched between coal beds. At the peak of the Cretaceous transgression, one-third of Earth's present land area was submerged.
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The Australian Plate is a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately when India broke away and began moving north. Australia and Antarctica began rifting and completely separated roughly . The Australian plate later fused with the adjacent Indian Plate beneath the Indian Ocean to form a single Indo- Australian Plate.
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The Ospwagan Group is younger than and the 1,864 million-year-old Winnipegosis komatiite belt lies to the southwest. Numerous tectonic settings have been suggested for triggering magmatism in the Fox River Belt, including a marginal basin rifting event. At the southern portion of the Circum-Superior Belt, a group of fragmental sediments composed of iron formation was formed during a period of magmatic activity in the Marquette Range Supergroup.
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The Taranaki Basin is an onshore-offshore Cretaceous rift basin on the West Coast of New Zealand. Development of rifting was the result of extensional stresses during the breakup of Gondwanaland. The basin later underwent fore- arc and intra-arc basin development, due to the subduction of the Pacific Plate under the Australian Plate at the Hikurangi Subduction System. The basin covers approximately 100,000 km2 of which the majority is offshore.
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The Hebron Oil field formed as result of the early Mesozoic break up Pangea. Prior to break up the northern part of Africa was connected to what is now Newfoundland. At the break up a passive rift margin formed due to the creation of the Atlantic Ocean. Three major phases of Mesozoic Rifting phases occurred that affected the formation of the Hebron Oil field and Jeanne d'Arc Basin.
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This period begins with the Mesozoic break up of Pangea and the beginning of the basin formation in the Grand Banks of Newfoundland. In the Late Triassic sediments begin to be deposited in what is now the Jeanne d'Arc Basin during a series of Mesozoic rifting events. During the lower Jurassic period, a marine environment existed in the area allowing for the deposition of interbedded carbonates and evaporates.
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During the late Cretaceous major faulting occurred due to the continued rifting of the Atlantic Ocean at the Newfoundland Transform Fault Zone. The lower reservoirs, Hibernia and Jeanne d'Arc formations, are trapped along the up dips of Anticlines and faulted tilted blocks. The main reservoir, the Ben Nevis, is trapped due to a stratagraphic trap occurring above the sandstone and trapped on the sides due to the Egret Fault.
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The magmatically-starved Bonin arc segment has no back-arc basin, inter-arc rift, or rear-arc cross chains. The Mariana segment is characterized by an actively spreading back arc basin known as the Mariana Trough. The Mariana Trough shows marked variations along strike, with seafloor spreading south of 19°15’ and rifting farther north. The IBM arc system southwest of Guam is markedly different from the region to the north.
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Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels worldwide. To the north of Africa the Tethys Sea continued to narrow. Broad shallow seas advanced across central North America (the Western Interior Seaway) and Europe, then receded late in the period, leaving thick marine deposits sandwiched between coal beds. At the peak of the Cretaceous transgression, one-third of Earth's present land area was submerged.
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Approximately 220 million years ago, during the late Triassic period, the supercontinent Pangaea began to break apart. The focus of the rifting began somewhere between where present-day eastern North America and north-western Africa were joined. As the rift began to separate from mainland North America, volcanic activity occurred, forming volcanoes and flood basalts. These flood basalts poured out over the landscape, covering much of southern Nova Scotia.
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It is an unusual hydrothermal site, with its off- axis location and relatively long-lived activity. The source of the hydrothermal fluid that fuels Magic Mountain probably rises along fault systems associated with a recent episode of rifting that, in turn, followed a massive outpouring of lava. These vents are forming seafloor massive sulfide deposits on the ocean floor. Many strange deep-water creatures have been found here.
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Volcanism and a rift system developed in the central North Sea area where basaltic lavas were extruded. The mantle warped upwards creating a dome in the middle of the North Sea where the Iapetus Suture intersected the Tornquist-Teisseyre fault system. The dome area was amidst the Viking Graben, Central Graben and Moray Firth Basin. The Scotland rifting and the extrusive centre of the Forties were associated with the uplifted area.
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In the early Palaeogene period (Caenozoic Era) between 63 and 52 Ma, the North Sea formed, and Britain was uplifted. Some of this uplift was along old lines of weakness from the Caledonian and Variscan Orogenies long before. The post rift phase followed late Jurassic rift events during the late Mesozoic and Cenozoic thermal subsidence. As the rifting stopped, then regional subsidence occurred creating an intracratonic sedimentary basin.
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Continental plates converged and folded up the ocean to form West Junggar residue sea. 5. Rifting occurred again to form Junggar Ocean (JO) (in pink) and Kelamaili Ocean (KO) (in brown), which showed separation from Bogda arc (BA), Kalameili arc (KA) and Altai Arc (AA). 6. JO subducted over KA while KO subducted over AA. 7. Junggar ocean crust subducted over the combined Kelamaili-Altai arc and showed slab rollback. 8.
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Junggar Ocean and Kulumudi Ocean were produced from the third rifting event during lower-mid Devonian. Eventually, the Junggar ocean and Kulumudi Ocean moved towards the north and undergone the subduction from upper Devonian to Late-Carboniferous. At the same time, several volcanic arcs were developed during subduction. Three plates (Tarim, Kazakhstan, and Siberian) converged together to form a trapped ocean that surrounded volcanic arc and orogens in Mid-Carboniferous.
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They are the Qinling-Dabie Orogen in the north and the Song Ma suture in the south. The current configuration of continental blocks is the result of an array of rifting and collision events over more than 400 million years. Simply put, the geological evolution of Southeast Asia is characterized by the Gondwana dispersion and Asian accretion. The Southeast Asia continental blocks successively rifted apart from the Gondwana.
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Based on inspection of extreme metamorphism and post-subduction magmatism at convergent plate margins, paired metamorphic belts are further extended to two contrasting metamorphic facies series: one is blueschist to eclogite facies series that was produced by subducting metamorphism at low thermal gradients of <10 °C/km, and the other is amphibolite to granulite facies series that was produced by rifting metamorphism at high thermal gradients of >30 °C/km.
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Drainage of the Colorado Plateau was significantly altered by the opening of the Gulf of California. Rifting tore Baja California Peninsula northwestward from the Mexican mainland starting some 10 to 5 mya. The ancestral Colorado River responded to the regional downwarping by taking a shortcut to the sea by flowing into the new gulf. This significantly decreased the distance from the river's headwaters and its delta at the sea.
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This event was followed by low-angle extensional faulting along the East Antarctic plate. No uplift occurred during this initial phase of faulting due to counteracting erosional events. Shortly after, during the Mid Cretaceous (100 Ma), the West Antarctic Rift System began to form. Certain models show that the rapid rifting and intense thermal forces are due to a shallow (50 km depth) lithosphere-asthenosphere boundary under the Transantarctic Mountains.
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Trimountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Trimountain.
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Beacon Hill, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The hill formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs of Beacon Hill.
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Eastern Laurussia was still divided from Gondwana by the Paleotethys Ocean. In the Triassic Period of the Mesozoic Era, animals could move without oceanic impediment from Siberia over the North Pole to Antarctica over the South Pole. In the Mesozoic Era, rifting and subsequent opening of the Atlantic split Pangaea. As a consequence, the Variscan Belt around the then periphery of Baltica ended up many hundreds of miles from the Appalachians.
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There is a progression of tectonic regimes that accompany the supercontinent cycle: During break-up of the supercontinent, rifting environments dominate. This is followed by passive margin environments, while seafloor spreading continues and the oceans grow. This in turn is followed by the development of collisional environments that become increasingly important with time. First collisions are between continents and island arcs, but lead ultimately to continent-continent collisions.
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USGS cross-section of the Newark Basin. The Palisades sill is shown intruded into the second layer ( Lockatong formation ) above west dipping precambrian basement ( orange colored ) blocks. Columnar jointing in the Palisades Sill The end of the Triassic Period saw large-scale rifting during the break-up of Pangaea. What is now eastern North America began to separate from what is now north-western Africa, creating the young Atlantic Ocean.
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The extension axis for the Mariana Trough can be subdivided along strike into a southern two-thirds characterized by slow seafloor spreading and a northern third characterized by rifting. From as far north as 19°45'N south to 13°10’N, the spreading ridge has the typical morphology of a slow-spreading ridge, with an axial graben that is sometimes occupied by a central ridge where volcanic activity is concentrated (neovolcanic zone); south of this the ridge more resembles a fast-spreading ridge, probably because magma supply is enhanced by proximity to the arc . Spreading half-rates in the region between 16° and 18°N are estimated at 1.5 to 2.2 cm/year . The ridge becomes punctiform north of 18°30', and true seafloor spreading does not occur north of 19°45'N (but see the different conclusion of ). Rifting forms a series of amagmatic deeps between 19°45'N and 21°10'N called the 'Central Graben' .
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Extension within the basin was determined to be greater than 48% at any given place based on uniform pure shear models and was mostly limited to before 25 Ma. Some extension (3-8%) also occurred after the main rifting phase, coinciding with more rapid sedimentation around 12 Ma. The presence of magmatism in the PRMB dating as recently as the Late Cretaceous-Early Paleocene indicates that the 80 My necessary to reach equilibrium in a plate following a tectonic or magmatic event had not yet been reached when rifting began in the basin. This timing implies that the lithosphere was hotter and weaker than equilibrium during the opening of the South China Sea and the formation of the PRMB. Forward modeling of the PRMB used elastic thickness (Te) values of 1–3 km to more closely reproduce basin geometries. Te values above 3 km could not produce basin geometries close enough to those observed.
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One possibility is they dispersed through vicariance, whereby therizinosaurs were present in the areas that became Asia and North America before the rifting that divided these areas in the Late Triassic. The other possibility is that basal therizinosaurs dispersed between Asia and North America via Europe after the rifting event but before the middle Barremian; between 132–138 million years ago, a temporary land bridge connected North America and Europe, whereafter the landmasses were again isolated from each other, explaining why the basal therizinosaurs Beipiaosaurus from Asia and Falcarius from North America were so morphologically divergent from each other, though coeval. The presence of the derived therizinosaurid Nothronychus, which was most-closely related to Asian genera, in North America during the Turonian stage of the early Late Cretaceous also shows there would have been a faunal interchange between North America and Asia via a late-Early Cretaceous land bridge before that (during the Aptian/Albian), which is also seen in some other dinosaur groups.
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The challenge is met by a group of dwarves, among the last survivors of a genocidal war by Dímon's father. They present Dímon with a chest made from spiders' silk through which time cannot penetrate. Hrafntinna is put inside and is only allowed out occasionally, staying the same age as others age around her. Animation of the historical rifting of Pangaea Decapitating the dwarves, Dímon accidentally cuts Pangea in two, losing half his kingdom.
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Basaltic cones which erupted 600,000 years ago on the caldera's flanks despite their location are not part of the La Reforma volcano; like Isla Tortuga and Tres Virgenes, they are controlled by the tectonic processes that accompanied the rifting of the Sea of Cortez. Also, rivers deposited sediments inside the caldera itself. Seismic activity still occurs at Tres Virgenes volcano. La Reforma could still experience large scale explosive volcanism, especially in its southwestern part.
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The magma that formed the batholith's plutons is thought to have originated from the partial melting of hydrated basaltic rocks at the base of the crust during rifting (extension). Subsequently, the rift basin was inverted. During the ascent the magma followed vertical pathways but emplacement was mostly in the form of tabular bodies. Plutons of the batholith intrude both the deformed strata of Marañón fold and thrust belt and the Casma Group.
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2011 The formation is thought to be separated from the underlying lower Vadito Group by a significant unconformity. It is overlain by the Ortega Formation. Based on uranium-lead dating of zircons, the age of the formation is 1.693 Mya, and it is interpreted as metamorphosed rhyolites from the waning stage of back arc rifting associated with the Yavapai orogeny. It likely correlates with the Burned Mountain Formation in the Tusas Mountains.
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Manitook Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Manitook Mountain.
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Long Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the steep ridge and talus slopes of Long Mountain.
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Well-bedded Torridonian sandstone The Torridonian is a sequence of Neoproterozoic sediments, mainly sandstones that rest unconformably on an old land surface, with up to 300 m of relief locally. The Torridonian is divided into the older Stoer Group and the younger Sleat and Torridon Groups separated by an angular unconformity. Paleomagnetic data suggest that this unconformity represents a major time break. These sediments are interpreted to have been deposited during a period of rifting.
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An episode of hotspot gabbro magmatism occurred at the eastern edge of the Wyoming craton, south of current-day Sudbury. Continental rifting is exhibited by emplacement of mafic igneous rocks on each side of the rift margins. By the Superior and Wyoming provinces had completely separated. From about 2,100 to 1,865 million years ago the Wyoming craton drifted in a westward direction until it docked with the Superior province, northwest of its original position.
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This type of configuration need have existed for only a few million years to have generated the of opening in the rift. Alternatively, the Haida Gwaii block may have been only partially coupled to the offshore plate during a longer period of oblique convergence. Bathyal sediments, perhaps as young as 15 million years, were deposited within the rift zone during and after the rifting took place as the Anahim hotspot passed by.
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Non-volcanic passive margins (NVPM) constitute one end member of the transitional crustal types that lie beneath passive continental margins; the other end member being volcanic passive margins (VPM). Transitional crust welds continental crust to oceanic crust along the lines of continental break- up. Both VPM and NVPM form during rifting, when a continent rifts to form a new ocean basin. NVPM are different from VPM because of a lack of volcanism.
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500px NVPM are the result of rifting when a continent breaks up to form an ocean, producing transitional crust without volcanism. Extension causes a number of events to occur. First is lithospheric thinning, which allows asthenospheric upwelling; heating further erodes the lithosphere, furthering the thinning process. The extensional forces also cause listric faults and continentward dipping reflectors that help identify NVPM and distinguish them from VPM, characterized by seaward-dipping seismic reflectors.
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Ragged Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Ragged Mountain.
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Precambrian Environment in Hainan Island The Shilu Group was composed of siliciclastic and carbonate sedimentary rocks from shallow oceanic rifting environment with low grade metamorphism. Conformably lying above the Shilu Group was the Shihuiding Formation which was generally low-grade, siliciclastic rocks deposited in foreland basin. The sedimentation took place in the period between Late Mesoproterozoic and Early Neoproterozoic. The rocks were then regionally metamorphosed in the late South China Jinningian event.
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There are several theories as to how a greenhouse Earth can come about. The geological record shows CO2 and other greenhouse gases are abundant during this time. Tectonic movements were extremely active during the more well-known greenhouse ages (such as 368 million years ago in the Paleozoic Era). Because of continental rifting (continental plates moving away from each other) volcanic activity became more prominent, producing more CO2 and heating up the Earth's atmosphere.
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Peter's Rock, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Peter's Rock.
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Sverdrup Basin is a Carboniferous rift basin in the Queen Elizabeth Islands that formed during the Boreal Rifting Episode. It has a northeast-southwest axis of about and a width of up to , encompassing an area of . Baffin Basin is a north-northwest trending geologic structure underlying much of central Baffin Bay. It formed as a result of seafloor spreading during the Tertiary opening of Baffin Bay around 56 million years ago.
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Normal faults, including the Manaia Fault, formed as the Taranaki Basin developed during seafloor spreading. Rifting continued until the Eocene (~56 Ma), when the Taranaki Basin underwent passive subsidence. Kapuni collected abundant organic material under coastal plain and fluvio-estuarine environments during much of the Eocene. A broad marine transgression occurred in the Late Oligocene to Early Miocene (~28-20 Ma), and mudstones were deposited on top of the Eocene organic-rich shales and sandstones.
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The Labrador phase occurred from the middle to late Cretaceous. This rifting phase began with northwest to southwest trending faults fragmenting the basin. One of the major faults formed was the Trans Basin Fault Zone which formed some of the traps to the adjacent oil fields. The major event happening at the end of this period was the deposition of the Ben Nevis formation which forms the main reservoir for the Hebron Oil Field.
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It is the lowest unit of the Nanxiong Basin, a small graben created during Mesozoic rifting. Buck et al. state that it overlies Jurassic granite basement, and is conformably overlain by the Shanghu Formation. Alternative stratigraphic schemes for the Nanxiong basin have been proposed, one of which refers to the Nanxiong succession as the Nanxiong Group, and dividing it into the Yuanfu, Zhutian and Zhenshui formations, and overlying the Albian to Turonian Changba Formation.
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Rifting began as magma welled up through the weakness in the crust, creating a volcanic rift zone. Volcanic eruptions spewed ash and volcanic debris across the landscape as these severed continent-sized fragments of Pangea diverged. The gash between the spreading continents gradually grew to form a new ocean basin, the Atlantic. The rift zone known as the mid-Atlantic ridge continued to provide the raw volcanic materials for the expanding ocean basin.
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The tectonic of the peninsula started from Oligocene to Early Miocene, followed by deformation from Early Miocene to Middle Miocene that resulted in the opening of Sulu Sea and widening of Sandakan Basin. The rifting stopped in Late Miocene to early Pliocene which caused a major uplift around the Sandakan Peninsula with heavy erosion. The Upper Miocene formation dominates the eastern area of the peninsula with two main lithologies of sandstone and mudstone.
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Mount Nonotuck, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridges of Mount Nonotuck.
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The volcano is part of the McMurdo Volcanic Group, one of the largest provinces of alkaline volcanism in the world. It has been subdivided into four subprovinces; Mount Rittmann is considered part of the Melbourne subprovince or of the Mount Overlord volcanic field. The volcanic province is related to the tectonic events that occurred during the rifting of the Ross Sea. Activity commenced during the Eocene- Oligocene and continued into the Holocene.
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However, they are normally worn away after years of erosion. Many granitoid rocks are located in areas that have experienced crustal thickening during orogenies but others, known as anorogenic granitoids, are unrelated to convergent boundaries or subduction zones. These anorogenic granitoids may represent the deep sources for rift volcanism exposed where erosion has removed the volcanic rocks and other evidence of rifting. These A-type granitoids may have been produced by hotspots or mantle plumes.
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North-south rifting with the breakup of Pangea in the Triassic segmented the Ringkobing-Fyn High into a narrow graben. Sedimentation occurred in fault-bound alluvial fan deposits with occasional small marine transgressions, such as the Muschekalk Sea in the mid- Triassic in the Ringkobing-Fyn High. Triassic outcrops are only found on southern shore of Bornholm. Extensional faulting occurred throughout the Mesozoic, but overall, conditions remained the same into the Cretaceous.
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Mount Holyoke, like much of the Metacomet Ridge, is composed of basalt, also called trap rock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the dramatic cliffs and ridges of Mount Holyoke.
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As the Laramide Orogeny ended around 48 million years ago, the accretion of the Siletzia terrane began in the Pacific Northwest. This began the volcanic activity in the Cascadia subduction zone, forming the modern Cascade Range, and lasted into the Miocene. As extension in the Basin and Range Province slowed by a change in North American Plate movement circa 7 to 8 Million years ago, rifting began on the Gulf of California.
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Much of the coastal topography around the bay is very steep, rising almost immediately from the shoreline to elevations of . Like the other major channels of the Bras d'Or Lake (St. Patricks, Great Bras d’Or, Little Bras d’Or and St. Andrews), East Bay has a northeast – southwest orientation. Rifting and regional tectonic plate movements some 360 million years ago formed this directional series of small fault bounded basins between highlands of resistant crystalline rock.
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East Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of East Mountain.
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Mount Norwottock, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the dramatic cliffs and ridges of Mount Norwottuck.
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Provin Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Provin Mountain.
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The basalt ridges are the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa. These basalt floods of lava happened over a period of 20 million years. Bedrock geology. Purple = basalt; surrounding brown & blue- grey = sedimentary rock Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows, which eventually lithified into sedimentary rock.
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West Suffield Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of West Suffield Mountain.
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Terrigenous volcanic rocks which may have originated from rifting are located in the South Urals, metamorphosed to greenschist grade, with amphibolites in linear folds. Dolomite limestones with stromatalite fossils and quartzites are found in the Kazakh Uplands. Low-grade metamorphism and granitization took place from 1.2 billion to one billion years ago. All the Precambrian massifs hold Upper Riphean quartzite and quartz sandstone, dated with detritral zircon to 850 million years ago.
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The McMurdo Volcanic Group is a large group of Cenozoic volcanic rocks in the western Ross Sea and central Transantarctic Mountains areas of Antarctica. It is one of the largest provinces of alkaline volcanism in the world, having formed as a result of continental rifting along the West Antarctic Rift System. The McMurdo Volcanic Group is part of the Western Ross Supergroup, a stratigraphic unit that also includes the Meander Intrusive Group.
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Xinjiang paleocraton was pulled apart for a continental rifting episode to form extensional basins in Late Cambrian. The continuous divergence of the continental crust during late Cambrian to Ordovician shaped the West Junggar Ocean. The West Junggar Ocean presented as the present Tangbale and Honguleleng ophiolites from intra-plate volcanism, and then this volcanism shut in mid-upper Ordovician. The Ordovician first ocean basin indicated that eastern Junggar was over passive margin.
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The Proto-Caribbean Sea continued to grow and the Paraná- Etendeka LIP began to break Africa into three pieces. The Falkland Plateau broke-up from southern Africa at 132 Ma and Madagascar ceased to move independently c. 120 Ma. In the Panthalassic Ocean the Pacific Plate continued to grow; the Arctic Alaska-Chukotka terrane formed the Bering Strait. Continued rifting opened new basins in the Indian Ocean, separating India, Antarctica, and Australia.
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Later in the mid-Triassic a similar sea penetrated along the equator from the west. The remaining shores were surrounded by the world-ocean known as Panthalassa ("all the sea"). All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates; thus, very little is known of the Triassic open ocean. The supercontinent Pangaea was rifting during the Triassic—especially late in that period—but had not yet separated.
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The ANS foreland basin was broken down into three depositional and tectonic sequences that define the deposits and structure of the basin. From the Mississippian to Jurassic a carbonate ramp built out to the south on the passive margin of the Arctic Alaskan Plate. The Arctic Alaskan Plate was then rifted and rotated in the Early to Mid Cretaceous. This rifting created the Barrow Arch that separates the ANS from the Canadian Basin.
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Higby Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Higby Mountain.
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Pistapaug Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Pistapaug Mountain.
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The Central Plateau of Iran is divided into two drainage basins. The northern basin is Dasht-e Kavir (Great Salt Desert), and Dasht-e- Lut is the southern basin. In Yemen, elevations exceed 3,700 meters in many areas, and highland areas extend north along the Red Sea coast and north into Lebanon. A fault-zone also exists along the Red Sea, with continental rifting creating trough-like topography with areas located well-below sea level.
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Besek Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Besek Mountain.
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The basement rocks of the continental crust tend to be much older than the oceanic crust. The oceanic crust can be from 0–250 million years in age, and is usually thinner (10 miles or so) and composed of basaltic rocks. Continental crust is older because continental crust is light and thick enough so it is not subducted, while oceanic crust is periodically subducted and replaced at subduction and oceanic rifting areas.
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Peak Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Peak Mountain.
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Hatchett Hill, like much of the Metacomet Ridge, is composed of basalt, also called trap rock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Hatchett Hill.
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Pinnacle Rock, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Pinnacle Rock.
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Basins associated with collision zones and subduction zones are where most of the remaining giant oil fields are found. Passive margins are petroleum storehouses because these are associated with favorable conditions for accumulation and maturation of organic matter. Early continental rifting conditions led to the development of anoxic basins, large sediment and organic flux, and the preservation of organic matter that led to oil and gas deposits. Crude oil will form from these deposits.
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Farmington Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Farmington Mountain.
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Rattlesnake Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Rattlesnake Mountain.
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Short Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Short Mountain.
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The trap is a group of three easterly dipping tilted fault blocks associated with westerly dipping normal faults formed by rifting during the Late Jurassic on the east side of the Viking Graben. The three main fault blocks are known as Alpha, Gamma and Alpha North. The eastern boundary of the Oseberg fault blocks with the Horda Platform is formed by the major Brage fault. The structural dip is an average 6–10 degrees.
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The earliest formation in the known stratigraphic history of the Owambo Basin comprises what is geologically termed the basement and is compositionally zoned with mostly granite and gneiss. There is a metamorphic overprint on the majority of the granite from the tectonic history of rifting and compression, causing mass devolitilization of the basement rock. This section is overlain by a layer of volcanics, a likely accompaniment to the compression involved in the formation of Rodinia.
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Lifted fault-block geology Tilted fault-block formation in the Teton Range Belasitsa, Rila - Rhodope massif, Bulgaria Fault-block mountains often result from rifting, an indicator of extensional tectonics. These can be small or form extensive rift valley systems, such as the East African Rift zone. Death Valley in California is a smaller example. There are two main types of block mountains; uplifted blocks between two faults and tilted blocks mainly controlled by one fault.
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Parallel to geological and geophysical measures (e.g. isotope ratios and seismic velocities) it is constructive to test hypotheses on computer based geodynamical models. A 3D numerical geodynamical model of the plume-crust coupling was capable of reproducing the lateral asymmetry of the EAR around the Tanzania craton. Numerical modeling of plume-induced continental break-up shows two distinct stages, crustal rifting followed by lithospheric breakup, and the upwelling between stages of an upper mantle plume.
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Fowler Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Fowler Mountain.
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Bradley Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Bradley Mountain.
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Lamentation Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Lamentation Mountain.
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Mount Tom, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the dramatic cliffs and ridges of Mount Tom.
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The Pennine Fault System is a NW-SE trending zone of faulting that forms the southwestern boundary to the Pennines in Cumbria. It was formed as a normal fault during Permian rifting, bounding the Vale of Eden basin, which has a half-graben geometry. It links through to the Dent Fault at its southeastern end. Rocks of Ordovician and Silurian age outcrop between the two main strands of the fault, forming the Cross Fell inlier.
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Tigray Escarpment in northern Ethiopia exposing the layers of the Ethiopia- Yemen Continental Flood Basalts. The geology of Ethiopia includes rocks of the Neoproterozoic East African Orogeny, Jurassic marine sediments and Quaternary rift-related volcanism. Events that greatly shaped Ethiopian geology is the assembly and break-up of Gondwana and the present-day rifting of Africa. Rocks formed by the East African Orogeny 880 to 550 million years ago make up the oldest geological units in Ethiopia.
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The environment of deposition for this section is uncertain; however, due to the presence of thin, well-graded layers and a lack of marine fossils, it is possible that the formation was deposited in a closed lacustrine setting. Overlaying the syn-rift sediments are 200 meters of Pliocene to Pleistocene hemipelagic marine sediment with intermittent volcanic glass. This sediment layer is believed to be deposited after the end of rifting due to its subhorizontal seismic reflection profile.
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However, if the velocity of slab rollback and trench retreat exceeds that of the overriding plate, then back-arc extension will occur. The Pliocene-Pleistocene changes in Tyrrhenian back-arc extension may have also been influenced by the adjacent Adriatic and Sicilian forelands. These sectors were not thinned by rifting and are characterized by normal continental lithosphere. During its southeastward migration, the passively retreating oceanic slab had to adjust and deform in relation the large and buoyant continental sectors.
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Sedimentation in the Kutai basin has been relatively constant throughout the Tertiary. Syn-rift deposition in the Eocene was focused in small, local depocenters within individual half-grabens. Lithology of the initial graben fill is highly variable due to the wide zone of rifting, and ranges from fully terrestrial in the western basin, to fully marine in the eastern basin. A typical initial graben fill in the Kutai basin is composed of coarse and poorly sorted basement derived material.
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In fact, Cenozoic sediments cover much of Somaliland. The formation of the Somali Plate began 60 million years ago and accelerated at the end of the Oligocene, approximately 23 million years ago. As the Arabian Plate and Somali Plate rifted apart, forming the Gulf of Aden through sea floor spreading in the Late Miocene magma intruded between the two plates. Of particular significance for Somaliland, rifting in the Oligocene and Miocene reactivated Mesozoic normal faults, forming the Guban Basin.
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Topography of Senegal The geology of Senegal formed beginning more than two billion years ago. The Archean greenschist Birimian rocks common throughout West Africa are the oldest in the country, intruded by Proterozoic granites. Basins formed in the interior during the Paleozoic and filled with sedimentary rocks, including tillite from a glaciation. With the rifting apart of the supercontinent Pangaea in the Mesozoic, the large Senegal Basin filled with thick sequences of marine and terrestrial sediments.
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The extensive Masset Formation on Haida Gwaii has been suggested by some scientists to be a northern extension of the Pemberton Volcanic Belt. However, the geochemistry and physical volcanology of the Masset Formation indicates that it formed in a rifting environment in contrast to other Pemberton Belt features. Extensive erosion of the Pemberton Volcanic Belt has removed most of its volcanic peaks, exposing their magma systems. These form several intrusive bodies such as batholiths and stocks.
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The Orinoco oil belt has many unique features from a geological point of view. All of these unique features are related to the tectonic events that formed the field. The first tectonic event that can be attributed to the formation of the field is when North America separated from Gondwanaland in the Late Triassic/Early Jurassic (~200 million years ago). The rifting in this period is represented by Late Jurassic basalts deposited in the Espino graben.
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Geolines, 17, p. 15-16 During the Middle Jurassic to Lowermost Cretaceous an elevated continental ribbon called the Czorsztyn Ridge evolved due to the thermal uplift and continental break-up at the southern side of the Czorsztyn Ridge. Rifting resulted in the opening of basinal area called the Kysuca basin or Vahic Ocean (South Penninic or Piemont ocean equivalent) to the south of the Oravic area.Plašienka, D., 2002: Early Stages of Tectonic Evolution of the Pieniny Klippen Belt.
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Recent scientific work indicates that the Earth's crust below the Taupo Volcanic Zone may be as little as 16 kilometres thick. A film of magma 50 kilometres (30 mi) wide and 160 kilometres (100 mi) long lies 10 kilometres under the surface. 01311. The geological record indicates that some of the volcanoes in the area erupt infrequently but have large, violent and destructive eruptions when they do. There is also some possible rifting in the Taupo Volcanic Zone.
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Quartz Mountain is one of the westernmost peaks in the Wichita Mountains. In simplest terms, the Wichita Mountains are rocky promontories and rounded hills made of red and black igneous rocks, light-colored sedimentary rocks, and boulder conglomerates. The Wichita Mountains were formed in four distinct geologic episodes. :1. Magmatism induced by continental rifting just prior to and in the Cambrian Period produced the granites and rhyolites (the red rocks), gabbroic rocks, anorthosites, and diabases (the black rocks). :2.
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Shungite has been regarded as an example of abiogenic petroleum formation, but its biological origin has now been confirmed. Non-migrated shungite is found directly stratigraphically above deposits that were formed in a shallow water carbonate shelf to non-marine evaporitic environment. The shungite bearing sequence is thought to have been deposited during active rifting, consistent with the alkaline volcanic rocks that are found within the sequence. The organic-rich sediments were probably deposited in a brackish lagoonal setting.
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The basalt cliffs are the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa. These basalt floods of lava happened over a period of 20 million years. Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows, which eventually lithified into sedimentary rock. The resulting "layer cake" of basalt and sedimentary sheets eventually faulted and tilted upward.
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Haida Gwaii was displaced approximately to the north along a series of faults extending through Sandspit and Louscoone Islet. This period of rifting and crustal extension contributed to the formation of the Queen Charlotte Basin. While the rift was in development, a conservative plate boundary would have extended northwards from the landward end of the rift. Such a plate boundary might have been similar to the Gulf of California – San Andreas fault system in the U.S. state of California.
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The Hanging Hills of Meriden are part of the Metacomet Ridge, which is nearly continuous from Belchertown, Massachusetts to Branford, Connecticut. The hanging Hills were formed by volcanic activity 200 million years ago during the rifting apart of North America from Eurasia. Two major lava flows covered the red sandstone valley in Meriden. Each cooled and hardened into trap rock (also known as basalt) and was gradually covered by sand and mud which eroded from the surrounding hills.
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The formation lies discontinuously on the Espinaso Formation and interfingers with the overlying Blackshare Formation, with the boundary placed at the highest thickly bedded tabular sandstone below the lenticular conglomerate of the Blackshare Formation. The Tanos Formation dips 20 to 32 degrees to the northeast. It is interpreted as sediments deposited in a closed basin during early rifting along the Rio Grande rift, and is the oldest exposed Santa Fe Group formation near the Albuquerque Basin.
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The Great Escarpment formed about 80 million years ago due to scarp retreat from a new continental edge formed by rifting. This was similar to the model in the western rift of East Africa. The Great Divide is an upwarp that lies tens or hundreds of kilometers from the chasmic fault of the continental margin, creating a drainage divide. The sequence of formation appears to have started with erosion of the plain and formation of a river pattern.
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After sufficient thinning of the lithosphere, this serpentinized material is emplaced at the continent- ocean transition. This is why the transitional crust of NVPM are made of serpentinized peridotite instead of magmatic structures seen in VPM. Since the emplacement of the peridotite, oceanic crust has been forming at the Mid- Atlantic Ridge and driving the two NVPM apart. The simple shear detachment became a deactivated detachment fault once this rifting process began the formation of new oceanic crust.
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Shibam-Kawkaban ignimbrite, Yemen, part of the Ethiopia-Yemen CFB The Ethiopia-Yemen Continental Flood Basalts were erupted during the Oligocene. They cover an area of about 600,000 km2 in Yemen and Ethiopia, with an estimated volume of greater than 350,000 km3. They are associated with the Afar Plume and the initiation of rifting in the southern Red Sea and Gulf of Aden. In Ethiopia flood basalts cover an old erosion surface with occasional flat areas or peneplains.
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The basalt ridges are the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa. These basalt floods of lava happened over a period of 20 million years. Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows, which eventually lithified into sedimentary rock. The resulting "layer cake" of basalt and sedimentary sheets eventually faulted and tilted upward.
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The tectonic structure of Iceland is characterized by various seismically and volcanically active centers. Iceland is bordered to the south by the Reykjanes Ridge segment of the Mid-Atlantic Ridge and to the north by the Kolbeinsey Ridge. Rifting in the southern part of Iceland is focused in two main parallel rift zones. The Reykjanes Peninsula Rift in SW Iceland is the landward continuation of the Reykjanes Ridge that connects to the Western Volcanic Zone (WVZ).
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The final phases of mountain building occurred as Laurentia completed its collision with Gondwana and Europe to form the supercontinent Pangea. Beginning around 200 million years ago, rifting broke apart Pangea. Erupting basalt lavas formed the new oceanic crust of the Atlantic Ocean, wedging apart Africa, Europe and North America along the approximate lines where the continents collided. The Connecticut River Valley and the Middleton Basin formed as failed rifts, filling with sediment that preserve dinosaur footprints.
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In the waning stages of the flood basalt episode, large explosive caldera-forming eruptions also occurred. The Ethiopian Highlands were eventually bisected by the Great Rift Valley as the African continental crust pulled apart. This rifting gave rise to large alkaline basalt shield volcanoes beginning about 30–31 million years ago.January 2005: The Ethiopian Large Igneous Province The northern Ethiopian Highlands contain four discernible planation surfaces the oldest one being formed not later than in the Ordovician Period.
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About 300 million years ago, North America merged with Africa, connecting Florida with North America. Volcanic activity centered on the eastern side of Florida covered the prevalent sedimentary rock with igneous rock. Continental rifting began to separate North America from Gondwana about 180 million years ago.Lodge. p. 3. When Florida was part of Africa, it was initially above water, but during the cooler Jurassic Period, the Florida Platform became a shallow marine environment in which sedimentary rocks were deposited.
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The Oslo Graben or Oslo Rift is a graben formed during a geologic rifting event in Permian time, the last phase of the Variscan orogeny. The main graben forming period began in the late Carboniferous, which culminated with rift formation and volcanism, with associated rhomb porphyry lava flows. This activity was followed by uplifting, and ended with intrusions about 65 million years after the onset of the formation. It is located in the area around the Norwegian capital Oslo.
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Local preservation of 3.6–3.0 Ga gneisses and widespread isotopic evidence for crust of this age incorporated into younger plutons indicates that the Wyoming Craton originated as a 100,000 km2 middle Archean craton that was modified by late Archean volcanic magmatism and plate movements and Proterozoic extension and rifting. The Wyoming, Superior and Hearne-Ray cratons were once sections of separate continents, but today they are all welded together. The collisions of these cratons began before ca.
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Where full rifting occurred, the Atlantic Ocean was created. Along these rifts, magmatic activity never stopped, as shown by the ongoing eruption of lava along the Mid-Atlantic Ridge. The basins are characterized by west to northwest dipping strata in the southern rifts (North Carolina to New York), while the northern ones (Connecticut to Nova Scotia) tend to dip northward. Many of the grabens have prominent signs of igneous activity, with diabase intrusions and basalt flows being quite common.
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Paleozoic rocks cover one-third of the territory, northwest of Fury and Hecla Strait, forming part of the Arctic Platform and continuing north to Ellesmere Island. In the southeast, they are continuation of the Hudson Platform beneath the Foxe Basin. Subsidence and craton rifting are recorded in Cambrian strata, with clastic sequences left by a marine transgression. A stable platform developed from the Cambrian through the Silurian and thick carbonates with high oil and gas potential deposited.
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Through the Cretaceous, sedimentation continued in the Sverdrup Basin, producing oil and gas forming conditions and Bent Horn light crude field. Rifting and alkaline volcanism in the Cretaceous began the process of siliclastic deposition in northern Baffin Island and northern Ellesmere Island. Diamond-bearing kimberlite pipes formed on Somerset Island, exposed along the Brodeur Peninsula and northwest Baffin Island. The Jericho diamond pipes are part of a northern continuation of Lac de Gras field in the northern Slave Province.
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The Brandberg Massif or Brandberg Intrusion is a granitic intrusion, which forms a dome-shaped massif. It originated during Early Cretaceous rifting that led to the opening of the South Atlantic Ocean. Argon–argon dating yielded intrusive ages of 132 to 130 Ma. The dominant plutonic rock is a homogeneous medium grained biotite-hornblende granite. In the western interior of the massif (Naib gorge), a 2 km in diameter body of pyroxene-bearing monzonite is exposed.
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In the Mesozoic, rifting in the Triassic began to break apart the supercontinent Pangea which had assembled during the Alleghanian orogeny. Thinning of the crust produced diabase dikes in the early Jurassic 200 million years ago throughout the Piedmont, as well as felsic dikes and diabase sills in the Deep River Basin. Seismic data indicates that large basalt flows found offshore extend onshore, reaching Charleston, South Carolina. Few Cretaceous and Jurassic rocks are rare on the continental margin.
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During rifting from the Late Cretaceous through the Early Oligocene, shallow lacustrine and fluvial to deltaic sediment was deposited in the PRMB. The sandy mudstone of the Shenhu formation was first deposited during the Paleocene and Early Eocene. Gray mudstones make up the Wrenching formation deposited in the Middle Eocene, with coal beds occurring near the top. Alternating layers of lacustrine and sandy mudstones were deposited as the Enping formation during the Late Eocene and Early Oligocene.
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Three types of plate boundaries exist, with a fourth, mixed type, characterized by the way the plates move relative to each other. They are associated with different types of surface phenomena. The different types of plate boundaries are: Divergent boundary Convergent boundary Transform boundary # Divergent boundaries (Constructive) occur where two plates slide apart from each other. At zones of ocean-to-ocean rifting, divergent boundaries form by seafloor spreading, allowing for the formation of new ocean basin.
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After about 725 Ma, deposition continued in a mostly passive margin setting along the western edge of the Palaeo-Pacific Ocean, with renewed rifting during the Ediacaran to the east (present day) of the main depocentres until being terminated by the Delamerian Orogeny. The most abundant rock types indicate a transition from evaporitic depositional environments through to proximal marine, glacial and marine depositional environments. The thickest parts of the stratigraphy reach a total cumulative thickness of about 24,000 m.
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Prior to tectonic rifting, the East Tasman Plateau microcontinent was attached to the southeast of Tasmania and the north east of the South Tasman Rise. To the northeast, east and south east of the plateau was the Lord Howe Rise. In the Cretaceous period, the continental breakup of Gondwana started near Tasmania. About a rift entered the east coast of Tasmania from the south and split off the Lord Howe Rise from the South Tasman Rise to the west.
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It extends a total of in three arms from the Afar Triangle to Mozambique. The connecting three arms form a triple junction. The northernmost branching arm extends North through the Red Sea and into the Dead Sea, while the eastern arm extends through the Gulf of Aden and connects to the Mid-Indian Ocean ridge further to the east. Both of these rifting arms are below sea level and are similar to a mid-ocean ridge.
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The Rivera Transform Fault, also referred to as the Rivera Fracture Zone, is a right lateral-moving (dextral) transform fault which lies along the seafloor of the Pacific Ocean off the west coast of Mexico just south of the mouth of the Gulf of California. It runs between two segments of the East Pacific Rise, forming the southwest boundary of the small Rivera Plate. The fault is broken into two segments, bisected by a short rifting zone.
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Evidence of collision and rifting between continents raises the question as to what exactly were the movements of the Archean cratons composing Proterozoic continents. Paleomagnetic and geochronological dating mechanisms have allowed the deciphering of Precambrian Supereon tectonics. It is known that tectonic processes of the Proterozoic Eon resemble greatly the evidence of tectonic activity, such as orogenic belts or ophiolite complexes, we see today. Hence, most geologists would conclude that the Earth was active at that time.
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This orogenic crest is today buried beneath the Dallas–Waco—Austin–San Antonio trend. The late Paleozoic mountains collapsed as rifting in the Jurassic period began to open the Gulf of Mexico. Pangea began to break up in the Triassic, but seafloor spreading to form the Gulf of Mexico occurred only in the mid- and late Jurassic. The shoreline shifted again to the eastern margin of the state and the Gulf of Mexico's passive margin began to form.
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Meyer 1983 The formation is interpreted as deposition of fanglomerates (mostly derived from the Datil-Mogollon volcanic field to the southwest) and playa sediments in a closed basin in the early stages of rifting along the Rio Grande rift. It is thus typical of the lower Santa Fe Group. The formation was severely deformed in the late Miocene or early Pliocene and some beds dip as much as 60 degrees. Faults displace the formation hundreds to thousands of meters.
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Trenches: These are the deepest features of ocean basins; the deepest being the Mariana trench (~36,000 feet). They are formed by flexing of the oceanic lithosphere, developing on the ocean side of island arcs. Back-arc basin: They are also referred to as marginal seas and are formed in the inner, concave side of island arcs bounded by back-arc ridges. They develop in response to tensional tectonics due to rifting of an existing island arc.
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Subsistence related to this caused deep deposits of sediments on the east and some sediment remnants in pop downs in central parts of Spain. Two stages of rifting occurred in the east, one from Later Permian to Triassic, and the second from Late Jurassic to early Cretaceous. On the south side deposits of carbonates and clastic sediments formed a shelf in shallow water during late Triassic and Liassic times. This was rifted in Toarcian times (Early Jurassic 190 Ma).
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The thrust front is visible as the Thaumasia Highlands. Unlike on Earth, where the rifting of plates produces a corresponding subduction zone, the thick lithosphere of Mars is unable to descend into the mantle. Instead, the compressed zone is scrunched up and sheared laterally into mountain ranges, in a process called obduction. To complete the analogy, the huge Olympus Mons and the Tharsis Montes are merely summit cones or parasitic cones on a much larger volcanic edifice.
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Satellite images of Mars have shown that the Thaumasia Plateau has large amounts of thrust faults, normal faults, and ridges. This rifting has resulted in canyons, and compression at the front of the "mega-slide" has caused the ridges and thrust faults observed at low end of the region. To explain these faults and ridges, a four-stage model involving gravity spreading is used: # A thick salt layer is deposited. This is possible in either wet or dry conditions.
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Red-shouldered hawk Saltonstall Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Saltonstall Mountain.
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Portion of North Africa that rifted to form Greater Adria The continent formed by rifting from the north Africa portion of the supercontinent of Gondwanaland 240 million years ago. It broke free into the Neo-Tethys Ocean and headed towards Laurasia. About 200 million years ago, the microcontinent of Iberia separated from the bulk of Greater Adria. The continent ended up accreting to the south Europe portion of the supercontinent of Laurasia, 140 million years ago.
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Verona Rupes, right of center, photographed by the unmanned Voyager 2 spaceprobe in January 1986. Verona Rupes is a cliff on Miranda, a moon of Uranus. The cliff face, previously thought to be from high, as of 2016 is estimated to be high, which makes it the tallest known cliff in the Solar System. It may have been created by a major impact, which caused the moon to disrupt and reassemble, or by the crust rifting.
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Animation of the rifting of Pangaea From 320 Ma onward, Gondwana, Laurussia, and intervening terranes merged to form the supercontinent Pangea. Pangea's main amalgamation occurred during the Carboniferous but continents continued to be added and rifted away in the Late Paleozoic to Early Mesozoic. Pangea ruptured during the Jurassic, preceded by and associated with widespread magmatic activity, including the Karoo flood basalts and related dyke swarms in South Africa and the Ferrar Province in East Antarctica.
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In particular, the rifting event initiated the opening of the Tethys Ocean during which the Cimmerian Plate travelled north and moved away from Gondwana. The boundary and age between the several sub- units are poorly constrained, yet the whole sequence is generally considered to have first developed in Neoproterozoic. The 1840 Ma of the rocks was determined by rubidium–strontium dating of the Baragoan gneiss, however some have allocated the gneiss into the Lesser Himalayan Sequence instead.
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For example, copper and lead deposited in sedimentary rocks indicated rifting and therefore fragmentation of a continent; copper, volcanogenic massive sulfide ore deposits (VMS ore deposits) and orogenic gold deposits indicated subduction and convergent tectonics, meaning amalgamation of continents. Therefore, the formation of a certain type of ore is restricted to a specific period and the minerals are formed in relation with tectonic events. Below the ore deposits are explained based on the period they were formed.
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The Mount Rogers area contains a unique record of the geohistory of Virginia. There is evidence from the rocks that volcanoes were part of the landscape. Roughly 750 million years ago, rift-related (divergent) volcanoes erupted along the axis of what later became the Appalachians, and one remnant of that volcanic zone, with its volcanic rocks, still can be seen at Mount Rogers. Massive rhyolite lava flows erupted at the mountain during the Precambrian rifting event.
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The Jurassic period is divided into three epochs: Early, Middle, and Late. Similarly, in stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, and Upper Jurassic series of rock formations. The Jurassic is named after the Jura Mountains in the European Alps, where limestone strata from the period were first identified. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, and Gondwana to the south.
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Paleomagnetic studies show Kenorland was in generally low latitudes until tectonic magma-plume rifting began to occur between 2.48 Ga and 2.45 Ga. At 2.45 Ga the Baltic Shield was over the equator and was joined to Laurentia (the Canadian Shield) and both the Kola and Karelia cratons. The protracted breakup of Kenorland during the Late Neoarchaean and early Paleoproterozoic Era 2.48 to 2.10 Gya, during the Siderian and Rhyacian periods, is manifested by mafic dikes and sedimentary rift-basins and rift-margins on many continents. On early Earth, this type of bimodal deep mantle plume rifting was common in Archaean and Neoarchaean crust and continent formation. Map of Kenorland breaking up 2.3 billion years ago The geological time period surrounding the breakup of Kenorland is thought by many geologists to be the beginning of the transition point from the deep- mantle-plume method of continent formation in the Hadean to Early Archean (before the final formation of the Earth's inner core) to the subsequent two- layer core-mantle plate tectonics convection theory.
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These two rock fractures, known as the Tintina and Denali fault systems, have been tectonically active since the Cretaceous period as strike-slip faults. The Denali fault to the west and the Tintina fault to the east are nearly long, extending from northern British Columbia to central Alaska. Other mechanisms suggested for triggering volcanism in the Northern Cordilleran Volcanic Province include mantle plumes, deglaciation and slab windows, although continental rifting is the most accurate mechanism for activating volcanism in the volcanic zone. Further evidence for continental rifting in the Northern Cordilleran Volcanic Province is magmas are mainly alkaline, it includes highly alkaline and peralkaline rock types, the main spatial-temporal pattern of volcanism is in the middle of the volcanic province followed by movement to the south, north and possibly northeast, heat flow in the Northern Cordilleran Volcanic Province is high, seismic activity is largely absent in the volcanic province and the largest period of volcanism correlates with an interval of net extension between the Pacific and North American plates.
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In the first stage of rifting, it began to open in the west, then later the eastern section began to open. The two continents pivoted slightly at a point in the west, which squeezed the sediments at the western end of the break against the Yilgarn block, which forced the sediments up to form the range. The sedimentary rocks that were folded up are 1.2 billion years old. The rocks on the range are mostly sedimentary such as sandstone, quartzite, slate and shale.
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Ann G. Harris, et al., The Geology of National Parks,(Dubuque, Iowa: Kendall-Hunt, 2004) Olivine basalts were extruded from a N. 70° E. trending rift zone, oriented along the current Afono and Masefay bays of Tutuila, in the Pliocene or earliest Pleistocene. The Masefau dike complex and talus breccias are remnants of this rifting. Development of the Taputapu, Pago, Alofau, and Olomoana shield domes followed long parallel fissures followed, but when the Pago and Alofau summits collapsed, calderas were formed.
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There is no evidence of rifting until the formation of Rodinia, 1.25 Gya in North Laurentia, and 1 Gya in East Baltica and South Siberia. However, breakup did not occur until 0.75 Gya, marking the end of the Boring Billion. This tectonic stasis may have been related in ocean and atmospheric chemistry. It is possible the asthenosphere—the molten layer of Earth's mantle that tectonic plates essentially float and move around upon—was too hot to sustain modern plate tectonics at this time.
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This rifting continues through the early Cretaceous, and in the middle Cretaceous, begins to assist in the separation of Gondwana (In is what now southern Australia). During this same time, ocean crust is created to the west of Tasmania, and the separation of the Australian Plate from New Zealand, the Antarctic Plate, and the Campbell Plateau occurs.Mehin, K., and Bock, M. P., 1998, Cretaceous source rocks of the onshore Gippsland Basin Victoria; Victoria Initiative for Minerals and Petroleum Report 54, 98 p.
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The initial rifting of Australia and Antarctica in the Jurassic continued through the Cretaceous, with offshore development of a mid ocean ridge seafloor spreading centre. Tasmania was rifted off during this stage. Cretaceous volcanism in the offshore of Queensland was related to a minor episode of arc formation, typified by the Whitsunday Islands, followed by development of offshore coral platforms, passive margin basins and far-field volcanism throughout the quiet Hunter- Bowen orogenic belt. Cretaceous sedimentation continued in the Surat Basin.
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North Sea Central Graben North Sea Viking Graben Rocks of Jurassic age are exposed onshore at one locality on Andøya and have been discovered nearshore and beneath one fjord (Beitstadsfjord) northeast of Trondheim. As with the Triassic, Jurassic strata have a wide distribution along the whole continental shelf. They were dominantly deposited in a deltaic to shallow marine environment. The Late Jurassic was the main rifting phase in the Central Graben, Viking Graben, More Basin, Vøring Basin and on the Barents shelf.
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By , the Wyoming craton is thought to have completely separated from the southern Superior province, this is consistent with the occurrence of a 2,076- to 2,067-million-year-old hotspot centered just south of the Superior province and east of the MRV. The 2,125- to 2,101-million-year-old Marathon and 2,077- to 2,076-million-year-old Fort Frances dikes, both on the present-day Superior province north of the Great Lakes tectonic zone, are consistent with rifting during this time period.
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Paleomagnetic studies additionally show an anticlockwise 35° rotation of Iberia. The drifting motion of Iberia had taken up the entire Lower Cretaceous. Due to the rotational motion, the northeastern edge of Iberia started to interfere with Aquitania, first creating transtensional pull-aparts along the North Pyrenean Zone in the Middle Albian. The crustal thinning associated with the transtensional rifting process led to HT/LP metamorphism in the North Pyrenean Zone, its onset being dated at about 108 million years ago.
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This includes slab windows, mantle plumes, crustal extension and deglaciation. The most common and best mechanism used to explain NCVP volcanic activity is incipient rifting of the North American Plate caused by crustal extension. As the continental crust stretches, the near surface rocks fracture along steeply dipping cracks parallel to the rift known as faults. Mafic magma rises along these fractures to create fluid lava flows, although more viscous felsic magma also makes its way to the surface and can produce explosive eruptions.
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All of the fragments that make up the Armorican terrane are thought to have originally formed part of the northern margin of Gondwana. Rifting initiated in the Cambrian to Ordovician although the terrane was still close enough to Gondwana to be affected by the Andean- Saharan glaciation during the late Ordovician. Complete separation from Gondwana, across the developing Paleotethys Ocean, is thought to have occurred towards the end of the Silurian. At this time Armorica was separated from Laurussia by the Rheic Ocean.
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Various theories describe the past history of Tasmania in relation to other continental masses. Most models have the south west Tasmania abutting East Antarctica. In the missing link model, Z. X. Li has south west China positioned off the east coast of Tasmania with rifting at , with the Kamding dykes in China matching some granites from Tasmania. Tasmania can be subdivided into two terranes, separated by the Tamar Fracture System, on a line from the Tamar River to Sorell in the south east.
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In the Mesozoic, Late Jurassic Africa started moving east, and the Alpine Tethys opened. Subsidence related to this caused deep deposits of sediments on the east and some sediment remnants in pop downs in central parts of Spain. Two stages of rifting occurred in the east, one from Later Permian to Triassic, and the second from Late Jurassic to early Cretaceous. On the south side deposits of carbonates and clastic sediments formed a shelf in shallow water during late Triassic and Liassic times.
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From 250 to 150 Ma, Pangaea covered the Earth's surface, forming one super continent and one gargantuan ocean. During the breakup of Pangaea from 150 to 130 Ma, the Atlantic Ocean began to form the "Atlantic Gateway". Geological records from both the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP) support the enhancement of the CTM by the rifting of the Atlantic Ocean. Rising atmospheric carbon dioxide is thought to have been enhanced by the changing geography of the oceans.
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Rifting continued in the eastern part of the country during the Early Jurassic as the eastern United States drifted apart from Greenland and Europe. The Pacific Plate forced its way under the North American plate, triggering geologic upheaval, including volcanism, on the west coast. Ichthyosaurs remained the dominant marine reptiles of the Early Jurassic, but as the Jurassic progressed that title was gradually transferred to the plesiosaurs. The stratigraphic unit known as the Morrison Formation was deposited during the Late Jurassic.
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The last period of heightened earthquake activity probably took place during the Triassic, 200 million years ago. During this time, the Ramapo fault, originally a thrust fault active during the creation of the Appalachian Mountains, was reactivated as the Atlantic Ocean was opening and the supercontinent of Pangaea was being torn apart. The fault became integrally involved in a period of intense rifting, slowly lowering the land to its east by more than nine kilometers to create the Newark Basin.Rance, Hugh.
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Cushetunk Mountain, a ring- shaped volcanic mountain between Sourland Mountain and the Watchungs, is of the same geologic lineage. The Metacomet Mountains in the Connecticut River Basin, another aborted rift valley, came into existence around the same time as the Watchungs, also through extrusive eruptions. While non-contiguous, the two ranges may be considered geologic cousins, having formed under similar circumstances during the rifting of Pangaea. The same erosive and tectonic forces which elevated the Watchungs also served to raise the Metacomets.
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Changjiang-Qionghai fault recorded the rifting of the oceanic basin in Late Paleozoic. Regarding the Gezhen shear fault, it transformed from ductile shearing in the beginning to brittle-ductile and finally to brittle shearing through several tectonic events. To be specific, it was ductile in nature during the South China Caledonian orogeny in which the large South China Block was formed. It then became brittle-ductile in nature in Late Paleozoic to Early Mesozoic when the Paleo-Tethyan oceanic basin was closed.
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Near Lake Superior these intrusive formations intermingle in a complex mosaic with the rocks of the associated North Shore Volcanics, which also are relics of the Midcontinent rifting event.Miller, Green, Severson, Chandler, & Peterson, Geologic Map of the Duluth Complex , (2001). The Duluth and Beaver Bay Complexes extend a short distance under Lake Superior south of the present lakeshore, but in most places along and near that shore their southern reaches are overlain by the North Shore Volcanic Group.Ojakangas & Matsch (1982), pp.
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These characteristics indicate that the Egret Member is dominated by marine-derived Type II organic matter deposited under reducing conditions. Hydrocarbons trapped throughout the Jeanne d'Arc Basin were mainly sourced from the prolific Egret Member. After accumulation and preservation of abundant organic matter in the Egret Member, three major sandstone units were deposited during two subsequent episodes of crustal rifting. The Jeanne d'Arc, Hibernia and Ben Nevis-Avalon sandstones provide numerous tilted and faulted hydrocarbon-bearing reservoirs throughout the Jeanne d'Arc Basin.
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The more active Eastern Volcanic Zone (EVZ) represents a rift jump, although it is unclear how the eastward propagation of the main rifting activity has occurred. The offset between the WVZ and the EVZ is accommodated by the South Iceland Seismic Zone, an area characterized by high earthquake activity. The EVZ transitions northward into the Northern Volcanic Zone (NVZ), which contains Krafla volcano. The NVZ is connected to the Kolbeinsey Ridge by the Tjörnes Fracture Zone, another major center of seismicity and deformation.
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The Upper Rhine Graben extends from the northern edge of the Jura mountains in the south up to the triple junction where the ECRIS branches. Rifting initiated here in the Oligocene but the northern and southern parts of the graben show distinct post-Oligocene histories. In the Miocene the southern part of the graben became uplifted, while the northern part continued to subside into the Pleistocene. Currently the Upper Rhine Graben is thought to be experiencing dextral strike-slip reactivation.
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Volcanism of the Chukotat Group might have originated from rifting of a microcontinent that now forms the southwestern portion of Baffin Island. Map showing the age of geologic features related to the Circum-Superior Belt. Geologic features include: 1 = Carbonatite feeder, 2 = Montagnais gabbro sills, 3 = rhyodacite, 4 = Chukotat volcanics, 5 = Belcher and Sleeper Island sills, 6 = Fox River sill, 7 = Molsen dikes, 8 = Thompson belt mafic-untramafic magmatism, 9 = Winnipegosis komatiite, 10 = Hemlock formation, 11 = Gunflint formation, 12 = Pickle Crow dike.
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1989; Cawood et al. 2001), and the southern portion (between Laurentia and now-South America) may not have finish until 550 Ma. # Metamorphic/Deformation Event of Unknown Cause: Upper-crustal folding, faulting, and mineral foliation during the Late Neoproterozoic / Early Cambrian (612–544 Ma); it is unclear whether this represents a regional or local event, or event what the event was. Proposed possible causes include back-arc rifting or closure, subduction of another block, or collision of the Charlotte and Carolina terranes.
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At that time, the craton was rotated approximately 90° clockwise from its present orientation, and was located south of the equator. The rifting process thinned the crust and led to volcanic activity, resulting in a layer of basalt, today known as the Catoctin formation, burying the existing ridges and valleys.Richard P. Tollo, James McLelland, Louise Corriveau, Mervin J. Bartholomew (ed.), "Proterozoic tectonic evolution of the Grenville orogen in North America," in The Geological Society of America Memoir No. 197, p. 454 (2004).
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Rifting started to create the Gulf of California far to the south 6 to 10 million years ago. Around the same time, the western edge of the Colorado Plateau may have sagged slightly. Both events changed the direction of many streams toward the sagging region and the increased gradient caused them to downcut much faster. From 5.5 million to 5 million years ago, headward erosion to the north and east consolidated these streams into one major river and associated tributary channels.
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Huge slopes made of fractured basalt scree are visible beneath many of the ledges of Sleeping Giant. The basalt cliffs are the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa. These basalt floods of lava happened over a period 20 million years. Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows, which eventually lithified into sedimentary rock.
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The final rifting of the Levant Basin happened in the Late Jurassic. The Arad Group of dolomite, limestone and marl in Lebanon is virtually identical to similar units of the same age in the Syrian Coast Ranges. A large erosional event in the Kimmeridgian led the ocean to retreat westward, resulting in erosion. Mantle plumes may have been present beneath the Levant in the Late Jurassic, which is posited as an explanation for the alkaline volcanic rocks found in Mount Lebanon.
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Inside the volcano resides a magma chamber from which molten magma periodically bursts into a swarm of fissures that cut through the volcano from north to south. The recent activity was characterized by periods of slow land rise, interspersed by shorter periods of rapid subsidence, underground magma bursts, rifting, earthquakes and eruptions (nine in all). This is an excellent example of the process of continental drift in Iceland. A central volcano and its associated fissure swarm is called a volcanic system.
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East Gondwana then began to break apart about 115–120 million years ago when India began to move northward.Plummer, P. S., and E. R. Belle (1995), Mesozoic tectono–stratigraphic evolution of the Seychelles microcontinent, Sedimentary Geology, 96, 73–91. Between 84–95 million years ago rifting separated Seychelles and India from Madagascar. Since its formation the Madagascar block has moved roughly in conjunction with Africa, and thus there are questions as to whether the Madagascar Plate should be still considered a separate plate.
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The source of the Fly Geyser field's heat is attributed to a very deep pool of hot rock where tectonic rifting and faulting are common. The first geyser at the site was formed in 1916 when a well was drilled seeking irrigation water. When geothermal water at close to boiling point was found, the well was abandoned, and a calcium carbonate cone formed.Fly Gerser In 1964 a geothermic energy company drilled a second well near the site of the first well.
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The location of the triangle (the shaded area in the center of the map) and the local fault lines. It is located at The Afar Triple Junction (also called the Afro-Arabian Rift System) is located along a divergent plate boundary dividing the Nubian, Somali, and Arabian plates. This area is considered a present-day example of continental rifting leading to seafloor spreading and producing an oceanic basin. Here, the Red Sea Rift meets the Aden Ridge and the East African Rift.
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Mongolia has complicated tectonic and structural geology, belonging to the Mongolian-Okhotsk Mobile Zone, between the Siberian Platform and Chinese Platform. The basement rocks formed during the Paleozoic in the Precambrian as Riphean age ophiolite formations experienced rifting from 1.7 to 1.6 billion years ago and again around 800 million years ago. The closing of a late Proterozoic ocean generated the ophiolites and the oldest basement rock. The Baikalides and Altaid mountain belts represent the accretion of island arcs into the Paleozoic.
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At the beginning of the Cenozoic, through the Paleocene and Eocene, similar deposition to the Cretaceous took place, including bituminous limestone and marl. Rifting began in the Oligocene, forming the Jordan Rift Valley. The resulting depression was probably occupied by a sequence of lakes or shallow marine environments. From the Miocene through the Pliocene, a marine environment that may have been a branch of the Mediterranean reached the Red Sea through the Rift Valley, reaching basalt flows in Djebel ed Drouz.
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During the Wopmay orogeny, subduction occurred as oceanic crust of the Slave Craton was subducted beneath an eastward moving continental plate. Likewise, during the Trans-Hudson orogeny, rifting at first separated the Superior craton from the rest of the continent. Then the Superior Craton reversed its direction and the ocean basin began to close. A subduction zone formed as the oceanic crust of the Superior Craton was subducted beneath the Hearne and Wyoming Craton with the Sask Craton in the middle.
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Topography of the Black Forest The Black Forest consists of a cover of sandstone on top of a core of gneiss and granites. Formerly it shared tectonic evolution with the nearby Vosges Mountains. Later during the Middle Eocene a rifting period affected the area and caused formation of the Upper Rhine Plain. During the last glacial period of the Würm glaciation, the Black Forest was covered by glaciers; several tarns (or lakes) such as the Mummelsee are remains of this period.
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Talus slope on Bare Mountain Bare Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The lava from which the mountain is formed was erupted in the early Jurassic Period when North America was rifting apart from Africa and Eurasia. The lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the dramatic cliffs and ridges of Bare Mountain.
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In some cases, the heated groundwater may rise along extensional faults related to rifting in the Northern Cordilleran Volcanic Province. The Lakelse Hot Springs near Lakelse Lake Provincial Park in northern British Columbia is interpreted to be one such example. With a temperature of , the springs are the hottest in Canada. It is also possible the magma associated with the Nass Valley eruption 250 years ago to the north rose along the same north trending fault lines fueling the Lakelse Hot Springs.
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This led to the formation of a back arc basin, the Black Sea. The start of this subduction is responsible for the unconformity between the Kilimi and Cemaller formations and marks the beginning of the Alpide orogeny in the region. The andesitic volcaniclastic sediments of the Yemislicay support the subduction of oceanic crust in the region during this time. The Zonguldak basin was able to sustain deposition after the start of the Alpide orogeny due to rifting in the Black Sea basin.
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Badb Linea is the third rift zone and consists of closely spaced, linear grabens trending in a north-south direction. However, unlike the other rifts, Badb Linea has structures which both truncate and cross-cut the Irnini flows, signifying that its rifting occurred before and after the Irnini flows. The abundance of tectonic structures (e.g. wrinkle ridges, graben, and tessera) in proximity to Irnini Mons provides indications for the regional stress orientation of the shallow crust, as well as local timelines.
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St. Mary's Islands, also known as Coconut Island and Thonsepar, are a set of four small islands in the Arabian Sea off the coast of Malpe in Udupi, Karnataka, India. They are known for their distinctive geological formation of columnar rhyolitic lava (pictured). Scientific studies indicate that the basalt of the St. Mary's Islands was formed by sub-aerial subvolcanic activity, because at that time Madagascar was attached to India. The rifting of Madagascar took place around 88 million years ago.
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During the Late Cretaceous, a sequence of flood basalts up to 200 m thick covered Permo-Triassic and Lower Cretaceous sedimentary sequences. These basalt flows cover a wide area of the basin and form the Antanimena and Bongolava-Manasamody plateaus. During the Early Cenozoic, Madagascar experienced regional uplift and intracontinental rifting. This can be evidenced by the development of several graben or half graben systems throughout the island as well as the uplift in the central backbone of the island.
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Mirovia or Mirovoi (from Russian мировой, mirovoy, meaning "global") was a hypothesized superocean which may have been a global ocean surrounding the supercontinent Rodinia in the Neoproterozoic Era, about 1 billion to 750 million years ago. Mirovia may be essentially identical to, or the precursor of, the hypothesized Pan-African Ocean, which followed the rifting of Rodinia. The Panthalassa (proto-Pacific) Ocean developed in the Neoproterozoic Era by subduction at the expense of the global Mirovia ocean. A reconfiguration of the supercontinent Rodinia.
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Development of the Bransfield Rift, depicting trench rollback and upwelling of displaced mantle material. The last and most recent stage in the evolution of the Antarctic Peninsula subduction zone is the opening of the Bransfield Rift, creating the Bransfield back-arc basin from the Oligocene to the present day. This basin separates the inner, older magmatic arc (mainland Antarctic Peninsula) from the outer, younger magmatic arc (South Shetland Islands). Alkaline and tholeiitic volcanic activity is associated with this rifting event.
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The Nosib Group is charactererized by interbedded marine and continental sediment capped by volcanics. In the USGS stratigraphic column this is associated with the uplift of the Katangan orogeny 880 Ma, created during the series of rifting and compression of the Congo and Kalahari Cratons during the formation of the Gondwana supercontinent. The Owambo Basin is thought to originate at this time as a pull-apart basin filled with sediment from the surrounding uplifted areas, and eventually as a shallow marine system.
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Map of Pangaea with modern continental outlines The supercontinent cycle is the quasi-periodic aggregation and dispersal of Earth's continental crust. There are varying opinions as to whether the amount of continental crust is increasing, decreasing, or staying about the same, but it is agreed that the Earth's crust is constantly being reconfigured. One complete supercontinent cycle is said to take 300 to 500 million years. Continental collision makes fewer and larger continents while rifting makes more and smaller continents.
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The hotspot drifted from the Pacific Plate to the Nazca Plate approximately 1.2 million years ago and a seamount chain began to develop on the Nazca Plate. As the hotspot continued to migrate, rifting of the Nazca Plate developed along its track. This boundary is now known as Dietz Deep Volcanic Ridge, which extends to the northeast and grows at a velocity of 39 mm/year. The Dietz Deep Ridge terminates at the Dietz Deep Basin, an extensional feature with high elevational relief.
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The Tethyan Himalayan sequence is composed of mainly siliciclastic and carbonate sedimentary rocks deposited from 1840 Ma to 40 Ma. These are inter-bedded with volcanic rocks of Paleozoic and Mesozoic age. This sequence is divided into several sub-units due to the different lithofacies present in the sequence. The lithofacies of the rocks are a result of the shift in the depositional environment. Specific to this sequence, the Carboniferous to Jurassic rifting event was the cause of the changing depositional environment.
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NFB is the product of the asymmetric back-arc opening about a hinge point at 11°S, 165°E around which the Vanuatu chain has rotated 28° clockwise during the last 6 Ma, or 6–7.5°/Ma. This rotation has also caused rifting in the northern part of the NFB. Vanuatu can be divided into a southern and a northern tectonic blocks separate from the western NFB block. These blocks are separated by an extensional zone east of the islands chain.
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The Little Salmon River formed as a result of a rift valley developing between the Rocky Mountains and the Columbia Plateau section of the Intermontane Plateaus. Columbia River basalts underlie much of the western and central parts of the watershed, while other types of volcanic rock of closer origin form the foundations of the eastern mountains. The entire watershed is dissected by fault-block rifting. The water table is high and soils are generally well drained and of volcanic origin.
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He was also involved in geothermal monitoring of Mount Ruapehu and the monitoring of rifting in the Taupo Volcanic Zone. Grindley was a member of geological survey teams in Antarctica in 1961–62, 1977–78, and 1981–82, involved in paleomagnetic surveys and geological mapping. He was the senior geologist of the northern party of the New Zealand Geological Survey Antarctic Expedition in 1961–62, which named the Grindley Plateau in the Queen Alexandra Range in his honour. Grindley retired in 1987.
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The Santa Fe Group is widely defined as basin-filling sedimentary and volcanic rocks of the Rio Grande rift. These range in age from late Oligocene to Pleistocene. The oldest formations in the group correspond to the earliest structural deformation associated with rifting. Geologic uplift of the region around the rift has ended deposition, and erosion in the Rio Grande river system has exposed many of the beds deposited earlier, often spectacularly, as in the badlands north of Santa Fe.Galusha and Blick 1971, p.
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Magnetic anomalies from the seamount indicate that it was the site of highly irregular activity, with differences in the rifting there being up to . A gap near the seamount, known as the Ballons gap, is interpreted as being due to excess volcanism from the seafloor spreading process. A ridge just south of the seamount, the Antipodes Fracture Zone, is interpreted as having been built by a combination of compression and volcanic activity associated with the triple- junction Bellingshausen-Marie Byrd Land plate boundary nearby.
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This shows a possible configuration for the attachment of the Wyoming and Superior provinces at 2,100 million years ago. Note the Blue Draw Metagabbro (BDM), marked by the red dot, on the Wyoming province. The 2,170-million-year-old intrusive events that affected the Superior and the Wyoming cratons indicate that the plume had moved west, centered in the opening between the Superior province and the rifting Wyoming province. The Wyoming province was rotating away, with the Blue Draw Metagabbro being the pivot point.
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The Jemez Mountains lie on the intersection of the western margin of the Rio Grande Rift and the Jemez Lineament.Aldrich 1986Whitmeyer and Karlstrom 2007 Here magma produced from the fertile rock of an ancient subduction zoneWolff et al. 2004 has repeatedly found its way to the surface along faults produced by rifting. This has produced a long-lived volcanic field, with the earliest eruptions beginning at least 13 million years ago in both the northern (Polvadera Group) and southern (Keres Group) portions of the volcanic field.
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American Association of Petroleum Geologists, Tulsa, Oklahoma. More recently, the Zenith Plateau is inferred to be a volcanic plateau that consists of a thick sequence of highly attenuated, stretched, and faulted volcanic margin crust formed during the time of the continental break-up of Gondwana. This crust is inferred to be buried by voluminous volcanic deposits that immediately followed its formation. Later on, complicated tectonic activity that was associated with local rifting and sea floor spreading separated the Wallaby and Zenith plateaus from Australia and each other.
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Where the thickness of the crust and lithosphere varies, equilibrium must be reached. Isostatic compensation and gravity anomalies result from balance between mass excess of the extra mantle beneath the thinned lithosphere and the overlying low-density crust. Positive gravity anomalies result from the relatively low flexural strength of the lithosphere during the beginning of rifting. As the passive margin matures, the crust and uppermost mantle become colder and stronger, so that the compensating deflection in the base of the lithosphere is broader than the actual rift.
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In the late Cretaceous rifting transitioned to seafloor spreading marking the onset of post-rift passive margin conditions within the Otway Basin. As Australian-Antarctic plate clearance continued and the passive margin developed further the basin experienced widespread thermal subsidence leading to an increase in accommodation space. Deposition from the late Maastrichtian to present day is marked by a succession of marine and carbonate accumulations of the Wangerrip, Nirranda, Heytesbury, and Whalers Bluff Groups, separated by distinct unconformities associated with basin-wide compression events.
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The supercontinent Pangaea was rifting during the Triassic—especially late in the period—but had not yet separated. The climate of the Triassic was generally hot and dry, forming typical red bed sandstones and evaporites. There is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate, a climate suitable for reptile-like creatures. Pangaea's large size limited the moderating effect of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters.
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Suggestions include back-arc rifting, foredeep flexure, mantle plumes and the breakup of a microcontinent. The geochemical indication of the Circum-Superior Belt is also poorly known; either it contains major regional differences or it is the same throughout the magmatic zone. With the discovery of the Pickle Crow dike swarm throughout the western Superior craton, the likelihood of other 1,880 million year old dike groups throughout the Superior craton remains. This is partly because several dike zones in the Superior craton remain undated.
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Trending along the north side of Lancaster Sound is a major steeply dipping normal fault called the Parry Channel Fault. As much as of vertical displacement took place along this fault during the Eurekan Rifting Episode. The Northern Baffin and Admiralty faults trend along the south side of Lancaster Sound, the former of which is dominant. It extends from Admiralty Inlet in the west then trends eastward along the north coasts of Baffin and Bylot islands to Baffin Bay where it possibly connects with other rift structures.
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Like many rifts worldwide, the Canadian Arctic Rift System was a site of magmatic activity during active tectonism. This activity was associated with seafloor spreading in the Baffin and Labrador basins as well as continental rifting within the Arctic Archipelago. Several episodes of intrusive and extrusive activity took place from the Paleozoic to Cenozoic with the emplacement of dikes, sills, lava flows and pyroclastic rocks. The Sverdrup Basin Magmatic Province in the east- central Sverdrup Basin is an Early Cretaceous to Paleogene large igneous province.
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Nickel, copper and platinum group elements formed in ultramafic intrusions within the Nikolai Formation, deposited as gabbro, pyroxenite and dunite as the Kluane mafic-ultramafic complex. During the Triassic, rifting may have briefly separated the two terrains before they rejoined, a possibility inferred from the Duke River Fault "suture" between the two terranes. The two terranes have overlap assemblages with rocks formed across the two landmasses. The thick Dezadesh Formation turbidite and tuff deposited in a basin from the late Jurassic into the early Cretaceous.
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These plutons slowly cooled to form the Zoroaster Granite; part of which would later be metamorphosed into gneiss. This rock unit can be seen as light-colored bands in the darker garnet-studded Vishnu Schist (see 1b in figure 1). The intrusion of the granite occurred in three phases: two during the initial Vishnu metamorphism period, and a third around 1.4 billion years ago. The third phase was accompanied by large-scale faulting, particularly along north–south faults, leading to a partial rifting of the continent.
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The former Black Angel zinc and lead mine is located within the Karrat Group carbonates on the coast of West Greenland. Ultramafic sills are found in the southern Baffin Island Lake Harbour Group. On the Belcher Islands in Hudson Bay are clastic rocks overlain by volcanic and carbonate rocks, which record subsidence and rifting at the western edge of the Superior Craton. Thermal overprinting and deformation from the Paleoproterozoic have been found in these rocks, dating to the Trans-Hudson Orogeny 1.8 billion years ago.
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The oldest rocks in North Carolina are part of the Grenville Province, which stretches from Texas to Labrador and which was impacted by the Grenville orogeny in the Mesoproterozoic to form the Appalachian Mountains. Grenville age rocks are exposed in the Blue Ridge province and the Sauratown Mountains. The Bakersville mafic dike swarm from 734 million years ago along with the peralkaline granites of the Crossnore Complex and bimodal volcanic rocks atop the crystalline basement point to the rifting of the proto-North American continent Laurentia.
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In 1965, Canadian geologist John Oliver Wheeler foresaw the need for a volcanological program in Canada's western Cordillera. Souther was given the job of working on the Mount Edziza complex with the able assistance of Maurice Lambert. By 1970, the two geologists had established that eruptions of alkali basalt, followed by extrusion of silicic peralkaline lavas, had occurred episodically at Edziza for the past 10 million years and that volcanism was accompanied by east-west extension and incipient rifting. However, the regional tectonic context was still unresolved.
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The rift system may have been the result of extensional forces behind the continental collision of the Grenville Orogeny to the east which in part overlaps the timing of the rift development. Later compressive forces from the Grenville Orogeny likely played a major role in the rift's failure and closure. Had the rifting process continued, the eventual result would have been sundering of the North American craton and creation of a sea. The Midcontinent Rift appears to have progressed almost to the point where the ocean intruded.
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Like the Udokan plateau, Jom-Bolok is a volcanic field part of the Baikal rift which has been volcanically active during the Holocene. Volcanism there may be the consequence either of passive rifting or mantle plume activity and has been ongoing since the Mesozoic. The basement of this area was heavily folded and altered during the Tertiary, which was also affected by river incision and earlier eruptive activity. During the late Pleistocene, thick glaciers formed in the Jom-Bolok valley and other adjacent valleys.
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Oscillating marine transgressions in the Rhaetian to Middle Jurassic shifted deposition from delta sands to offshore mudstones and regional updoming took place at the junction of the Central Graben, Moray Firth and Viking Graben. Deltas were drowned and replaced with deepwater basins and major rifting in the Late Jurassic produced block tilting. Sedimentation shifted in Albian through Danian times from siliclastic to carbonaceous, marked by marl and glauconite sandstones. Sea level fell in the Maastrichtian, restricting the sea to deeper areas of the Central Graben.
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Rifting is said to have begun in the Late Cretaceous epoch to Paleogene period. At that time the African plate was experiencing far-field stresses caused by portions of the northern boundary of the African plate subducting under the Eurasian plate. Today, the Arabian plate is experiencing a crustal down pull, or slab pull, that has separated from the African plate. At the same time of the subduction in the north there was mantle upwelling causing the crust to down warp and swell into domes.
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Another hypothesis involves extensive sea floor rifting and metamorphic decarbonation reactions releasing considerable amounts of carbon dioxide to the atmosphere. At the end of the Middle Eocene Climatic Optimum, cooling and the carbon dioxide drawdown continued through the late Eocene and into the Eocene–Oligocene transition around 34 million years ago. Multiple proxies, such as oxygen isotopes and alkenones, indicate that at the Eocene–Oligocene transition, the atmospheric carbon dioxide concentration had decreased to around 750–800 ppm, approximately twice that of present levels.
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The Jemez Mountains lie on the intersection of the western margin of the Rio Grande Rift and the Jemez Lineament.Aldrich 1986Whitmeyer and Karlstrom 2007 Here magma produced from the fertile rock of an ancient subduction zoneWolff et al. 2004 has repeatedly found its way to the surface along faults produced by rifting. This has produced a long-lived volcanic field, with the earliest eruptions beginning at least 13 million years ago in both the northern (Polvadera Group) and southern (Keres Group) portions of the volcanic field.
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The Jemez Mountains lie on the intersection of the western margin of the Rio Grande Rift and the Jemez Lineament.Aldrich 1986Whitmeyer and Karlstrom 2007 Here magma produced from the fertile rock of an ancient subduction zoneWolff et al. 2004 has repeatedly found its way to the surface along faults produced by rifting. This has produced a long-lived volcanic field, with the earliest eruptions beginning at least 13 million years ago in both the northern (Polvadera Group) and southern (Keres Group) portions of the volcanic field.
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The ASP hotspot was originally located beneath Australia and a chain of seamounts connecting it to the southern end of the Ninety East Ridge, i.e. the ASP hotspot track, indicate it probably contributed to the formation of the Ninety East Ridge before the SEIR opened. The opening of the Southern Ocean began west of Australia around 100 Ma from where it propagated eastward at about 2 cm/yr. This rifting was not the direct product of hotspot interaction as it occurred over a cooler than normal mantle.
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During the Taconic orogeny, more igneous intrusions and metamorphism occurred as the ancestral Taconic Mountains were pushed up. The sediments that were deposited in a sea between an island-arc and the Iapetus eventually were squeezed and deformed along a subduction zone. The sediments deposited in that sea are now located in the Great Valley section. (See below) The sediments placed from the rifting of Rodinia became the roots of the ancestral Taconics and went through their first wave of metamorphism during the Taconic orogeny.
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Both the lower contact of the formation with the Ritito Conglomerate and the upper contact with the Chama-El Rito Member of the Tesuque Formation are gradational. The transition to the Ritito Conglomerate is characterized by thick chert beds, informally designated the Pedernal chert for outcrops around Cerro Pedernal (). Individual beds in the formation thicken across the Canones fault zone, which separates the Colorado Plateau from the Rio Grande rift. This indicates that the formation was deposited after rifting began within the Rio Grande rift.
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Initial rifting between the two continents is marked by the c. 650 Ma Egersund dike swarm in southern Norway and from 600 Ma they began to rotate up to 180° relative to each other, thus opening the Iapetus Ocean between them. Laurentia quickly moved northward but Baltica remained an isolated continent in the Southern Hemisphere closer to Gondwana on which endemic trilobites evolved in the Early Ordovician. During the Ordovician, Baltica moved northward approaching Laurentia again allowing trilobites and brachiopods to cross the Iapetus Ocean.
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In western Laurentia (North America), a tectonic episode that preceded this rifting produced failed rifts that harboured large depositional basins in Western Laurentia. The global ocean of Mirovia, an ocean that surrounded Rodinia, started to shrink as the Pan-African ocean and Panthalassa expanded. Between 650 million and 550 million years ago, another supercontinent started to form: Pannotia, which was shaped like a "V". Inside the "V" was Panthalassa, outside of the "V" were the Pan-African Ocean and remnants of the Mirovia Ocean.
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Rifting began in the Late Cretaceous as a result of tectonic extension (stretching and thinning of the crust and mantle) in approximately an east–west orientation, by plate tectonics processes. The extension within the Ross Embayment occurred over four time periods and totals 500 kilometers or more, mostly before the late Miocene. The first phase happened in the east near Marie Byrd Land before the Campbell Plateau of Zealandia broke away from Antarctica in the Late Cretaceous.Lawver, L. A., and L. M. Gahagan. 1994.
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Sites such as the Wopmay Orogen provide evidence for early and ongoing plate tectonics. Traces of old oceanic crust, island arcs, and colliding continents indicate that the same forces at work today have been at work in the early Proterozoic and probably earlier. Alignments of magnetic particles in rocks demonstrate that continents were drifting across the surface of the Earth relative to the magnetic poles then as now, and that the ocean floor was rifting and subducting, all at least 1.5 billion years ago. Retrieved May 2016.
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Geological Survey India News. 1978. Soon after the rifting phase ended, the compressional phase took place where the eastern Bundelkhand craton subducted under the western Marwar craton. As collision continued, the subduction zone steepened, leading to the development of an island arc between the two cratons. After collision had proceeded for a certain period of time, the uplift of the Aravalli Supergroup was induced at around 1800 Ma. In the last stage of convergence, the thrust fault further steepened and the colliding blocks eventually become sutured.
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The Widmerpool Gulf is a name given to a sedimentary basin that existed as an area of open water during the Early Carboniferous (Tournaisian Age). It is named after Widmerpool, near Nottingham and was an extension eastwards as far as Lincolnshire, of the North Staffordshire Gulf. It was formed during a rifting event, which began in the Late Devonian, that affected the area between the London-Brabant Massif to the south and the Highland Boundary Fault to the north.Waters, C.N., Browne, M.A.E., Dean, M.T., and Powell, J.H., 2007.
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Volcanic activity has occurred in parts of Iran since the Cretaceous period. During the Eocene and Oligocene epochs, volcanic activity reached its maximum, with thick pyroclastic layers being deposited in central Iran and the Alborz mountains. The area around Taftan volcano belongs to a tectonic zone which is variously referred to as the Sistan suture or the Zabul-Baloch zone. There, after a previous episode of rifting and subsequent formation of an ocean, the Neh and Lut tectonic blocks collided during the Eocene epoch after a subduction episode that commenced in the Maastrichtian age.
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The Upper Sardinia Margin is a fault-bounded passive margin located northwest of the Vavilov Basin. Seismic reflection surveys across the Upper Sardinia Margin exhibit a stratigraphic geometry suggestive of pre-rift, syn-rift, and post-rift sequences. Drill cores penetrating to the base of the syn-rift sediments identified a transgressive sequence related to subsidence of the continental crust during the rifting stage of the Tyrrhenian Basin opening. At the base of the syn-rift sequence are 60 meters of Tortonian conglomerate with subrounded clasts derived from metamorphosed carbonate and quartzitic basement.
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The basement rock of the Marsili Basin is vesicular basalt. Due to the abundance (10–30% of rock volume) and size (up to 3 or 4 mm) of the vesicles, it is likely that the basalt was emplaced as a flow rather than a sill. Overlaying the basement is 250 meters of calcareous mud and ooze with interbedded volcanoclastic layers. Benthic foraminifera and magnetic anomaly data from the base of this section constrain the terminus of rifting between 1.67 and 1.87 Ma. At the top of the stratigraphic section are 350 meters of volcanoclastic turbidites.
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The geology of Morocco formed beginning up to two billion years ago, in the Paleoproterozoic and potentially even earlier. It was affected by the Pan- African orogeny, although the later Hercynian orogeny produced fewer changes and left the Maseta Domain, a large area of remnant Paleozoic massifs. During the Paleozoic, extensive sedimentary deposits preserved marine fossils. Throughout the Mesozoic, the rifting apart of Pangaea to form the Atlantic Ocean created basins and fault blocks, which were blanketed in terrestrial and marine sediments—particularly as a major marine transgression flooded much of the region.
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The Senegal sedimentary basin, also known as the Senegal- Mauritania Basin, formed as the largest marginal basin in Africa during the rifting apart of the center of the supercontinent Pangaea to form the Atlantic Ocean in the Mesozoic. The basin is 1400 kilometers from north to south and 500 kilometers at its maximum width at Dakar. This Atlantic-type half-basin has gently dipping sedimentary units that get thicker closer to the coast. Due to overlying sediments from the Oligocene to modern times, its exact structure and origins are unclear.
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A view of Crow's Nest from across the Potomac River The mid-Atlantic Ridge started to form in the early Jurassic period (175 million years ago), breaking apart the super continent Pangaea and beginning the expansion of the modern Atlantic Ocean. It has widened steadily to its present size. This rifting event separated North America from Africa, and the area known today as Virginia became the trailing edge of the newly formed North American continent. The Jurassic Period is found in the Mesozoic Era, or the Age of the Dinosaurs.
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New England is a region in the North Eastern United States consisting of the states Rhode Island, Connecticut, Massachusetts, New Hampshire, Vermont, and Maine. Most of New England consists geologically of volcanic island arcs that accreted onto the eastern edge of the Laurentian Craton in prehistoric times. Much of the bedrock found in New England is heavily metamorphosed due to the numerous mountain building events that occurred in the region. These events culminated in the formation of Pangaea; the coastline as it exists today was created by rifting during the Jurassic and Cretaceous periods.
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The North Rupununi is situated on the Guiana Shield, precambrian rock with a complex geology that includes plutonic, volcanic, metamorphic and sedimentary rocks and various rifting, uplifting, sedimentation and erosion events. The geology of the North Rupununi is critical because it fundamentally defines the topography, soils, hydrology and ultimately the economy of the area. The North Rupununi is part of a Mesozoic graben, the Takutu Basin. The basin is 280 kilometers long and 40 kilometers wide, is over 7 kilometers deep, and covers more than 11,200 square kilometers in Guyana and Brazil.
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Sedimentation took place after the ophiolite emplacement and magmatism of the South China Sea related to the Mesozoic western Pacific subduction. The sedimentation shows transition from deep marine mudstones and turbidites in the Paleogene to shallow marine sandstones, deltaic fluvial and carbonates during the Miocene and into the Pliocene. This gives evidence supporting changes to the environmental setting that occurred due to rifting, uplift and sedimentation events. The Rajang Group and Kinabatangan Group are characterised by the deep marine sediments while the Serudong Group is made up of sediments deposited in a shallower marine environment.
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The Chocolay Group - up to thick - is a shallow-marine layer which was deposited on the Archean basement; deposition in the Chocolay Group began 2,207 ± 5 million years ago and ended 2,115 ± 5 million years ago. The Menominee Group is a foredeep deposit whose layers were deposited in second-order basins created by oblique subduction of the continental margin, rather than in basins formed on a rifting margin. The upper Baraga Group represents deeper marine basins resulting from increased subsidence and continued collision. Deposition continued until when the Penokean orogeny began.
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This mountain is located in the Sanandaj-Sirjan geological and structural zone. Sanadaj-Sirjan was subjected to magmatism and metamorphism in the Paleozoic and Mesozoic. This section along with other Iranian microplates were separated from Gondwana in the Carboniferous (when magmatism was caused by rifting and the process of detachment) and moved northwards. From the Early Jurassic to the Middle Miocene Sandaj-Sirjan was adjacent to a subduction zone and there was magmatism because of the subduction zone which was situated in the south and south-west of this structural zone.
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The era began in the wake of the Permian–Triassic extinction event, the largest well-documented mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event, another mass extinction whose victims included the non-avian dinosaurs. The Mesozoic was a time of significant tectonic, climate, and evolutionary activity. The era witnessed the gradual rifting of the supercontinent Pangaea into separate landmasses that would move into their current positions during the next era. The climate of the Mesozoic was varied, alternating between warming and cooling periods.
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Lawrence A. Frakes and John C. Crowell. 1969. Late Paleozoic Glaciation: I, South America, GSA Bulletin During the early rifting stages of the South Atlantic the area of southern Paraná Basin suffered a gentle uplifting that deviated sediments into the Tacuarembó region of Uruguay. These changes led to the formation of the Itacuanbú and Tacuarembó formations during the Mid Jurassic to Early Cretaceous. Parts of the Tacuarembó formation came to be preserved thanks to a unit of the Paraná traps, the Arapey basalts, that erupted 132 mya and covered the sediments.
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A correlation was proposed between the episodic formation of UHT metamorphic rocks and the episodic assembly of supercontinents in the Precambrian.note-Brown2007-2 note- Santosh%26Omori2008a-4 (malformed ref) However, inspection of extreme metamorphism at convergent plate margins indicates that supercontinental assembly is associated with regional HP to UHP eclogite-facies metamorphism at low thermal gradients of less than 10 °C/km, whereas continental rifting plays a crucial role in causing regional HT to UHT granulite-facies metamorphism at high thermal gradients of greater than 30 °C/km.Zheng, Y.-F., Chen, R.-X.
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The African Plate is a major tectonic plate straddling the equator as well as the prime meridian. It includes much of the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges. Between and , the Somali Plate began rifting from the African Plate along the East African Rift. Since the continent of Africa consists of crust from both the African and the Somali plates, some literature refers to the African Plate as the Nubian Plate to distinguish it from the continent as a whole.
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The Northern Cordilleran Volcanic Province (sometimes called the Stikine Volcanic Belt) is the most active volcanic region in Canada, containing more than 100 volcanoes. Several eruptions are known to have occurred within this region in the past 400 years and contains Canada's largest volcanoes. It formed as a result of faulting, cracking, rifting and the interaction between the Pacific and the North American plates. The Chilcotin Group in southern British Columbia is thought to have formed as a result of back-arc extension behind the Cascadia subduction zone.
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Queen Charlotte Sound as delineated by BC Geographical Names, along with Hecate Strait and Dixon Entrance. Rifting and crustal extension in Queen Charlotte Sound up to about 17 million years ago has been linked to the Early Miocene passage of the Anahim hotspot. Yorath and Chase (1981) proposed that subcrustal melting above the Anahim plume resulted in weakening of the regional crust, setting the stage for rift development. Later, widespread volcanism produced subearial basalt and rhyolite flows in the region of the rift and along transcurrent faults that extend towards the northwest.
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The Arabian Plate was part of the African Plate during much of the Phanerozoic Eon (Paleozoic–Cenozoic), until the Oligocene Epoch of the Cenozoic Era. Red Sea rifting began in the Eocene, but the separation of Africa and Arabia occurred approximately in the Oligocene, and since then the Arabian Plate has been slowly moving toward the Eurasian Plate. The opening of the Red Sea rift led to extensive volcanic activity. There are large volcanic fields called the Older Harrats, such as Harrat Khaybar and Harrat Rahat, cover large parts of the western Arabian Plate.
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The Landers earthquake and the other large quakes associated with it in the Mojave region have been attributed to two possible long-term trends. One of these is that the San Andreas Fault may be in the process of being replaced as the plate boundary (between the North American Plate and the Pacific Plate) by a new trend across the Mojave and east of the Sierra Nevada Mountains. The other is that these quakes were a manifestation of the propagation of rifting coming up from the Gulf of California. Research is ongoing.
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During the Mesozoic Era, the supercontinent Pangaea began to rift apart, forming the Gulf of Mexico basin within the late Triassic and early Jurassic periods. The rifting was accompanied by volcanic and nonmarine deposition. Later, because the newly formed basin was shallow and restricted from the Atlantic Ocean, the expansive salt evaporite deposits that the Gulf of Mexico is known for were created whenever saltwater periodically inundated the basin and then evaporated during the middle Jurassic. Not until the late Jurassic was the Gulf of Mexico connected to the Atlantic Ocean.
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The Indian Craton was once part of the supercontinent of Pangaea. At that time, what is now India's southwest coast was attached to Madagascar and southern Africa, and what is now its east coast was attached to Australia. During the Jurassic Period about 160 Ma (ICS 2004), rifting caused Pangaea to break apart into two supercontinents, namely Gondwana (to the south) and Laurasia (to the north). The Indian Craton remained attached to Gondwana, until the supercontinent began to rift apart about in the early Cretaceous, about 125 million years ago (ICS 2004).
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Being part of the Transdanubian Range, the Úrkút Manganese Ore was linked to the environmental evolution of the southern passive margin of the rifting Tethys Ocean.Galácz, A., Horváth, F., & Voros, A. (1985). Sedimentary and structural evolution of the Bakony Mountains (Transdanubian Central Range, Hungary): palaeogeographic implications. Acta Geologica Hungarica, 28(1-2), 85-100. After Hettangian drowning and Sinemurian-Pliensbachian extensional tectonics and subsidence, along with pelagic sedimentation and submarine topography, a pronounced horst developed over the local sea, with a depth on the Pliensbachian-Toarcian Basin of 600 m.Galácz, A. (1988).
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The Chalk Group either directly overlies the impermeable uppermost Lower Cretaceous Gault Clay or permeable Upper Greensand Formation above the Gault Clay. Since its deposition, the chalk in southern England has been uplifted, faulted, fractured and folded by the distant effects of the Alpine Orogeny. The fracturing has greatly increased the chalk's permeability, such that it is a major aquifer. Sedimentary basins formed by rifting during the Triassic to Early Cretaceous were inverted during the Late Paleogene to Miocene leading to the formation of structures such as the Wealden Anticline and the Portland-Wight Monocline.
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The Otway Basin developed along the Australian Southern Rift System during late Jurassic to Cenozoic breakup of eastern Gondwana as Antarctica began rifting away from Australia. The basin lies at the transition from a normal-obliquely rifted continental margin to the west to a transform continental margin to the southeast. This transition zone is dominated by transtensional faulting that contributes to the basin's complex structural and depositional history. The margin developed through repeated episodes of extension and thermal subsidence leading up to, and following, the commencement of seafloor spreading between Australian and Antarctica.
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This suggests two possible mechanisms by which climate could influence tabular iceberg calving. First, non-uniform distributions in oceanic and atmospheric temperature may determine where the mélange melts and, thus, the location of the iceberg-calving margin. Second, melting or weakening of ice mélange as a consequence of climate change could trigger a sudden or widespread release of tabular icebergs and lead to rapid ice-shelf disintegration. Ice-shelf rifting, a long-term process that culminates in tabular iceberg release, is strongly influenced by sea ice and other types of ice, which fill the rift.
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Heating of the lithosphere, and the associated increase in buoyancy, is one possible mechanism proposed for the large degrees of uplift of the African superswell. Evidence of extensive volcanism and rifting in eastern Africa during the Cenozoic supports the idea that lithospheric heating was occurring during the time of uplift. Heat flow anomalies must be considered in order to justify lithospheric heating as a possible elevation mechanism in southern Africa. When comparing heat flow measurements in southern Africa mobile belts to average global heat flow values, a positive anomaly is observed.
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Paleogeography of the late Turonian (90 Ma) Burmese amber is retrieved from the Hukawng Valley, the geographical representation of the Hukawng Basin, a large Mesozoic-Cenozoic sedimentary basin in Kachin State of northern Myanmar. The strata have undergone folding and faulting. The basin is considered to be a part of the West Burma Block or Burma Terrane, which has a debated tectonic history. The block was part of Gondwana during at least the Early Paleozoic, but the timing of rifting is very uncertain, with estimates ranging from the Devonian to Early Cretaceous.
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The Franklin Mountains of Texas (previously known as Las Sierras de los Mansos) are a small range (23 miles long, wide) that extend from El Paso, Texas north into New Mexico. The Franklins were formed due to crustal extension related to the Cenozoic Rio Grande rift. Although the present topography of the range and adjoining basins is controlled by extension during rifting in the last 10 million years, faults within the range also record deformation during the Laramide orogeny, between 85 and 45 million years ago. The highest peak is North Franklin Peak at .
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During the Mesozoic, basins formed in what would become the Andean foothills, due to strike-slip movement and continental extension. The Choiyoi Group is a remnant of bimodal magmatism along a Paleozoic terrane suture. As the breakup of Gondwana began, narrow half-grabens filled with volcaniclastic rocks and the Pampa de Agnia Basin formed along the Gastre fault system. The Magallenes Basin experienced rifting and the Chon Aike province witnessed intraplate volcanism during the acceleration of the breakup around 180 to 165 million years ago, as the Weddell Sea opened.
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Gujarat lies 300–400 km from the plate boundary between the Indian Plate and the Eurasian Plate, but the current tectonics are still governed by the effects of the continuing continental collision along this boundary. During the break-up of Gondwana in the Jurassic, this area was affected by rifting with a roughly west–east trend. During the collision with Eurasia the area has undergone shortening, involving both reactivation of the original rift faults and development of new low-angle thrust faults. The related folding has formed a series of ranges, particularly in central Kutch.
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Bathymetric data suggest it is a possible graben structure with steep, linear, north-south margins that formed during the Eurekan Rifting Episode. The faults forming the supposed graben appear to have been guided in part by the structure of the Cornwallis Fold Belt, but probably were controlled ultimately by trends in the Precambrian crystalline basement. The Kaltag Fault is a northeast trending structure that extends along the continental margin northwest of the Queen Elizabeth Islands. It forms a boundary between the Canadian Arctic Rift System and other rifted structures to the northwest.
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The geology of Turks and Caicos includes the Turks and Caicos Bank, which together with the Florida-Bahamas Platform is a section of continental crust rifted away from North America during the rifting open of the Atlantic Ocean. Triassic sedimentary and volcanic rocks are inferred based on similar rocks in the Bahamas, overlain by Jurassic, Cretaceous and Paleogene limestone. During a drop in sea level during the Pleistocene glaciations, limestone was exposed as plateaus as sand dunes accumulated atop them and a karst landscape developed with caves and blue holes.
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These rocks were deposited during the rifting of Pangea during the Triassic and Jurassic Periods. Much of the northern segment of this region was glaciated and the resultant shaping help to form New York and Newark harbors. A small portion of the Pennsylvania Piedmont Highlands called the Trenton Prong extends into New Jersey through Trenton and are mostly Ediacaran and Cambrian aged rocks, that includes the Wissahickon Formation. The Manhattan schist exists in New Jersey, largely below New York harbor and in the vicinity of Bayonne and Jersey City.
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In many spots in Scandinavia basaltic dikes are found with ages between 670 and 650 million years. These are interpreted as evidence that by that time, rifting had started that would form the Iapetus Ocean. In Newfoundland and Labrador, the Long Range dikes are also thought to have formed during the formation of the Iapetus Ocean. It has been proposed that both the Fen Complex in Norway and the Alnö Complex in Sweden formed as consequence to mild extensional tectonics in the ancient continent of Baltica that followed the opening of the Iapetus Ocean.
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A rift valley lake deposited the mudstone and black shale of the middle unit—the Lockatong Formation—which holds extremely well preserved fossilized freshwater fish. This is, in turn, is overlain by the red-brown shale mudstone and sandstone of the Brunswick Formation which merges with the Hammer Creek Conglomerate. Because rifting thinned the crust, magma upwelled and intruded the basin, producing the feldspar and pyroxene dominant diabase of the Palisades Sill and an almost pure layer olivine up to six meters thick. The sill intruded 195 million years ago in the Early Jurassic.
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Hornsby is situated on the plateau, hence the namesake. Rock deposits in the Sydney area were tertiary freshwater sediments, which were a rough gravelly layer up to 8 metres thick located beneath silt and sand at a mean depth of 6 metres. As time went by, weathering transformed much of the sandy silt into siliceous clay. At the end of the Tertiary period, or about 80 million years ago, earth movements created an upheaval of 600 metres in most of coastal eastern Australia, due to the rifting and opening of the Tasman Sea.
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The Laramide orogeny was a major tectonic event that caused the most recent and significant deformation in the United States. The Subduction of the Farallon Plate beneath the North American Plate produced compression all across the western portion of the US. Crustal deformation occurred inland from the plate margin and it is mostly related to the deformation of northwestern United States. However this, in combination with Cenozoic rifting produced from the San Andreas fault, crustal folding, faulting and overall deformation have affected the southern regions of the continental US.
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Photograph of the first oil well in Comodoro Rivadavia The Golfo San Jorge Basin () is a hydrocarbon-rich sedimentary basin located in eastern Patagonia, Argentina. The basin covers the entire San Jorge Gulf and an inland area west of it, having one half located in Santa Cruz Province and the other in Chubut Province. The northern boundary of the basin is the North Patagonian Massif while the Deseado Massif forms the southern boundary of the basin. The basin has largely developed under condition of extensional tectonics, including rifting.
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Neoproterozoic rifting formed the Iapetus Ocean and the Cambrian Unicoi Formation and Chillhowee Group, from the early Paleozoic show a transition from terrestrial sandstone to marine sedimentary rocks. Small volcanic island arcs and pieces of oceanic crust, collectively known as terranes, accreted onto the edge of Laurentia with the shifting of the Iapetus, Rheic and Theic ocean basins. Folding, thrusting and compression resulted in a series of different mountain building events. The Taconic orogeny deformed and metamorphosed terranes in northwest North Carolina between 470 and 440 million years ago.
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The Austral (or Magallanes) Basin, is located on the southwestern end of the South American Plate and it is bordered to the south by the Scotia Plate covering an area of approximately . In the studied area, the Austral Basin underwent three main tectonic stages: (i) a rift stage; (ii) a thermal subsidence stage; and (iii) a foreland stage. The rifting stage is related to the break-up of Gondwana, grabens and half- grabens were formed and filled with volcaniclastic and volcanic rocks intercalated with epiclastic sediments of the El Quemado and Tobífera Formations.Santamarina et al.
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Examples of this type of architecture are illustrated in the main rift units of Statfjord North and Gyda Fields. The Visund fault block and the Oseberg-Brage infill are examples from marine half-grabens which are near the central or axial zones of the northern North Sea rift complex, far from the main hinterland areas and show deepening upward trends into basinal shales. The syn-rift unconformity describes the erosion surface that bevels fault blocks during continental rifting. It develops locally over individual fault blocks because of footwall uplift and lithospheric unloading by extension.
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In addition, the Viking Graben master faults bounding the East Shetland Platform to the west and the Horda Platform to the east acted as frontal shoulder faults during late Jurassic-early Cretaceous rifting. The early Cretaceous post-rift phase in the northern North Sea was characterized by slow subsidence, with much of the sedimentation accommodated by the infilling of previous rift bathymetry. At this time the shoulders of the rift were supported. During latest Cretaceous and Tertiary the shoulders lost their support, producing elongated, saucer-shaped basin and a 'steer's head' cross-sectional basin shape.
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The PRMB formed along the continental margin of South China as a result of continental rifting and sea floor spreading in the South China Sea area. The PRMB consists of two areas of depression between three areas of uplift, all running mostly parallel to the spreading axis. Major structures within the PRMB are classified as half- graben, narrow grabens, or wide grabens. Basement rock in the central and northern portions of the PRMB are Cretaceous and Jurassic granites, Mesozoic sedimentary rocks in the east, and Paleozoic quartzite in the west.
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The western end of the shear zone is obscured by the volcanoes of the Cameroon line, but based on reconstruction of the configuration of South America before it separated from Africa, the Foumban Shear Zone can be identified with the Pernambuco fault in Brazil. A major earthquake in 1986 could indicate that the shear zone is reactivating. The Benue Trough lies to the west of the Cameroon line. The Benue Trough was formed by rifting of the central West African basement, beginning at the start of the Cretaceous era.
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20 million years post-rifting, the North German Basin experienced a rapid accumulation of sediments, > of strata from the Upper Rotliegend Unit to the Bunter Unit, thus experiencing maximum thermal subsidence from the Late Permian to the Middle Triassic. This rapid burial of sediments lead to subsidence rates of 220 m per million years due to the drastic increase in crustal load. Another important influence of this subsidence is due to the thermal relaxation of the lithospheric magmatic inflation, thus allowing the basin to deepen with the accumulation of the sediment.
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The Madagascar Plate or Madagascar block was once attached to the Gondwana supercontinent and later the Indo-Australian Plate. Rifting in the Somali Basin began at the end of the Carboniferous 300 million years ago, as a part of the Karoo rift system. The initiation of Gondwana breakup, and transform faulting along the Davie Fracture Zone, occurred in the Toarcian (about 182 million years ago) following the eruption of the Bouvet (Karoo) mantle plume. At this time East Gondwana, comprising the Antarctic, Madagascar, Indian, and Australian plates, began to separate from the African Plate.
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MSN Encarta World Atlas. Lake Nyos fills a roughly circular maar in the Oku Volcanic Field, an explosion crater caused when a lava flow interacted violently with groundwater. The maar is believed to have formed in an eruption a maximum of 12,000 years ago, and is 1,800 m (5,900 ft) across and 208 m (682 ft) deep. The area has been volcanically active for millions of years—after South America and Africa were split apart by plate tectonics about 110 million years ago, West Africa also experienced rifting, although to a lesser degree.
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At the onset of the Neoproterozoic the supercontinent Rodinia, which had assembled during the late Mesoproterozoic, straddled the equator. During the Tonian, rifting commenced which broke Rodinia into a number of individual land masses. Possibly as a consequence of the low-latitude position of most continents, several large-scale glacial events occurred during the Neoproterozoic Era including the Sturtian and Marinoan glaciations of the Cryogenian Period. These glaciations are believed to have been so severe that there were ice sheets at the equator—a state known as the "Snowball Earth".
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The metamorphic crystalline basement rock underlying the continental shelf in the Norwegian Sea is related to the ancient continent Baltica, which now forms the stable East European Craton. The sequence of events in the Mid-Norwegian Shelf is perhaps most relevant to the geological history of the Norwegian Sea. Early rifts began in the late Paleozoic between what is now Norway and Greenland during the time of the Caledonian orogeny. Rifting seemingly continued through the Carboniferous, Permian and into the Mesozoic, but subsequent tectonic activity and thick overlying sediment complicates the record.
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The rocks deformed during the Thomson Orogeny, referred to as the Thomson Orogen, underlie most of western and central Queensland in Australia. The rocks are mostly rich in quartz and metasedimentary, overlain by younger Mesozoic rocks and the Devonian backarc basin sediments of the Adavale Basin. Detrital zircon dating of Thomson Orogen rocks indicates ages between 510 and 495 million years ago, spanning the Cambrian to the Devonian. In the northern part of the Thomson Orogen, rifting in the late Neoproterozoic is recorded in the lower metamorphic rocks of the Anakie Province.
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In other words, orogeny is only a phase in the existence of an orogen. Five characteristics of the orogenic cycle are listed by For example, the Caledonian Orogeny refers to a series of tectonic events due to the continental collision of Laurentia with Eastern Avalonia and other former fragments of Gondwana in the Early Paleozoic. The Caledonian Orogen resulted from these events and various others that are part of its peculiar orogenic cycle.However, this orogen was superimposed by rifting orogeny at a later time to result in various extents of reworking.
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The activity during the Cretaceous implies that rifting in the North Atlantic was already underway at that time. At that time, the Rockall Trough was at least deep. Xenoliths found in volcanic rocks indicate that at Anton Dohrn volcanic activity involved interactions between magma and sediments, resulting in phreatomagmatic eruptions that could have dispersed volcanic ash in the region. This volcanic ash erupted by Anton Dohrn may be the source of post- Cenomanian bentonites of the British Isles but the age and composition of the bentonites do not support this theory.
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99(B4), pp. 17,791-17,804. This volcanic spreading may initiate further structural deformation in the form of thrust faults along the volcano's distal flanks, pervasive grabens and normal faults across the edifice, and catastrophic flank failure (sector collapse). Mathematical analysis shows that volcanic spreading operates on volcanoes at a wide range of scales and is theoretically similar to the larger-scale rifting that occurs at mid-ocean ridges (divergent plate boundaries). Thus, in this view, the distinction between tectonic plate, spreading volcano, and rift is nebulous, all being part of the same geodynamic system.
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The bent lithosphere to the west of the Ouachita mountains caused a bowl-shaped depression to form, known as a foreland basin, preserving the Mississippian sediments of the Barnett Shale and other Paleozoic sediments; these sediments mostly formed before the Pangeic collision. Significant deposits of hydrocarbons such as natural gas have economic importance as is seen in formations like the Barnett Shale. Pangea started to break up during the Triassic ≈225Ma. Rifting affected regions which became the central Atlantic (between North America and Africa) and the Gulf of Mexico at about the same time.
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Tectonic forces were not strong enough to continue to separate the two sides of the continental rift; when the rifting stopped, the lava cooled and the heavy crust sank and was filled with sediment. During recent glaciations, a large amount of the basalt and sandstone, which erode much more easily than granite, was removed by the glaciers. This formed the rough, rugged shoreline on the North Shore today. As the glaciers retreated, they left behind eroded igneous material, much of which covers the rocky beaches on the North Shore.
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The Late Paleocene to the Early Eocene (55 Ma) saw rift basin formation in the Fuegan Andes which led to crustal extension: the first sign of separation between the two continents and the formation of the South Scotia Sea and South Scotia Ridge. Spreading in the West Scotia Sea led to the further lengthening of the North Scotia Ridge and South Georgia moving further east. Spreading in the West Scotia Sea finally led to the rifting of the South Orkney microcontinent from the tip of the Antarctic Peninsula. This event initiated the South Scotia Ridge.
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The second stage of rifting is characterized by the deactivation of large boundary faults, the development of internal fault segments, and the concentration of magmatic activity towards the rifts. Today, the narrow rift segments of the East African Rift system form zones of localized strain. These rifts are the result of the actions of numerous normal faults which are typical of all tectonic rift zones. As aforementioned, voluminous magmatism and continental flood basalts characterize some of the rift segments, while other segments, such as the Western branch, have only very small volumes of volcanic rock.
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The Pennsylvanian Period marked the beginning of geological processes that would shape the Permian Basin into what we see today. Rifting events during the Cambrian Period (early Paleozoic) left fault zones in the region. This fault zones acted as planes of weakness for faulting that was later initiated by the Ouachita Orogeny. These fault zones caused the Tobosa Basin to be transformed, due to tectonic activity, into the Permian Reef Complex, which comprises three parts: the Central Basin Platform, which is encircled by faults, and the Midland and Delaware Basins on either side.
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The older rocks of the terrane rest in the Precambrian with younger Cambrian rocks resting unconformably upon them. The Precambrian rocks are noted to be calc-alkaline plutonic intrusions dated to approximately 700-600 Ma (Phase 1 to Phase 2 Neoproterozoic). These have associated (younger) volcanics that dominate the overlying sedimentary rocks that date between 570 and 560 Ma. The signatures of the rocks are interpreted as having an intra-plate geochemical signature that may be attributed to arc- rifting. The diachronous formations of the bedded Uriconian and Coomb Volcanic Formation.
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It is an extinct volcano dating to the Neoproterozoic and is approximately 704 million years old (+/- 4 million years) as dated using the U-Pb zircon crystal geochronology method. It is a unit of the Robertson River Igneous Suite and is located within the Blue Ridge anticlinorium. This volcanic formation was a result of crustal extensional rifting of the eastern Laurentian margin of the supercontinent Rodinia. This was the beginning of a chain of events that ultimately gave birth to the precursor Atlantic, the Iapetus Ocean at 550 Ma during the Ediacaran–Cambrian transition.
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The Worcester Basin or Worcester Graben is a sedimentary basin in central England, filled with mainly Permian and Triassic rocks. It trends roughly north-south and lies between the East Malverns Fault in the west and the Inkberrow Fault in the east. It forms part of a series of Permo-Triassic basins that stretch north-south across England, including the Cheshire Basin and the East Irish Sea Basin. These basins resulted from a regional rifting event that affected parts of North-West Europe, eastern North America and East Greenland.
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The Colorado Basin () is a sedimentary basin located in northeastern Argentina. The basin stretches across an area of approximately , of which onshore in the southern Buenos Aires Province and the easternmost Río Negro Province extending offshore in the South Atlantic Ocean. The basin comprises a sedimentary succession dating from the Permian (pre-rift stage) and Early Cretaceous (rift stage) to the Quaternary, representing the passive margin tectonic phase of the basin history. The Mesozoic rifting in the basin resulted from the break-up of Pangea and the formation of the South Atlantic.
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These lava compositions were formed by fractionation of primary alkali basalt magma in crustal reservoirs. A region of continental rifting, such as the Northern Cordilleran Volcanic Province, would support the development of high-level reservoirs of sufficient size and thermal capacity to sustain prolonged fractionation. Map of the Anahim Volcanic Belt The Anahim Volcanic Belt extends from coastal British Columbia across the Coast Mountains into the Interior Plateau. Its western end is defined by alkaline intrusive and comagmatic volcanic rocks of the Bella Bella-King Island complex, exposed in fjords and islands of the western Coast Mountains.
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Several theories have been proposed about the biogeography of the spinosaurids. Since Suchomimus was more closely related to Baryonyx (from Europe) than to Spinosaurus—although that genus also lived in Africa—the distribution of spinosaurids cannot be explained as vicariance resulting from continental rifting. Sereno and colleagues proposed that spinosaurids were initially distributed across the supercontinent Pangea, but split with the opening of the Tethys Sea. Spinosaurines would then have evolved in the south (Africa and South America: in Gondwana) and baryonychines in the north (Europe: in Laurasia), with Suchomimus the result of a single north-to-south dispersal event.
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Later on, the presence of basaltic lava flows indicate a tectonic setting related to basaltic volcanism as the volcanic clasts were derived from the underlying lava and transported by rivers from Gondwana land. The interbedding layers of fluvial sediments and basaltic lava bands imply that there was repeated occurrence of basaltic eruption and erosion and sedimentation of fluvial deposits alternatively. These events were probably caused by breaking up and rifting of Gondwanaland during the Late Jurassic to Early Cretaceous. The whole sequence of Upper Gondwanas (including both the Taltung and Amile Formations) represents non- marine deposition.
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The breakup of the Arabian-Nubian Shield began about 35 Ma with the development of the Afar plume. Activity at the plume created the Ethiopia- Yemen Continental Flood Basalts, and exposed the shield to hot mantle material from below, leading to the onset of rifting some time before 28 Ma. A divergent plate boundary developed, dividing the shield into the Arabian Plate and the Somali Plate. As the plates separated, water from the Indian Ocean filled the newly created basin, resulting in the Gulf of Aden. The spreading center has formed a mid-ocean ridge called the Aden Ridge.
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One of the three models for the thinning and rifting of the continental crust of the South China Sea is initiated by Java and Sumatra subduction causing extrusion and slab roll back along the margin. The stresses from these were experienced in the South China Sea and together they caused the southward extension of the South China Sea. This model indicates subduction to the south of Borneo near Java and Sumatra but not subduction of Borneo or beneath Borneo. This is unlikely to have caused South China Sea spreading singlehandedly but probably contributed to the forces involved.
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When the eastern Palaeo-Tethys closed 250–230 Mya, a series of Asian blocks – Sibumasu, Indochina, South China, Qiantang, and Lhasa – formed a separate southern Asian continent. This continent collided 240–220 Mya with a northern continent – North China, Qinling, Qilian, Qaidam, Alex, and Tarim – along the Central China orogen to form a combined East Asian continent. The northern margins of the northern continent collided with Baltica and Siberia 310–250 Ma, and thus the formation of the East Asian continent marked Pangaea at its greatest extent. By this time, the rifting of western Pangaea had already begun.
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The Niger Delta Basin is an extensional rift basin where rifting occurred from the Late Jurassic to the Late Cretaceous. Cretaceous fracture zones, expressed as trenches and ridges, control the tectonic framework of the delta and separate the margin into individual sub-basins, which form the boundary faults of the Cretaceous Benue- Abakaliki trough. The Niger Delta Basin is the youngest and most southern sub- basin (located at the southwest boundary) in the Benue-Abakaliki trough. The Benue-Abakaliki trough represents a failed arm of a rift triple junction associated with the opening of the South Atlantic.
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This outpouring of lava coincided with uplifting of the Southern African portion of Gondwana, and the formation of rift valleys along what were to become the sea borders of the subcontinent. As these rift valleys widened they became flooded to form the proto-Indian and Southern Atlantic Oceans, as Gondwana fragmented into today's separate continents of South America, Africa, Antarctica, Australia, India, Madagascar and Arabia. In close association with this rifting, a second episode of basalt eruption occurred along the border with Mozambique to form the Lebombo Mountains. A layer of lava more than 4800 m thick was violently extruded at this time.
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The archipelago was once part of the supercontinent of Gondwana and detached during the Miocene epoch, in the same set of rifting events that opened the Gulf of Aden to its northwest. The archipelago consists of the main island of Socotra (), the three smaller islands of Abd al Kuri, Samhah and Darsa, as well as small rock outcrops like Ka'l Fir'awn and Sābūnīyah that are uninhabitable by humans but important for seabirds. The main island has three geographical terrains: the narrow coastal plains, a limestone plateau with karst topography and the Hajhir Mountains. The mountains rise to .
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The geology of Malawi formed on extremely ancient crystalline basement rock, which was metamorphosed and intruded by igneous rocks during several orogeny mountain building events in the past one billion years. The rocks of the Karoo Supergroup and newer sedimentary units deposited across much of Malawi in the last 251 million years, in connection with a large rift basin on the supercontinent Gondwana and the more recent rifting that has created the East African Rift, which holds Lake Malawi. The country has extensive mineral reserves, many of them poorly understand or not exploited, including coal, vermiculite, rare earth elements and bauxite.
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Geologically, Gabon is primarily ancient Archean and Paleoproterozoic igneous and metamorphic basement rock, belonging to the stable continental crust of the Congo Craton, a remnant section of extremely old continental crust. Some formations are more than two billion years old. Ancient rock units are overlain by marine carbonate, lacustrine and continental sedimentary rocks as well as unconsolidated sediments and soils that formed in the last 2.5 million years of the Quaternary. The rifting apart of the supercontinent Pangaea created rift basins that filled with sediments and formed the hydrocarbons which are now a keystone of the Gabonese economy.
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Rifting started about 200 Ma eventually forming the Atlantic Ocean. Along the Cabot Trail between the park headquarters at Ingonish Beach and Ingonish, a 402 Ma old Early Devonian granodiorite is exposed, the Cameron Brook Pluton, while the Keltic Lodge, on Middle Head, sits on a 493 Ma old Early Ordovician granite and a 550 Ma old Neoproterozoic diorite. The beach in front of Freshwater Lake is a classic shingle beach, a barrier beach with boulders well rounded and polished from wave action. Glacial debris is evident along the trail at the north end of the lake.
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The relatively thin crust and short lifespan of the Aegir Ridge is anomalous given its proximity to the Iceland hotspot. Mantle hotspots deliver warm, actively-upwelling material to mid-ocean ridges, increasing mantle melting and crustal production. Likely, the stresses associated with plate tectonics and the mechanical structure of the lithosphere created a situation in which spreading at the Kolbeinsey Ridge was energetically favorable to spreading at the Aegir Ridge. As the Kolbeinsey Ridge began rifting, hotspot material would then draw out of the Aegir Ridge and flow preferentially towards the Kolbeinsey Ridge, leading to the ultimate extinction of the spreading center.
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As the Atlantic and Arctic oceans opened during the Mesozoic and into the Cenozoic, the Arctic Region underwent several stages of rifting, sedimentation, and magmatism. Dolerites collected from Svalbard and elsewhere in the Arctic are mafic intra-plate tholeiites characteristic of HALIP, which indicated that the LIP formed during the opening of the Arctic Ocean around 148–70 Ma. Seismic and magnetic analyses of the seafloor produced ages of 118–83 Ma. The HALIP is widely thought to have originated from a mantle plume, and the igneous activity of the province often tracked along a similar path as the Icelandic hotspot.
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The rifting in the Basquo-Cantabrian, North Pyrenean, and Subpyrenean Basin had stopped and basin inversion set in; tensional faults were then being used as thrusts. This first rather weak compressional phase with very low shortening rates (less than 0.5 mm/year) lasted till the end of the Thanetian. On the Spanish side of the orogen, the first thrust sheets were emplaced (Upper Pedraforca, Bóixols, and Turbón thrust sheets). In Ilerdian and Cuisian times (Paleocene/Eocene boundary, Thanetian/Ypresian, about 55 million years ago), the Pyrenees underwent very strong compression in the upper crust, bringing about the orogen's actual zonation and structural organisation.
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The Kutch District of modern-day Gujarat lies 3–400 km from the plate boundary between the Indian Plate and the Eurasian Plate, but the current tectonics is still governed by the effects of the continuing continental collision along this boundary. During the break-up of Gondwana in the Jurassic period, this area was affected by rifting with a roughly west–east trend. During the collision with Eurasia the area has undergone shortening, involving both reactivation of the original rift faults and development of new low-angle thrust faults. The related folding has formed a series of ranges, particularly in central Kutch.
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Much attention has been given to remotely triggered earthquakes since the 1992 Landers earthquake in southern California. The Dead Sea fault system runs from the Red Sea north to a triple junction in south-central Turkey and consists of a main fault and several secondary faults. The fault system is at its widest and deepest in the gulf where a transition from proto-oceanic rifting to transform faulting occurs. Moving northward through Lebanon and Syria, where the DST is known as the Yammouneh fault, the trace follows a restraining bend and splits into several strands that include the Serghaya and Rachaya faults.
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NASA satellite image showing Tennessee's Sequatchie Valley and the Cumberland Plateau (image source: Aqua satellite, MODIS sensor). Sequatchie Valley is a relatively long and narrow valley in the U.S. state of Tennessee and, in some definitions, Alabama. It is generally considered to be part of the Cumberland Plateau region of the Appalachian Mountains; it was probably formed by erosion of a compression anticline, rather than rifting process as had been formerly theorized. The Sequatchie River drains the valley in Tennessee, flowing south to southwest from the southern part of Cumberland County, Tennessee to the Tennessee River near the Alabama border.
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Huge slopes made of fractured basalt scree are visible beneath many of the ledges of Talcott Mountain; they are particularly evident along the base of the lower tier of cliffs west of Heublein Tower. The basalt cliffs are the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa. These basalt floods of lava happened over a period of 20 million years. Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows, which eventually lithified into sedimentary rock.
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The Otway Basin is a northwest trending sedimentary basin located along the southern coast of Australia. The basin covers an area of 150,000 square kilometers and spans from southeastern South Australia to southwestern Victoria, with 80% lying offshore in water depths ranging from 50-3,000 meters. Otway represents a passive margin rift basin and is one of a series of basins located along the Australian Southern Rift System. The basin dates from the late Jurassic to late Cretaceous periods and formed by multi-stage rifting during the breakup of Gondwana and the separation of the Antarctic and Australian plates.
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Retrieved on 2007-10-18 The formation is a rare alkaline-suite that formed as a result of submarine rifting during the Paleoproterozoic period.Volcanology and geochemistry of the Bravo Lake Formation, Baffin Island, Nunavut. Retrieved on 2007-10-18 The Bravo Lake Formation is surprisingly undeformed by the Himalayan-scale forming event during the Trans- Hudsonian orogeny. The stratigraphy of the Bravo Lake Formation starts with a basic section of iron-oxide rich sandstones, psammites, and semi-pelites which cover a series of deformed pillow lavas which expand in viscosity towards the west, and volcanic/clastic deposits and ultramafic sills.
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The Pelotas Basin formed with the rifting of Brazil and Africa splitting the Río de la Plata Craton from the Kalahari Craton. The break-up of Pangaea characterised the start of formation of the Pelotas Basin in the South Atlantic, forming at the same time the Namibia Basin in Africa. The basins of the South Atlantic margin started forming in the Early Cretaceous with the break-up of Gondwana, the southern part of the former supercontinent Pangea. This tectonic movement resulted in a sequence of rift basins bordering the present-day South Atlantic on the Brazilian and southwestern African sides.
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Iceland is located above the Mid-Atlantic Ridge. Some scientists believe the hotspot beneath Iceland could have contributed to the rifting of the supercontinent Pangaea and the subsequent formation of the North Atlantic Ocean. Igneous rocks which arose from this hotspot have been found on both sides of the Mid-Atlantic Ridge, which originated 57–53 million years ago ("Ma"), around the time North America and Eurasia separated and sea floor spreading began in the Northeast Atlantic. Geologists can determine plate motion relative to the Icelandic hotspot by examining igneous rocks throughout the Northern Atlantic region.
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Around 200 million years ago in the Triassic, Pangea began to break apart, forming rift valleys. During this period, the Connecticut River Valley began opening as a regional rift, but became a "failed rift" as rifting continued further to the east opening the proto-Atlantic Ocean. Large mafic basalt dikes and flows extruded in the valley, forming the east–west line of the Holyoke Range. The 80-mile-long Hartford Basin and the smaller Deerfield Basin which formed during this time period experience movement along the Connecticut Valley border fault, which bounds the eastern margin of both basins.
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The Blue Nile basin originated in an area of Neoproterozoic rocks aged about 750 Ma that had become a peneplain, possibly during the Paleozoic era (540–250 MaMa = Million years ago). The basin was formed due to rifting during the Mesozoic era (250–66 Ma). Between the Triassic and early Jurassic, about 300 m of fluvial sediments were deposited by rivers and streams. During the Jurassic (200–145 Ma) the basin was twice covered by an arm of the Indian Ocean for extended periods, creating a lower limestone sediment 450 m thick and an upper limestone sediment 400 m thick.
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The tectonic structures in the Niger Delta Basin are typical of an extensional rift system, but the added shale diapirism due to loading makes this basin unique. The main method of deformation is gravitational collapse of the basin, although the older faulting and deformation in the basin are related to the continental breakup and rifting of the African plate and South American plates. The overall basin is divided into a few different zones due to its tectonic structure. There is an extensional zone, which lies on the continental shelf, that is caused by the thickened crust.
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Drilling in the Parana Basin and sampling of dikes around São Paulo revealed that the Serra Geral basalts and Kaoko basalts in Namibia both formed at the same time—121 million years ago—marking the beginning of the rifting open of the South Atlantic. Elsewhere, flood basalts and hypabyssal rocks from the Mesozoic mark the opening of the ocean in Maranha in the north. The Pernambuco Shear Zone in the northeast reactivated during the breakup of the supercontinent Pangea in the Cretaceous. In the late Cretaceous, kimberlite, carbonatite, olivine melilitite and tuffaceous diatreme intruded the Sao Francisco Craton.ikcabstracts.com/index.
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The Andes orogeny took place during the Cenozoic. Rifting and strike-slip faulting in weak Cretaceous magmatic arc rocks was reactivated with the collision of the South America and Nazca plates around nine million years ago. Uplift began around seven million years ago in the Sierra Pampeanas, a group of reverse fault-bounded Precambrian and Paleozoic rocks in the central Andes foreland basin. To the south, in Tierra del Fuego, turbidites accumulated in the basins formed in the late Cretaceous, producing the Paleocene Rio Claro Group, the Eocene La Despedida Group and the Oligocene Cabo Domingo Group.
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Continued spreading in the Norwegian Sea eventually separated Greenland from Eurasia, resulting in the creation of the Greenland Plate and the South Greenland Triple Junction. By this time spreading within Baffin Bay and the Labrador Sea had slowed and became oblique, eventually ceasing between 45 and 36 million years ago. The final phase of rifting was marked by continental extension in the mid-Tertiary. It breached the North American continent and reached the Arctic Ocean, resulting in the formation of the Parry and Nares submarine rift valleys, the Queen Elizabeth Islands and the Queen Elizabeth Islands Subplate.
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Hydrocarbons of the Kapuni Field are trapped by the Kapuni Anticline, in the hanging wall of the east-dipping Manaia Fault, a reverse fault in the Eastern Mobile Belt. The Kapuni Anticline is asymmetric, doubly-plunging, and approximately 18 km long and 8 km wide. The Manaia Fault initially developed as a normal fault bounding the Manaia Graben during Cretaceous to Early Eocene rifting associated with the opening of the Tasman Sea. Dextral transpression associated with the Hikurangi Subduction System caused fault reactivation and basin inversion during the Eocene and Miocene, resulting in the development of the Kapuni Anticline.
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Rifting in the GLTZ began about at the end of the Algoman orogeny. The orogeny affected adjacent regions of northern Minnesota and Ontario in the Superior province as well as the Slave and the eastern part of the Nain province, a far wider region of influence than in subsequent orogenies. It is the earliest datable orogeny in North America and brought the Archean Eon to a close. The end of the Archean Eon marks a major change in the development of the Earth's crust: the crust was essentially formed and achieved thicknesses of about under the continents.
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The Gulf of California Rift Zone (GCRZ) is the northernmost extension of the East Pacific Rise which extends some from the mouth of the Gulf of California to the southern terminus of the San Andreas Fault at the Salton Sink. The GCRZ is an incipient rift zone akin to the Red Sea Rift. In the GCRZ continental crust originally associated with the North American Plate has been pulled apart by tectonic forces and is being replaced by newly formed oceanic crust and seafloor spreading. The rifting has resulted in the transfer of the Baja California Peninsula to the Pacific Plate.
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Rocks in the area, especially within the latter sub-basin were folded during the Variscan Orogeny to form the Ribblesdale Fold Belt which is aligned broadly southwest - northeast. Further south is the Rossendale Basin.BGS 1:50,000 geological map memoir for sheet 59 Lancaster, p130-140 In the west of the county, the West Lancashire basin is in effect a landward extension of the East Irish Sea Basin. The area is threaded by numerous broadly north-south aligned normal faults thought to have been active during Permo-Triassic times and perhaps later, in association with early rifting of the Atlantic Ocean.
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Precambrian rocks from the Iberian Peninsula suggest it too probably formed part of core Gondwana before its detachment as an orocline in the Variscan orogeny close to the Carboniferous–Permian boundary. South-east Asia is made of Gondwanan and Cathaysian continental fragments that were assembled during the Mid-Palaeozoic and Cenozoic. This process can be divided into three phases of rifting along Gondwana's northern margin: firstly, in the Devonian, North and South China, together with Tarim and Quidam (north-western China) rifted, opening the Palaeo-Tethys behind them. These terranes accreted to Asia during Late Devonian and Permian.
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Domal uplift can occur contemporaneously with incipient subsidence in different segments of a proto-rift structure. The evolution of the Brent Delta System of the northern North Sea follows this model. Deposition of the Brent Group has been coupled with the growth and erosion of a mid-North Sea dome, as well as with non-dome related tectonics along the northern North Sea rift margins. As domal uplift related to incipient rifting is commonly associated with subsidence in its vicinity, erosional products tend to accumulate in associated depositional basins that may be a proto-rift, as with the Brent Delta system.
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Spreading also began in the northernmost part of the IBM arc about 25 Ma and propagated south to form the Shikoku Basin. Parece Vela and Shikoku basin spreading systems met about 20 Ma and the combined Parece Vela Basin-Shikioku Basin continued widening until about 15 Ma, ultimately producing Earth's largest back-arc basin. The arc was disrupted during rifting but began to build again as a distinct magmatic system once seafloor spreading began. Arc volcanism, especially explosive volcanism, waned during much of this episode, with a resurgence beginning about 20 Ma in the south and about 17 Ma in the north.
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The Agulhas Bank relative to the Agulhas Ridge, Basin, and Plateau As Gondwana formed 500 mya, a rift appeared which eventually developed into the Agulhas Sea. This sea filled with sediments that were to become the Cape Supergroup, which subsequently were folded into the Cape Fold Belt. The oldest rock found along the coastline of the Agulhas Bank are eugeosynclinal sediments of the up to thick Kaaimans Group deposited during continental rifting some 900 million years ago (Mya). The proto-South Atlantic closed during the Saldanian orogeny to form part of the supercontinent Gondwana (700-600 Mya).
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119-143, 1988. The geologic history of the Takutu Graben is characterized by one phase of volcanic activity and three depositional phases of sedimentary rocks. Rifting (due to divergent tectonic plate movements) occurred in a lake or delta environment in the Late Triassic to Early Jurassic periods, between 200 million and one hundred and fifty million years ago."The Takutu Graben," The Guyana Chronicle Online, June 2, 2012 Starting around 66,000 years ago, sea level rise and more humid conditions created flooded zones north of the confluence of the Rio Negro and the Solimões River, in what is now Roraima.
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The supercontinent Pangaea was rifting during the Triassic--especially late in the period--but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangea--which separated New Jersey from Morocco--are of Late Triassic age; in the U.S., these thick sediments comprise the Newark Supergroup. Because of the limited shoreline of one super- continental mass, Triassic marine deposits are globally relatively rare; despite their prominence in Western Europe, where the Triassic was first studied. In North America, for example, marine deposits are limited to a few exposures in the west.
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Huerta, A.D., and D.L. Harry (2012) Wilson cycles, tectonic inheritance, and rifting of the North American Gulf of Mexico continental margin. Geosphere. 8(1):GES00725.1, first published on March 6, 2012, The Gulf of Mexico basin is roughly oval and is approximately wide and floored by sedimentary rocks and recent sediments. It is connected to part of the Atlantic Ocean through the Florida Straits between the U.S. and Cuba, and with the Caribbean Sea via the Yucatán Channel between Mexico and Cuba. With the narrow connection to the Atlantic, the Gulf experiences very small tidal ranges.
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More extensive dating of Avalonian rocks both in southern Britain and Maritime Canada has allowed Avalonian subduction to be refined into several stages. Gibbons & Hõrak (1996) grouped the Stanner-Hanter Complex with the Malverns Complex placing both within Avalonian Event 1, the early arc-construction phase, which has been dated at 677Ma. Implicit in this interpretation, however, is the assumption that the Stanner-Hanter rocks have a calc-alkaline composition. Slightly older dolerites and gabbros in the Avalonian of Newfoundland have a more primitive oceanic affinity related to the rifting and formation of primitive oceanic crust.
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It is located within the Australian marine park known as the South-west Corner Marine Park. The Naturaliste Plateau formed during the Early Cretaceous 136 Ma when Australia and India broke up and during the Late Cretaceous 83 Ma when Australia and Antarctica broke up. Lavas and intrusive rocks on the plateau flanks have ages of between 132-128 Ma. The eastern flank of the plateau slopes relatively gently, while the other three flanks are relatively steep. The southern flank formed during the Australia-Antarctica break-up, the other flanks during the rifting between India and Australia.
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Geothermal heating peaks in crust about to be rifted; and since warmer rocks are less dense, the crustal rocks rise up relative to their surroundings. This rising creates areas of higher altitude, where the air is cooler and ice is less likely to melt with changes in season, and it may explain the evidence of abundant glaciation in the Ediacaran period. The eventual rifting of the continents created new oceans and seafloor spreading, which produces warmer, less dense oceanic lithosphere. Due to its lower density, hot oceanic lithosphere will not lie as deep as old, cool oceanic lithosphere.
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An early and widely cited paper by (drawing on features of the fairly new theory of plate tectonics) exemplifies the off-shore or "seamount" type of models. It featured a set of radiometrically determined (K-Ar and 40Ar-39Ar) ages that were younger in the center (for the Grays River volcanics) and older at the ends. This dihedrally symmetric age progression strongly suggested the pattern seen at spreading ridges, where the older rock is carried away on both sides from where the new rock erupts. Duncan considered five models (but none involving rifting or ridge subduction),.
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There was hardly a land rush into such marginal land, but the uplands were slowly settled by farmers throughout most of the 18th century and organized into townships. Then in the early 1800s better land opened up in Western New York and the Northwest Territory. The hilltown agricultural population went into a long decline and fields began reverting to forest. The Connecticut River Valley is an ancient downfaulted graben or rift valley that formed during the Mesozoic Era when rifting developed in the Pangaea supercontinent to separate North America from Europe and South America from Africa.
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The Okch'ŏn Zone likely formed in mid-Cambrian times with faulting, interpreted from olistolith limestone breccia. By contrast to the Chŏsun Supergroup, the Okch'ŏn Supergroup crops out in the central Okch'on-T'aebaeksan Zone with thick sequences of metasedimentary and metavolcanic rocks. Some geologists have interpreted the supergroup as a series of nappe formations that took shape in a Cambrian intracratonic basin. Above the volcanic and sedimentary sequence in the middle part of the supergroup are jumbled rocks formed from submarine debris flows during rifting and contain granite, gneiss, quartzite, limestone, mudstone and basic volcanic rock fragments.
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Map showing hypothetical extent of Doggerland (c. 8,000 BC), which provided a land bridge between Great Britain and continental Europe North Sea from De Koog, Texel island The North Sea between and , as Central Europe became dry land Shallow epicontinental seas like the current North Sea have since long existed on the European continental shelf. The rifting that formed the northern part of the Atlantic Ocean during the Jurassic and Cretaceous periods, from about , caused tectonic uplift in the British Isles. Since then, a shallow sea has almost continuously existed between the uplands of the Fennoscandian Shield and the British Isles.
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The Basque-Cantabrian Basin is a large sedimentary basin on thinned continental crust that lies onshore and offshore along the southern margin of the Bay of Biscay on the north coast of Spain. Rifting broke up Jurassic carbonate "ramps," leading to the erosion of some of these carbonate units. When the basin first formed, it was partly separated from the neighboring Pyrenean basin by the Landes high-ground, although this feature later got underthrusted and buried by Cretaceous sediments offshore. The faulted offshore Biscay synclinorium is believed to be an extension of the onshore Pyrenean fault zone, by way of the Leiza fault.
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"KT events in India: impact, rifting, volcanism and dinosaur extinction," in Novas & Molnar, eds., Proceedings of the Gondwanan Dinosaur Symposium, Brisbane, Memoirs of the Queensland Museum, 39(3): iv + 489–731 : 489-532 However, this claim was rejected by Galton and Upchurch (2004), who noted that the skull, tooth and plate of Dravidosaurus are certainly not plesiosaurian as illustrated. Galton and Ayyasami (2017) reaffirmed the stegosaurian classification of Dravidosaurus, claiming the remains do not look like plesiosaurian pelvic and hindlimb elements. They announced that stegosaurian remains from the Dravidosaurus type locality are under study by one of the original describers of Dravidosaurus.
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Most of the evidence suggests the increase of volcanic activity was the main cause of the extinction. As a result of the rifting of the super continent Pangea, there was an increase in widespread volcanic activity which released large amounts of carbon dioxide. At the end of the Triassic period, massive eruptions occurred along the rift zone, known as the Central Atlantic Magmatic Province, for about 500,000 years. These intense eruptions were classified as flood basalt eruptions, which are a type of large scale volcanic activity that releases a huge volume of lava in addition to sulfur dioxide and carbon dioxide.
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Several theories have been proposed about the biogeography of the spinosaurids. Since Suchomimus was more closely related to Baryonyx (from Europe) than to Spinosaurus—although that genus also lived in Africa—the distribution of spinosaurids cannot be explained as vicariance resulting from continental rifting. Sereno and colleagues proposed that spinosaurids were initially distributed across the supercontinent Pangea, but split with the opening of the Tethys Sea. Spinosaurines would then have evolved in the south (Africa and South America: in Gondwana) and baryonychines in the north (Europe: in Laurasia), with Suchomimus the result of a single north-to-south dispersal event.
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The most important event in the eastern Palatinate's geological development was the rifting and downfaulting relative to the surrounding low mountains of the Upper Rhine Plain, whose onset was some 65,000,000 years ago in the Lower Tertiary and which has lasted until today. Before the mountains spread an area that was over time scored by the Eckbach and Floßbach. During the ice ages, there were gradual solifluction on the slopes and also wind abrasion in great parts of Europe. These processes led to a transformation of the original surface relief in whose wake a floodplain with embanked or eroded terraces formed.
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One proposed model theorizes that the Farallon plate underwent subduction and imbrication beneath the North American plate to form the Challis Arc. Another model suggests that intracontinental rifting and igneous activity between the Pacific and North American plates formed the Challis arc. By definition, a volcanic arc is formed via subduction, so the Challis Arc's naming as a volcanic arc is a matter of debate among geologists. The current limited availability of historical geochemical data prevents any of the proposed theories from being confirmed or falsified, so there is still no consensus on the Challis Arc's formation.
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Arc volcanism and extension occurred as the Neo-Tethys Ocean subducted under the southern margin of Laurasia during the Mesozoic. Uplift and compressional deformation took place as the Neotethys continued to close. Seismic surveys indicate that rifting began in the Western Black Sea in the Barremian and Aptian followed by the formation of oceanic crust 20 million years later in the Santonian. Since its initiation, compressional tectonic environments led to subsidence in the basin, interspersed with extensional phases resulting in large-scale volcanism and numerous orogenies, causing the uplift of the Greater Caucasus, Pontides, Southern Crimean Peninsula and Balkanides mountain ranges.
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The geology of the DFW Metroplex consists of gently tilted sediments of mostly Cretaceous age, which also obscures a much older geologic record. Sediments older than Cretaceous can only be found at the surface in the extreme western part of the DFW Metroplex, in the area around Weatherford, Texas. Ancient folded mountains formed by the Ouachita orogeny existed in the eastern part of the Metroplex 300 million years ago. These ancient mountains were reduced by erosion and rifting associated with the opening of the Gulf of Mexico in the Jurassic and then were buried beneath younger Cretaceous sediments.
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The Atlantic ocean and the Arctic ocean are good examples of active, growing oceanic basins, whereas the Mediterranean Sea is shrinking. The Pacific Ocean is also an active, shrinking oceanic basin, even though it has both spreading ridge and oceanic trenches. Perhaps the best example of an inactive oceanic basin is the Gulf of Mexico, which formed in Jurassic times and has been doing nothing but collecting sediments since then.Huerta, Audrey D. and Harry, Dennis L. (2012) "Wilson cycles, tectonic inheritance, and rifting of the North American Gulf of Mexico continental margin" Geosphere 8(2): pp.
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By contrast, the much smaller southwestern rift has been quiet since a rifting episode in 1974, and to date, has not been involved in the current eruptive cycle at all. The southwestern rift zone's extremity is also underwater, although its submarine length is more limited. The southwestern rift zone also lacks a well-defined ridge line or a large number of pit craters, evidence that it is also geologically less active than the eastern rift zone. A prominent structure on Kīlauea's southern flank is the Hilina fault system, a highly active fault slipping vertically an average of per year along the system.
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Lamprophyres are usually associated with voluminous granodiorite intrusive episodes.Rock, N.M.S., 1991, Lamprophyres, Blackie, Glasgow, UK They occur as marginal facies to some granites, though usually as dikes and sills marginal to and crosscutting the granites and diorites.Jackson, T. A., Lewis, J. F., Scot, P. W., Manning, P. A. S., 1998, The Petrology of Lamprophyre Dykes in the Above Rocks Granitoid, Jamaica: Evidence of rifting above a subduction zone during the early Tertiary. Caribbean Journal of Science, vol. 34, no. 1-2, pp. 1-11, 1998. In other districts where granites are abundant no rocks of this class are known.
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West Antarctic Rift system in the Ross Sea Mount Melbourne is part of the McMurdo Volcanic Group and together with Mount Erebus one of its active volcanoes. This volcanic group is one of the largest alkaline volcanic provinces in the world, comparable with that of the East African Rift, and is subdivided into the Melbourne, the Hallett and the Erebus volcanic provinces. The volcanic group consists of large shield volcanoes mainly near the coasts, stratovolcanoes and monogenetic volcanoes which formed parallel to the Transantarctic Mountains. Volcanic activity of the McMurdo Volcanic Group is tied to continental rifting and commenced during the Oligocene.
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The main driving forces of the growth faults are the deferential sediments load and the low density layers - evaporites or over-pressured shale - that are formed during or right after the rifting process. Growth faults are located mainly within passive margin sedimentary wedges where tectonic forces have minimum or no effect. These passive margins receive millions of tons of sediments every year which are concentrated on the continental shelf below base level and above areas where the water velocity is no longer supporting the particles weight. This zone is called depositional center (depocenter for short) and has higher sediments load.
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The formation comprises several lithologies, from sandstone, conglomerates and shales to marls, siltstones, limestones and lignite and gypsum beds and ranges between in thickness. The Tremp Formation was deposited in a continental to marginally marine fluvial-lacustrine environment characterized by estuarine to deltaic settings. The Tremp Basin evolved into a sedimentary depression with the break-up of Pangea and the spreading of the North American and Eurasian Plates in the Early Jurassic. Rifting between Africa and Europe in the Early Cretaceous created the isolated Iberian microplate, where the Tremp Basin was located in the northeastern corner in a back-arc basin tectonic regime.
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The origin of the Tuzo Wilson Seamounts is not without controversy. Some geologists theorize that the Tuzo Wilson Seamounts are linked with a hotspot because lava at the Tuzo Wilson Seamounts are fresh, glassy pillow basalts of recent age, as expected if these seamounts are located above or close to a hotspot south of the Haida Gwaii archipelago.J. Tuzo Wilson Knolls: Canadian hotspot Retrieved on 2007-08-13Origin of Igneous Rocks: The Isotopic Evidence Retrieved on 2008-03-08 Others prefer rifting as the cause of volcanism because the seamounts are close to the Explorer spreading center. No theory is close to airtight.
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When subduction was active, it triggered the formation of andesitic rocks known as "Andesite of Sierra Santa Lucía" in the area around La Reforma. These are the local manifestations of Comondú Group volcanics from activity occurring 24 to 13 million years ago. The last subduction-related volcanism, producing Santa Rosalía dacite, was between 13 and 12 million years ago. Subsequently, rifting in the Santa Rosalía Basin was accompanied by volcanism which laid down the basalts- basaltic andesite of the Boleo Formation (11-9 million years ago), the El Morro tuff (9-8 million years ago) and the Cerro San Lucas unit (9.5–7.7 million years ago).
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Geologists have interpreted the metasedimentary belts between the East Sahara Craton and the Red Sea fold and thrust belt as a rifting zone, related to the formation of an ocean in the Neoproterozoic. The Jebel Rahib Belt, situated in the northwest, contains deformed basic and ultrabasic igneous rocks and thick layers of carbonaceous metasediments, formed at the time of the Pan-African orogeny. This time constraint for deformation and low-grade metamorphism comes from granitoids formed after the orogeny, dated to 570 million years ago. Dense, mafic oceanic crust formed in the Jebel Rahib rift as evidenced by an ophiolite assemblage that includes ultramafic rocks, pyroxenite, gabbro, chert and pillow lava.
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All the units where vinculated to the Transdanubian Range Unit, where the Sachrang Formation and the Úrkút Manganese shared the paleogeographic evolution present on the southern near land margin, influenced by a continuous process of Rifting present on the Tethys Ocean. On the Hettangian the vinculated central European platforms drowned and where affected by Sinemurian-Pliensbachian tensional tectonic events along with marine sedimentation, reoriented by the emersion of horsts on the Úrkút area. The Pliensbachian basin had near 200 m depth, and the presence of slope environments, tectonically influenced basins are indicated on locations such as the Hiertlaz Limestone.LA VÖRÖS, A. T. T. I. (1991).
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As part of the Comoro Islands chain in the Mozambique Channel, the geology of Mayotte is virtually the same as the geology of the Comoros, the rest of the island chain which is independent of France. The island resulted from the rifting of Madagascar away from Africa as well as "hotspot" mantle plume activity, and is also impacted by seismicity and deformation associated with the East African Rift. However, because Mayotte is a part of France its geology is significantly more researched than that of other islands in the chain. Mayotte is a primarily volcanic island rising steeply from the bed of the ocean to a height of on Mont Bénara.
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The geology of Somalia is built on more than 700 million year old igneous and metamorphic crystalline basement rock, which outcrops at some places in northern Somalia. These ancient units are covered in thick layers of sedimentary rock formed in the last 200 million years and influenced by the rifting apart of the Somali Plate and the Arabian Plate. The geology of Somaliland, the de facto independent country in northern Somalia, is to some degree better studied than that of Somalia as a whole. Instability related to the Somali Civil War and previous political upheaval has limited geologic research in places while heightening the importance of groundwater resources for vulnerable populations.
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Volcanic rocks erupted on the Markagunt Plateau range from alkali basalt over basalt and basaltic andesite to andesite and latite, and define calc-alkaline and tholeiitic suites which appear to become more silicic over time. Phenocrysts include clinopyroxene, olivine and plagioclase, with not all minerals present in all flows. Volcanic rocks at Markagunt Plateau are unusual for the common occurrence of subalkaline volcanics; most other recent volcanic centres in the Basin and Range Province have produced alkali basalts. Mixing between crustal melts and primitive magmas may explain this tendency, while the presence of tholeiite may indicate the occurrence of rifting processes in western Utah.
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Since the Sevier and Laramide orogenies occurred at similar times and places, they are sometimes confused. In general the Sevier orogeny defines an older, more western compressional event that took advantage of weak bedding planes in overlying Paleozoic and Mesozoic sedimentary rock. As the crust was shortened, pressure was transferred eastward along the weak sedimentary layers, producing “thin- skinned” thrust faults that generally get younger to the east. In contrast, the Laramide orogeny produced “basement-cored” uplifts that often took advantage of pre-existing faults that formed during rifting in the late Precambrian during the breakup of the supercontinent Rodinia or during the Ancestral Rocky Mountains orogeny.
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The Taylorsville Basin is a half-graben, with the main controlling fault forming the northwestern boundary of the basin. Subsurface data from boreholes and seismic reflection profiles, indicate that the basin was originally a series of smaller half-graben at the time of the deposition of the Doswell Group. The unconformity at the base of the overlying King George Group marks a reorganization of the rift geometry with further extension being accommodated on a single basin-bounding fault zone, giving a simple NW-thickening wedge in this upper interval. The basin was inverted during the Early Jurassic, soon after the rifting stopped, forming NE-trending folds over intrabasinal normal faults.
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About 85 Ma ago the part of the Farallon plate from approximately California to the Gulf of Alaska separated to form the Kula Plate. ; ; ; ; . The period 48-50 Ma (mid-Eocene) is especially interesting as this is when the subducted Kula--Farallon spreading ridge passed below what is now the OWL.. A slightly variant view is that this piece of the Kula plate had broken off to form the Resurrection Plate , so this was actually the Resurrection--Farallon spreading ridge. (The Burke Museum has some nice diagrams of this.) This also marks the onset of the Oregon rotation, possibly with rifting along the OWL,; .
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This distance poses a problem, however, insofar that if it were a fishing village, it is situated far from the shore of the Sea of Galilee. In an attempt to rectify the problem, the following hypotheses have been devised: #Tectonic rifting has uplifted et-Tell (the site is located on the Great African-Syrian Rift fault). #The water level has dropped from increased population usage, and land irrigation. In fact, the excavation of Magdala's harbor has proven that the ancient water-level was much higher than it is today.F. D. Troche, “Ancient Fishing Methods and Fishing Grounds in the Lake of Galilee” Palestine Exploration Quarterly, 148,4 (2016) 290-91.
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It also extended the western margin. The Iberian Abyssal Plain, off the west coast of Portugal and Spain, formed 126 Ma. This separated Newfoundland's Grand Banks, with Galicia Bank and Flemish Cap being split at 118 Ma. By Early Cretaceous, 110 Ma rifting occurs on west and north west edges. During the time of the supercontinent Pangea, the Iberian plate was joined to Armorica (Northern France). During the break-up of Pangea, in the early Cretaceous, the Bay of Biscay started opening around 126 Ma and completed by 85 Ma. This created the Biscay Abyssal Plain, and parted the Iberian plate from the Trevelyan Escarpment.
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Even if the bulk of the 1,500 gigatons of carbon was released in a single pulse, further feedbacks would be necessary to produce the observed isotopic excursion. On the other hand, there are suggestions that surges of activity occurred in the later stages of the volcanism and associated continental rifting. Intrusions of hot magma into carbon-rich sediments may have triggered the degassing of isotopically light methane in sufficient volumes to cause global warming and the observed isotope anomaly. This hypothesis is documented by the presence of extensive intrusive sill complexes and thousands of kilometer-sized hydrothermal vent complexes in sedimentary basins on the mid-Norwegian margin and west of Shetland.
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The Perth Basin began forming in the Late Permian during the breakup of Gondwana, as the Australian continental plate began rifting away from the African and Indian continental plates. During the Permian, what is now the Perth Basin was the eastern half of a rift valley that formed as the continental plates were pulled apart. This pulling apart, which continued until the Jurassic, led to the central zone subsiding as a graben allowing the sea to enter with the subsequent deposition of transgressive marine sediments. The Perth Basin architecture is dominated by listric, extensional faulting that formed during sedimentation and controlled the distribution of the sediments.
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Queen Charlotte, Denali and Tintina fault zones The volcanic history of the Northern Cordilleran Volcanic Province presents a record of volcanic activity in northwestern British Columbia, central Yukon and the U.S. state of easternmost Alaska. The volcanic activity lies in the northern part of the Western Cordillera of the Pacific Northwest region of North America. Extensional cracking of the North American Plate in this part of North America has existed for millions of years. Continuation of this continental rifting has fed scores of volcanoes throughout the Northern Cordilleran Volcanic Province over at least the past 20 million years (see Geology of the Pacific Northwest) and occasionally continued into geologically recent times.
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An area of continental rifting, such as the Northern Cordilleran Volcanic Province, would aid the formation of high-level reservoirs of capable size and thermal activity to maintain long- lived fractionation. In the past 15 million years, at least four large volcanoes have formed their way through dense igneous and metamorphic composed bedrock of this part of North America. This includes Hoodoo Mountain, the Mount Edziza volcanic complex, Level Mountain and Heart Peaks, which are primarily located in northwestern British Columbia. Most notable of these is the 7.5 million year old Mount Edziza volcanic complex, which has had more than 20 eruptions in the past 10,000 years.
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The Queen Elizabeth Islands Subplate is a triangular tectonic block of the North American Plate containing the Queen Elizabeth Islands of Northern Canada. It is surrounded on the south and southwest by the Parry Rift Valley, on the east by the Nares Rift Valley and on the north and west by the Kaltag Fault, which form part of the Canadian Arctic Rift System. The Queen Elizabeth Islands Subplate formed in the mid-Tertiary during the final stages of the Eurekan Rifting Episode when a large triangular region became severed from the rest of the North American continent. It consists of a number of smaller subplates that are separated by faults.
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The Thamalakane River is a river located in Botswana, Africa, at the southern end of the Okavango Delta. It has no well defined beginning (spring) and no clear end (delta). It is the result of the Thamalakane fault - which began to form about two million years ago by the geological process of rifting that is currently splitting Africa apart along the East African Rift. When the land between two parallel faults (the Gumare fault and the Kunyere fault) started dropping, the Okavango River's flow was blocked by the Thamalakane fault and it started to fan out and built myriads of water channels - what is now known as the Okavango Delta.
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The result of the 2007-2009 study has found that the Gamburtsev are very old, first forming around a billion years ago when continental drift pushed two plates together to form the super-continent of Rodinia. This early range was eroded above the surface but left a deep cold root, which is visible today in seismic images, reaching down into the Earth's mantle. About 250-100 million years ago, the crust started to pull apart in a series of rifting events close to the east of this old root. A forked rift valley runs along the northern side of the mountains containing lakes Sovetskaya and 90East within it.
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Lau Basin volcanics are mainly andesites and dacites that were erupted 6.4 to 9.0 Ma. Most mafic rocks found are 55% SiO2 basaltic andesites. The whole basin floor is mostly composed of MORB-like rocks, but the westmost 80~120 km of the basin floor contains a mixture of MORB, transitional and arc- like basalts. This western region has a different composition because it was formed by extension and rifting between the Lau and Tonga ridges before seafloor spreading started. The grabens in this region was then filled by fresh magma from a mantle source that is different from the mantle source for CLSC/ELSC.
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During the climax of lithospheric rifting, as the crust is thinned, the Earth's surface subsides and the Moho becomes correspondingly raised. At the same time, the mantle lithosphere becomes thinned, causing a rise of the top of the asthenosphere. This brings high heat flow from the upwelling asthenosphere into the thinning lithosphere, heating the orogenic lithosphere for dehydration melting, typically causing extreme metamorphism at high thermal gradients of greater than 30 °C. The metamorphic products are high to ultrahigh temperature granulites and their associated migmatite and granites in collisional orogens, with possible emplacement of metamorphic core complexes in continental rift zones but oceanic core complexes in spreading ridges.
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The Ruzizi (also sometimes spelled Rusizi) is a river, long, that flows from Lake Kivu to Lake Tanganyika in Central Africa, descending from about to about above sea level over its length. The steepest gradients occur over the first , where hydroelectric dams have been built. Further downstream, the Ruzizi Plain, the floor of the Western Rift Valley, has only gentle hills, and the river flows into Lake Tanganyika through a delta, with one or two small channels splitting off from the main channel. The Ruzizi is a young river, formed about 10,000 years ago when volcanism associated with continental rifting created the Virunga Mountains.
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The lake has seen large fluctuations in its size over the years, due to varying inflow of streams. Currently it is about long and averages about wide, making it about in size.Google Earth accessed 6 February 2007 In 1929 it was only about long, but in 1939 it was about long and wide.Encyclopædia Britannica Online/Lake Rukwa During the early rifting of this part of Africa, the basin of Lake Rukwa may at times have been part of a much larger basin which also included the basins of Lake Tanganyika with Lake Malawi; ancient shorelines suggest a final date of overflow into Lake Tanganyika of 33,000BP.
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Fahrig (1987) proposed that the Mackenzie plume impact resulted in the emplacement of a triple junction that had a large mafic dike swarm on every rift arm. Two of the first arms formed the Poseidon Ocean basin and the third arm failed thus forming an aulacogen. This tectonic setting suggestion can be comparable with the early volcano- tectonic evolution of the Yellowstone hotspot, which developed two arms instead of three, followed by failure of both arms. At the Mackenzie hotspot, rifting is considered to have been passive and to have taken place in the crust above the hotspot that should have been weakened by the Mackenzie plume.
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The basalt samples at Paraná and Etendeka have an age of about 132 Ma, during the Valanginian stage of the Early Cretaceous. Indirectly, the rifting and extension are probably the origin of the Paraná and Etendeka traps and it could be the origin of the Gough and Tristan da Cunha Islands as well, as they are connected by the Walvis Ridge (Gough/Tristan hotspot). The seamounts of the Rio Grande Rise (25°S to 35°S) that go eastwards from the Paraná side are part of this traps system.Brazilian 'Atlantis' found - Geologists have announced the discovery of what has been dubbed the 'Brazilian Atlantis', some 900 miles from Rio.
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In general, pre-Triassic stratigraphy and rifting has been confirmed below the northern North Sea but is poorly known and little conclusive information exists about Devonian and Carboniferous extensional events. While precise dating and the spatial extent of the active stretching are uncertain, recent stratigraphic syntheses suggest syn-rift dates of no younger than Scythian, with a possible initiation during the late or even early Permian. The following middle Triassic to early Jurassic post- rift stage is considerable better known. Subsidence (approximately nine intervals) in the northern North Sea was accompanied by faulting, stepping down from both margins towards the present Viking Graben axis.
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USGS Geologic Map of the Gulf of Mexico The formation of the Gulf of Mexico, an oceanic rift basin located between North America and the Yucatan Block, was preceded by the breakup of the Supercontinent Pangaea in the Late-Triassic, weakening the lithosphere. Rifting between the North and South American plates continued in the Early-Jurassic, approximately 160 million years ago, and formation of the Gulf of Mexico, including subsidence due to crustal thinning, was complete by 140 Ma. Stratigraphy of the basin, which can be split into several regions, includes sediments deposited from the Jurassic through the Holocene, currently totaling a thickness between 15 and 20 kilometers.
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Huge slopes made of fractured basalt talus are visible beneath many of the ledges; they are particularly noticeable beneath Mount Tom, Whiting Peak, and Deadtop along the Mount Tom State Reservation park road, or along Metacomet-Monadnock Trail on the summit crest gazing down. The basalt ridges are the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa. These basalt floods of lava happened over a period of 20 million years. Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows, which eventually lithified into sedimentary rock.
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The mountains are typical of the rolling terrain of the piedmont region of North Carolina, and are somewhat similar in formation to the nearby Caraway Mountains and Uwharrie Mountains. The Cane Creek Mountains may have formed as a part of the larger coastal range that was once the Uwharries, which are thought to have formed as a part of the Alleghenian or Appalachian orogeny 300–350 million years ago during the formation and rifting of Pangaea. This earlier range is thought to have had peaks more than high, which would rival the Himalayas, the Andes, and the Alaska Range. However, erosion has worn this old mountain range down.
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The Dead Sea Transform began to form during the early to mid- Miocene, when there was a change in plate motions and rifting stopped in the Gulf of Suez Rift. The initial phase of northward propagation reached as far as southernmost Lebanon and was followed by a period in the Late Miocene where continuing displacement across the plate boundary was taken up mainly by shortening in the Palmyride fold belt. A total displacement of 64 km has been estimated for this early phase of motion. In the Pliocene the DST propagated northwards once more through Lebanon into northwestern Syria before reaching the East Anatolian Fault.
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' The verneshot theory suggests that mantle plumes may cause heating and the buildup of carbon dioxide gas underneath continental lithosphere. If continental rifting occurs above this location, an explosive release of the built up gas may occur, potentially sending out a column of crust and mantle into a globally dispersive, super-stratospheric trajectory. It is unclear whether such a column could stay coherent through this process, or whether the force of this process would result in it shattering into much smaller pieces before impacting. The pipe through which the magma and gas had travelled would collapse during this process, sending a shockwave at hypersonic velocity that would deform the surrounding craton.
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Therefore, most of the rocks were reworked and highly metamorphosed with changes in minerals and texture. Due to the sparse exposure of pre-Neoarchean rocks, only the tectonic settings of the rocks generated from 2.7 to 1.85 billion years ago (during the Neoarchean and Paleoproterozoic Era) are thought to be understood. These settings include a Large Igneous Province event, mantle plume activity, continental collisions, rifting and subductions of plates. The Jiao-Liao-Ji Belt joined the two small blocks (the Longgang and Langrim blocks) together as the larger Eastern Block, whereas the Trans-North China Orogen shows the assembly of Eastern and Western Blocks, forming the North China Craton.
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The Greater India Basin model is therefore put forward to explain such observation, where the total amount of convergent has actually been dispersed into two separate stages of crustal thickening, i.e. the uplift of the microcontinent (Tibetan Plateau) and the Himalaya orogeny. The subduction and disappearance of the Great Indian Basin oceanic crust beneath the microcontinent reduces the measurable amount of total convergence expressed by crustal shortening at the surface. Paleomagnetic data suggests that the Indian continent had experienced a N-S extension with minimum extension rates of 40–67 mm/y during 118 and 68 Ma. Such extensional rate is comparable to typical records of intracontinental rifting.
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Large modern orogenies often lie on the margins of present-day continents; the Alleghenian (Appalachian), Laramide, and Andean orogenies exemplify this in the Americas. Older inactive orogenies, such as the Algoman, Penokean and Antler, are represented by deformed and metamorphosed rocks with sedimentary basins further inland. Areas that are rifting apart, such as mid-ocean ridges and the East African Rift, have mountains due to thermal buoyancy related to the hot mantle underneath them; this thermal buoyancy is known as dynamic topography. In strike-slip orogens, such as the San Andreas Fault, restraining bends result in regions of localized crustal shortening and mountain building without a plate-margin-wide orogeny.
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Heart Peaks is part of the Northern Cordilleran Volcanic Province, a long volcanic chain extending from just north of the city of Prince Rupert in British Columbia through Yukon to the Alaska border. Along this line, the North American Plate has been rupturing. Earth's lithosphere consists of several large tectonic plates, which slowly move towards and away from one another, either converging and subducting or diverging and rifting; volcanoes and earthquakes are generated by these activities. The west coast of North America is the site of plate margins between the large Pacific and North American plates, and also between the smaller Juan de Fuca and Cocos plates.
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The best known defiles are: Meiringspoort, Seweweekspoort, the Tradouw pass, Kogmanskloof, Garcia's pass, the Gourits River gorge (which does not have a road running through it), and Michell's Pass, which is, however, more V-shaped than the others, but impressive nevertheless. In addition several roads and highways crest the mountains over cols, or go through them via tunnels. A number of parallel faults still run roughly parallel with the coast, having formed during the Gondwana rifting when South America and the Falkland Plateau separated from Africa. Patagonia was to the west of Cape Town and the Falkland Islands were to the south during the Jurassic Period prior to separation.
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The Northern Cordilleran Volcanic Province rift The Northern Cordilleran Volcanic Province has been a zone of active volcanism since it began to form 20 million years ago. Unlike other parts of the Pacific Ring of Fire, the Northern Cordilleran Volcanic Province has its origins in continental rifting—an area where the Earth's crust and lithosphere is being pulled apart. This differs from other portions of the Pacific Ring of Fire as it consists largely of volcanic arcs formed by subducting oceanic crust at oceanic trenches along continental margins circling the Pacific Ocean. The continental crust at the Northern Cordilleran Volcanic Province is being stretched at a rate of about per year.
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In 1999, a sequence of north-trending faults were mapped that seem to represent young rifting events parallel with the southwestern boundary of the Northern Cordilleran Volcanic Province. These rift-related faults might have been active as recently as five million years ago and they might have connections with adjacent Miocene and younger volcanic activity in the southern part of the Northern Cordilleran Volcanic Province. In addition, brittle faults with similar north-trending directions might enlarge as far north as the fault next to the western flank of the Mount Edziza volcanic complex. These tectonic events might have helped form the structure the Northern Cordilleran Volcanic Province.
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The second strongest candidate for a plume location is often quoted to be Iceland, but according to opponents of the plume hypothesis its massive nature can be explained by plate tectonic forces along the mid-Atlantic spreading center. Mantle plumes have been suggested as the source for flood basalts. These extremely rapid, large scale eruptions of basaltic magmas have periodically formed continental flood basalt provinces on land and oceanic plateaus in the ocean basins, such as the Deccan Traps, the Siberian Traps the Karoo-Ferrar flood basalts of Gondwana, and the largest known continental flood basalt, the Central Atlantic magmatic province (CAMP). Many continental flood basalt events coincide with continental rifting.
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Farther north, subduction of the Pacific Plate has led to extensive volcanism, including the Coromandel and Taupo Volcanic Zones. Associated rifting and subsidence has produced the Hauraki Graben and more recently the Whakatane Graben and Wanganui Basin. Volcanism on Zealandia has also taken place repeatedly in various parts of the continental fragment before, during and after it rifted away from the supercontinent Gondwana. Although Zealandia has shifted approximately to the northwest with respect to the underlying mantle from the time when it rifted from Antarctica, recurring intracontinental volcanism exhibits magma composition similar to that of volcanoes in previously adjacent parts of Antarctica and Australia.
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Bob White is also a Fellow of St Edmund's College, Cambridge, prior to which he was a student and Research Fellow at Emmanuel College, Cambridge. A Fellow of the Geological Society, and a member of the American Geophysical Union and several other professional bodies; he serves on numerous of their committees. He leads a research group investigating the Earth's dynamic crust. His most cited paper (White & McKenzie 1989) used geophysical evidence in conjunction with models of melt generation beneath rifts to show that the largest and most rapid effusions of volcanic rock on the earth, known as flood basalts, result from continental rifting above mantle plumes.
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Heating reduces the density of the lithosphere and elevates the lower crust and lithosphere. In addition, mantle plumes may heat the lithosphere and cause prodigious igneous activity. Once a mid-oceanic ridge forms and seafloor spreading begins, the original site of rifting is separated into conjugate passive margins (for example, the eastern US and NW African margins were parts of the same rift in early Mesozoic time and are now conjugate margins) and migrates away from the zone of mantle upwelling and heating and cooling begins. The mantle lithosphere below the thinned and faulted continental oceanic transition cools, thickens, increases in density and thus begins to subside.
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The forms of the zones with lower Vs (colors toward red) suggest the hotter structures in the Mantle. The distinguishing fourth map depicts a depth below the 410 km discontinuity where Vs steeps up (getting overall bluer), but it still displays the signature of a plume at the substrate of the East African Rift. In the white box, the Vs vertical profile at 10°N, 40°E illustrates the increase of velocity with depth and the effect of the 410 km discontinuity. The most recent and accepted view is the theory put forth in 2009: that magmatism and plate tectonics have a feedback with one another, controlled by oblique rifting conditions.
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The formation is composed of ignimbrites produced by a series of at least three Quaternary caldera eruptions that culminated in the Valles Caldera eruption 1.256 million years before the present (Mya).Phillips 2004 The Valles Caldera is the type location for resurgent caldera eruptions,Smith and Bailey 1968 and the Bandelier Tuff was one of the earliest recognized ignimbrites.Ross and Smith 1961 The caldera lies on the intersection of the western margin of the Rio Grande Rift and the Jemez Lineament.Aldrich 1986Whitmeyer and Karlstrom 2007 Here magma produced from the fertile rock of an ancient subduction zone has repeatedly found its way to the surface along faults produced by rifting.
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Palisade Head is formed from a rhyolitic lava flow which was extruded some 1.1 billion years ago. During the Mesoproterozoic era of the Precambrian eon, the continent spread apart on the Midcontinent Rift System extending from what is now eastern Lake Superior through Duluth to Kansas; this rifting process stopped before an ocean developed. A flow some 200 feet (60 meters) thick formed extremely hard volcanic rock which resisted a billion years of erosion which cut down surrounding formations. This formed both Palisade Head and Shovel Point, which is within the main part of Tettegouche State Park about two miles (three kilometers) to the east.
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Ptychites studeri ammonoid fossil from Triassic rocks in Bosnia During the Triassic, rifting emplaced igneous rocks, including large plutons up to 50 cubic kilometers in size, made up of gabbro, diorite, granodiorite, granite, albite, syenite and occasionally metamorphosed to greenschist or amphibolite-grade on the sequence of metamorphic facies. True volcanic rocks from the Triassic that erupted onto the surface are less common, mainly basalt, andesite and dacite, transformed into spilite, keratophyre and pyroclastic rocks. Older Triassic rocks and the carbonate platform were covered over by lava. Graywacke, breccia, shale and chert and ophiolite are widespread in the Ophiolite Zone, in northwestern and central Bosnia.
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Little is known of the geodynamics of the opening of the North Atlantic between Greenland and Europe. As the Earth's crust was stretched above the mantle hotspot under stress from plate rifting, fissures opened up along a line from Ireland to the Hebrides and plutonic complexes were formed. Hot magma over 1000 °C surfaced as multiple, successive and extensive lava flows covered over the original landscape, burning forests, filling river valleys, burying hills, to eventually form the Thulean Plateau, which contained various volcanic landforms such as lava fields and volcanoes. There was more than one period of volcanic activity during the NAIP, in between which sea levels rose and fell and erosion took place.
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The lower basement is made of granites, gneisses and schists formed during the Eburnean age, about 2100–2000 Ma. The upper basement extends under part of the arc in Zambia and is mostly made of schists, quartzites and quartz-muscovite schists. The Kibaran orogeny deformed and metamorphosed the upper basement between 1350 Ma and 1100 Ma. The Katanga supergroup sediments are from to thick. Rifting between the Congo and Kalahari cratons around 880 Ma opened two basins, first the Roan rift and then the Nguba rift, both of which gathered sediments. Extension was replaced by compression as the Kalahari and Congo cratons moved back towards each other at the start of the Pan-African orogeny.
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As central Africa entered the Phanerozoic, the current geologic eon in which multicellular plant and animal life is commonplace, sedimentary rocks were deposited in what may have been failed rift valleys. These rocks are mainly found in the Congo Basin, a structural tectonic feature that extends into neighboring Democratic Republic of Congo, formed within the Congo Craton. Because of thick layers of sediment atop the craton in central Africa, remoteness and sparse research from boreholes and seismic lines, the exact origins of many of these sedimentary units remains unclear. Geologists currently interpret many of the sedimentary sequences from the Late Permian into the Triassic as the remains of the Karoo rifting period.
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Uranium ores from Ontario have occasionally yielded yttrium as a byproduct. Well-known minerals containing cerium, and other LREE, include bastnäsite, monazite, allanite, loparite, ancylite, parisite, lanthanite, chevkinite, cerite, stillwellite, britholite, fluocerite, and cerianite. Monazite (marine sands from Brazil, India, or Australia; rock from South Africa), bastnäsite (from Mountain Pass rare earth mine, or several localities in China), and loparite (Kola Peninsula, Russia) have been the principal ores of cerium and the light lanthanides. Enriched deposits of rare-earth elements at the surface of the Earth, carbonatites and pegmatites, are related to alkaline plutonism, an uncommon kind of magmatism that occurs in tectonic settings where there is rifting or that are near subduction zones.
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The Ischigualasto-Villa Unión Basin () is a small sedimentary basin located in the Argentine Northwest, Argentina. It is located in the southwestern part of La Rioja Province and the northeastern part of San Juan Province. The basin borders the Sierras Pampeanas in the east, the western boundary of the basin is formed by the Valle Fértil Fault, bordering the Precordillera, and it is bound in the southeast by the El Alto Fault, separating the basin from the Marayes-El Carrizal Basin. The basin started forming in the Late Permian, with the break-up of Pangea, when extensional tectonics, including rifting, formed several basins in Gondwana; present-day South America, Africa, Antarctica, India and Australia.
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Meeting point of the Haardt and the Upper Rhine Plain The most important event in the Deidesheim area's, and indeed the whole eastern Palatinate's, geological development was the rifting and downfaulting relative to the Haardt of the Upper Rhine Plain, whose onset was some 65,000,000 years ago in the Lower Tertiary and which has lasted until today. The area before the Haardt range was over time scored by brooks that rise in the Palatinate Forest. During the ice ages, there were gradual solifluction on the slopes and also wind abrasion. These processes led to a transformation of the original surface relief in whose wake an alluvial fan with embanked or eroded terraces formed.
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The Pacific Northwest from space The geology of the Pacific Northwest includes the composition (including rock, minerals, and soils), structure, physical properties and the processes that shape the Pacific Northwest region of North America. The region is part of the Ring of Fire: the subduction of the Pacific and Farallon Plates under the North American Plate is responsible for many of the area's scenic features as well as some of its hazards, such as volcanoes, earthquakes, and landslides. The geology of the Pacific Northwest is vast and complex. Most of the region began forming about 200 million years ago as the North American Plate started to drift westward during the rifting of Pangaea.
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This Middle to Late Jurassic rifting that created the Gulf of Mexico basin, the continental crust underlying Louisiana and adjacent areas was stretched and thinned forming the northern edge of Gulf of Mexico. Within the Gulf of Mexico basins, the widespread accumulation of thick Louann salt and other evaporate deposits occurred within a shallow, extremely salty Gulf of Mexico basin on top of thinned continental crust. By the end of the Early Cretaceous, the combination of deposition and subsidence had created the modern morphology of the Gulf of Mexico basin. Exposures of rocks older than Upper Cretaceous are lacking within the borders of Louisiana so that is when the local fossil record began.
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Today, the African Plate is moving over Earth's surface at a speed of 0.292° ± 0.007° per million years, relative to the "average" Earth (NNR-MORVEL56) The African Plate is a major tectonic plate straddling the equator as well as the prime meridian. It includes much of the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges. Between and , the Somali Plate began rifting from the African Plate along the East African Rift. Since the continent of Africa consists of crust from both the African and the Somali plates, some literature refers to the African Plate as the Nubian Plate to distinguish it from the continent as a whole.
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Before the opening of the South Atlantic the São Francisco and Congo cratons were connected by a "cratonic" bridge, the Bahia–Gabon Bridge. The most recent orogenic event on this bridge occurred at 2 Ga, so the connection between São Francisco and Congo must have formed during the Palaeoproterozoic. South of this cratonic bridge the Araçuaí–West Congo orogen evolved in the Neoproterozoic in a sea basin made of oceanic crust, an embayment in the São Francisco–Congo continent. The West Congo Pan- African Belt includes major magmatic events at 1000 and 910 Ma. In the Early Neoproterozoic, the western edge of Congo Craton was the location for the initial rifting of Rodinia before its break-up.
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Pangea began to break up during the Triassic, while Gondwana moved northward taking Antarctica way from the South pole region. Subduction continued along the Pacific margin, and Triassic strata was deposited along the Transantarctic Mountains and the Antarctic Peninsula, including the Trinity Peninsula Group, the Legoupil Formation, and continued deposition of the Victoria Group within the Beacon Supergroup. Gondwana rifting in the Middle Jurassic resulted in voluminous tholeiitic magmtic activity throughout the Transantarctic Mountains and the Antarctic Peninsula. By the Late Jurassic, the peninsula was a narrow magmatic arc, with back-arc basins and fore-arc basins, and represented by the Antarctic Peninsula Volcanic Group, and this activity continued into the Early Cretaceous.
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The Buck Creek basin is a structural basin on the Nechako Plateau in the central Interior of British Columbia, Canada, located north of François Lake between the towns of Houston and Burns Lake. It consists of a faulted depression wide and long, with its base lying to below its rim and the surrounding hills, which are composed of metamorphic rocks. The structure of the Buck Creek basin is rift-related, controlled by a series of northwest- southwest trending strike-slip faults. These faults are related to a period of rifting that trended to the southwest when the Nachako Plateau area was tectonically active during the Late Cretaceous, Eocene and Early Oligocene periods.
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For example, large-scale studies have been conducted for Stable Continental Regions (SCR's), which are defined "as regions of continental crust that have not experienced any major tectonism, magmatism, basement metamorphism or anorogenic intrusion since the early Cretaceous, and no rifting or major extension or transtension since the Paleogene." Finally there is the common question of what is the maximum magnitude for the whole world. Unfortunately, it cannot really be answered, since this earthquake has most likely not happened in the historical record, and we cannot search beyond the earth for analogs. Answers can again be inferred using the finite size of the world's plates (plate tectonics), and the possible limits of the various magnitude scales.
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The Cerro Prieto Fault is a transform fault located in far northern Baja California. It runs between the Cerro Prieto spreading center located southwest of Mexicali, and the Wagner Basin, another spreading center which lies under the Gulf of California. These spreading centers are part of the East Pacific Rise, the northern leg of which has formed the Gulf of California by steadily rifting the Baja California Peninsula away from the mainland of Mexico. Seismic studies indicate a linear trend of hypocenters to the northwest of Cerro Prieto which is interpreted as a continuation of the Cerro Prieto Fault some 45 km to the northwest across the international border about 7 km into southern California.
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The structures present along the Terceira Rift have directions likely associated with pre-rift geometry, as they do not correspond to the current direction of spreading motion, which is approximately N70°. Evidence of pre-rift structures include ancient transform directions of N110°-N125°, reactivating as transtensional fault zones, and N-S directions from former middle-oceanic rift faults, reactivating as left-lateral fault zones. It is important to note other hotspot associated islands do not display these features, and thus, the reactivated structures are most likely a result of the complex tectonic setting associated with the Azores triple junction instability. The above observations may represent earlier stages of development between the rifting of Eurasia and Africa.
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Igneous activity ended around 1.3 billion years ago, with the intrusion of numerous dikes and sills into newly crystallized rhyolite and granite. Although not directly impacting the current boundaries of Missouri, the Midcontinent Rift System formed from 1.2 to one billion years ago as mafic lave erupted in a rift zone spanning Lake Superior through Iowa to Kansas. Laurentia was included in the supercontinent Rodinia from one billion to 541 million years ago and no new rock formation took place in Missouri. Failed rifting of the continent produced the Reelfoot Rift, which extends beneath the Mississippi Embayment to the southeast lowlands of the state and intersects the Missouri Gravity Low, creating the New Madrid Seismic Zone.
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Catskill Escarpment from Olana State Historic Site across Hudson River The geology of New York State is made up of ancient Precambrian crystalline basement rock, forming the Adirondack Mountains and the bedrock of much of the state. These rocks experienced numerous deformations during mountain building events and much of the region was flooded by shallow seas depositing thick sequences of sedimentary rock during the Paleozoic. Fewer rocks have deposited since the Mesozoic as several kilometers of rock have eroded into the continental shelf and Atlantic coastal plain, although volcanic and sedimentary rocks in the Newark Basin are a prominent fossil-bearing feature near New York City from the Mesozoic rifting of the supercontinent Pangea.
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Resolution of July 29, 2004, from the Dirección General de Calidad Ambiental, on the declaration of environmental impact of the project called Parque Eólico Matillas y su Línea Eléctrica de Evacuación . (DOCM No. 154, of August 24, 2004, page 13844). The road from Rillo de Gallo to Pardos, next to the ravine of the Hoz del Río Gallo (Corduente), is proposed as « Global Geosite » (Place of interest Spanish Geological Survey of International Relevance) by the Instituto Geológico y Minero de España for its stratigraphic interest, with the denomination "MZ003: The Permian and Triassic of the Señorío de Molina" within the group of geological contexts «El rifting of Pangea and the Mesozoic successions of the Bética and Iberian mountain ranges'.
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The central Apennines of Italy are dominated by extensional tectonics as a result of either roll-back associated with continuing subduction of the Adriatic Plate or northeastward movement of the Adriatic Plate relative to the Eurasian Plate. The epicentral area of the earthquake lies within the Fucino Basin, an area of active rifting with a Pliocene to recent fill of greater than 1 km of fluvial to lacustrine sediments. Since the Late Pliocene the subsidence has controlled by a set of NW-SE trending, SW-dipping normal faults, including the Marsican Hwy Fault (MHF) and the San Benedetto dei Marsi–Gioia dei Marsi Fault (SBMGF), which bound the northeast side of the basin.
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Tuya Butte is part of the Tuya Volcanic Field, a volcanic field that includes tuyas, postglacial lapilli cones and lava flows and several small shield volcanoes formed during the Pleistocene and Holocene. This in turn is part of the Northern Cordilleran Volcanic Province from Prince Rupert, into the Yukon and the Alaska border caused by rifting of the North American Plate as the Pacific Plate slides northward along the Queen Charlotte Fault. Tuya Butte formed when magma intruded into and melted a vertical pipe in the overlying Cordilleran Ice Sheet. The partially molten mass cooled as a large block, forming the highly developed hyaloclastite and pillow lava with gravity flattening its upper surface.
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Microcontinents from the Cimmerian Superterrane, including Iran, collided with the Eurasian Plate by the late Triassic, while the Neo-Tethys oceanic crust subducated northwards under Eurasia. In the Sinai, the Triassic is preserved with open-ocean carbonate sediments and river sediments, as well as clastic material that spans into the Negev Desert. When the Cimmerian blocks dispersed in the Cretaceous, it caused rifting in the Afro-Arabian Plate area, continuing the expansion of the Palmyra and Levant basins. During the late Cretaceous and the start of the Cenozoic subsidence occurred in the rifted areas and the Levant Basin was part of the Messinian Salinity Crisis which left up to two kilometers of evaporate in the dried out Mediterranean region.
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The Adamastor Ocean was narrow in the north, perhaps similar to the Red Sea, but widened southward. C isotope analyses indicate that the ocean water was strongly stratified and thus that it must have been a closed ocean, similar to the Mediterranean, but probably covered by ice during the Sturtian and Marinoan glaciations. Ocean floor adjacent to the Marmora Terrane (near the Orange River in South Africa) formed 740–580 Ma, dates that represent the first rifting and the first accretion respectively. The Adamastor Ocean closed in three episodes: the Río de la Plata Craton first collided with the Congo Craton, which then collided with the Kalahari Craton, which finally collided with Río de la Plata.
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After the end of the Acadian collision, Northern England was affected by a phase of Early Carboniferous extension, possibly related to the subduction of Rheic Ocean crust beneath Gondwana. Preserved Lower Carbonifeous rocks are found to the west, north and east of the Lake District in the East Irish Sea, Solway and Vale of Eden basins. The sequence consists of limestones of the Carboniferous Limestone Supergroup, overlain by sandstones of the Millstone Grit Group and deltaic sandstones, shales and coals of the Coal Measures Group. The only Permian rocks known from the Lake District area are from the upper part of the sequence and form part of the early syn-rift associated with the mainly Triassic rifting event.
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The basalt (also called traprock) crest of the Metacomet Ridge is the product of a series of massive lava flows hundreds of feet thick that welled up in faults created by the rifting apart of the North American continent from Eurasia and Africa. Essentially, the area now occupied by the Metacomet Ridge is a prehistoric rift valley which was once a branch of (or a parallel of) the major rift to the east that became the Atlantic Ocean. Basalt is a dark colored extrusive volcanic rock. The weathering of iron-bearing minerals within it results in a rusty brown color when exposed to air and water, lending it a distinct reddish or purple–red hue.
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The oldest rocks in the area that now includes Death Valley National Park are extensively metamorphosed by intense heat and pressure and are at least 1700 million years old. These rocks were intruded by a mass of granite 1400 Ma (million years ago) and later uplifted and exposed to nearly 500 million years of erosion. Marine deposition occurred 1200 to 800 Ma, creating thick sequences of conglomerate, mudstone, and carbonate rock topped by stromatolites, and possibly glacial deposits from the hypothesized Snowball Earth event. Rifting thinned huge roughly linear parts of the supercontinent Rodinia enough to allow sea water to invade and divide its landmass into component continents separated by narrow straits.
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Intraplate rifting began in the Triassic, forming massive sedimentary basins between Paleozoic uplands. The North Caspian Depression filled with terrigenous rocks and shallow water carbonates at the edge of the Tethys Ocean, similar to the West Siberian Basin which becomes thicker near the center. The Chu, Turgay, Turan and Kizilkum basins contain sand, clay and coal-bearing shallow water terrigenous sediments and salt deposits two kilometers thick from the Middle Jurassic, up to three kilometers thick from the Cretaceous and one kilometer thick from the Cenozoic. The Triassic was a period of erosion in the Kazakh Uplands and the Zaysan, Alakol, Balkhash and Tengiz basins are all small and filled with Late Triassic through Jurassic lacustrine deposits.
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Kerguelen Plateau Topography Symmetrically across the Indian Ocean ridge and due west of Australia is the Broken Ridge underwater volcanic plateau, which at one time was contiguous with the Kerguelen Plateau before rifting by the mid-ocean ridge. To the north of Broken Ridge is the linear Ninety East Ridge which continues almost due north into the Bay of Bengal and is considered to be a hotspot track. One of the largest igneous provinces (LIPs) in the world, the Kerguelen Plateau covers an area of and rises above the surrounding oceanic basins. Located on the Antarctic Plate, the Kerguelen Plateau is separated from Australia by the Southeast Indian Ridge (SEIR) and from Africa by the Southwest Indian Ridge (SWIR).
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However, not much of a noticeable evidence linking the production of magma in the upper mantle to a possible tectonic system has been stated. The existence of a fault next to the western flank of the Mount Edziza volcanic complex is normally considered to be the prime structural evidence for continental rifting in the Northern Cordilleran Volcanic Province. However, more recent mapping and seismic studies in the Coast Mountains have documented the presence of brittle rift-related faults southwest of the small community of Stewart in northwestern British Columbia. But these faults were in a matter of dispute in 1997 by geologists, stating these faults were last active between 20 and five million years ago.
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After the breakup of Pangaea in the early Mesozoic age, the continents of Africa, South America, Europe and North America began to move away from each other. The breaking up, or rifting, did not take place along one unbroken line; thus, at the southern edge of the European plate the microcontinent Iberia also began to break away from Europe. In the western part of the rift that separated the two landmasses, oceanic crust was formed in what is at present the Gulf of Biscay, while in the eastern part the Valais Ocean was formed. When in the Cretaceous period Africa again began to move towards Europe, the Valais Ocean became sandwiched between the two continents.
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Bathymetric diagram of the Axial Seamount, showing the 1998 eruption and segmentation between the CoAxial, Axial, and Vance segments of the ridge The first documented eruption on the Juan de Fuca Ridge took place on the Cleft segment in 1986 and 1987. Hydrothermal megaplumes indicated a large rifting event, releasing hydrothermal fluids as a result of lavas being extruded from a dike. A majority of the eruptions along the ridge are dike injection events, where molten rock is extruded between cracks in the crust's sheeted dike layer. Typically eruptive events can be predicted, as they are preceded by large earthquake swarms in the region. A significant event took place in June 1993, lasting 24 days at the CoAxial segment.
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Map of the Northern Cordilleran Volcanic Province. Hoodoo Mountain lies on the southern axis of the Northern Cordilleran Volcanic Province, a large line of volcanoes extending from the Alaska-Yukon border to a point near Prince Rupert, British Columbia. The region in turn is part of the Pacific Ring of Fire, a seismically active region that encircles the Pacific Ocean and contains some of the world's most active volcanoes. The Northern Cordilleran Volcanic Province is produced by continental rifting as the Pacific Plate slides northward along the Queen Charlotte Fault, on its way to the Aleutian Trench, which extends along the southern coastline of Alaska and the adjacent waters of northeastern Siberia off the coast of Kamchatka Peninsula.
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The source for the hydrothermal fluid that fuels Magic Mountain probably rises along fracture systems associated with a recent episode of rifting that, in turn, followed a massive outpouring of lava. In contrast, the Northern Explorer Ridge has evolved into a complex compound structure consisting of several rift basins bounded by half-graben and arcuate shaped faults with a superimposed pattern of rhombohedral grabens and horsts. This vigorously venting black smoker of the Main Endeavour hydrothermal field, called Sully, emits jets of particle-laden fluids that create the black smoke. The Endeavour Segment, an active rift zone of the larger Juan de Fuca Ridge on the British Columbia Coast, contains a group of active black smokers called the Endeavour Hydrothermal Vents, located southwest of Vancouver Island.
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The Animikie strata on the Gunflint and Mesabi ranges were far enough away so they escaped this deformation and metamorphism; they contain some of the oldest unmetamorphosed sedimentary deposits in the world. Hotspot causing rifting of tectonic plates About a fourth tectonic event occurred in the Lake Superior region. A hotspot of magma from the earth's mantle beneath present-day Lake Superior rose, causing the crust to dome and break apart. This zone of crustal thinning and fracturing is the Midcontinent Rift System; it extends in a boomerang shape for over from northeastern Kansas northward through Iowa, under the Twin Cities of Minnesota, beneath Lake Superior, and then south through the eastern Upper Peninsula of Michigan and beneath the central Lower Peninsula of Michigan.
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As the crust was being stretched thin and more magma flowed out from below, the center of the rift was continuously subsiding. The vast quantities of rising magma created a vacuum under the crust, the weight of the solidified magma on the surface caused the crust to subside into that vacuum so the edges of the rift tilted toward the center. The rifting stopped after a few million years; one reason could be that the Grenville orogeny stopped the rift process when that collision occurred. Subsidence continued for several million years after the lava flows had ceased; immense volumes of sediments - sand, gravel and mud - were eroded off the barren landscape into the still-sinking basin along the rift axis.
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The Newark Supergroup's lithologies and structure are the classic hallmarks of a rift valley; the fault-blocking illustrates the crustal extension forces in play during the breakup of Pangea during the late Triassic Period. The Appalachian Mountains had already been nearly eroded flat by the end of the period; the uplift and faulting that was the first part of the rifting provided new sources of sediment for the vast thicknesses deposited in the Newark Supergroup; the igneous intrusions are similarly diagnostic of a rift valley. Coarse sediments were deposited near the eastern mountain front, while progressively finer ones were deposited farther west. Evidence suggests the climate at the time was subtropical and rainy, though divided between wet and dry months.
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The Central Lapland Greenstone Belt (CLGB) is a greenstone belt located in the northern part of the Fennoscandian Shield. The region belongs to Lapland, northern Finland. The CLGB is part of a much larger belt of Paleoproterozoic greenstones, a cover of metamorphosed volcanic and sedimentary rocks that cover the Archean basement, the latter which is representative of the Archaean Karelian craton. Deposition of the cover sequence occurred between about 2.5 Ga and 1.8 Ga, thus it preserves information about Earth's history from a period that encompass about 700 Ma. Thus, the CLGB records a prolonged and episodic history of rifting, sedimentation and magmatism before the collision and rift closure at about 1.9 Ga. The collision was related to the amalgamation of the supercontinent Columbia.
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Haruj is not located close to a plate boundary. Rather, volcanism there and in other African volcanic fields which are located on top of crustal domes, has been explained by the presence of hotspots, but in the case of Haruj a mantle plume is considered unlikely. Alternatively, volcanism at Haruj may be the consequence of the intersection of three geological structures of Paleozoic to Tertiary age and melting of the shallow mantle, or of the rifting process of the Sirte Basin. Wau an Namus is sometimes considered to be part of the field, other volcanic fields in Libya are Gharyan, Gabal as Sawada, Gabal Nuqay and Tibesti some of which belong to a long line known as the Tibesti lineament.
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The Circum-Superior Belt was formed 1,884 to 1,870 million years ago when the Superior craton was surrounded by mountain building processes, including the Trans-Hudson, New Quebec and Penokean orogenies. The major Trans-Hudson orogeny had its appearance when the Superior craton collided with the Rae-Hearne and Sask cratons 1,900 to 1,800 million years ago. Massive orogenic belts with a change in horizontal direction are represented by the double promontory structure of the Superior craton that seem to have come from the beginning of a rifting event. The New Quebec orogen, also known as the Labrador Trough, lies at the northeastern portion of the Superior craton and is related to ocean closure and collision with the southeastern portion of the Rae craton.
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In contrast to neighboring Labrador, the island of Newfoundland is largely underlain by younger rocks. The Churchill, Nain, Superior and Grenville Province present in Labrador were all small continents or pieces of continental lithosphere that joined to form sections of the proto-North American continent Laurentia and the broad stable region known as the Canadian Shield. By the end of the Precambrian in the Neoproterozoic, continental crust which had come into existence in the Archean nearly 2.5 billion years had already experienced up to eight supercontinent cycles. In the late Precambrian and Paleozoic, Avalonia (named after the Avalon Peninsula in Newfoundland) formed as a volcanic island arc off the coast of the supercontinents Pannotia which lost land through rifting and became Gondwana.
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Arabia consists of seven countries: Kuwait, Bahrain, Oman, Qatar, Saudi Arabia, the United Arab Emirates, and Yemen.Geopolitics of the World System – Page 337, Saul Bernard Cohen – 2003 The peninsula formed as a result of the rifting of the Red Sea between 56 and 23 million years ago, and is bordered by the Red Sea to the west and southwest, the Persian Gulf to the northeast, the Levant to the north and the Indian Ocean to the southeast. The peninsula plays a critical geopolitical role in the Arab world due to its vast reserves of oil and natural gas. Before the modern era, it was divided into four distinct regions: Red Sea Coast (Tihamah), Central Plateau (Al-Yamama), Indian Ocean Coast (Hadhramaut) and Persian Gulf Coast (Al-Bahrain).
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Huge slopes made of fractured diabase scree are visible beneath many of the ledges of East Rock. These diabase cliffs are the product of lava intrusions hundreds of feet deep that welled up through faults creating sills during the rifting apart of North America from Eurasia and Africa over a period of 20 million years. Erosion and glacial abrasion over the subsequent 200 million years wore away the weaker sedimentary layers, under which the sill had intruded, at a faster rate than the diabase, leaving the abruptly tilted edges of the diabase sheets exposed, creating the distinct linear ridge and dramatic cliff faces visible today.Raymo, Chet and Raymo, Maureen E. Written in Stone: A Geologic History of the Northeastern United States.
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The Indian subcontinent began to collide with Asia circa , since which more than of crust has been absorbed by the Himalayan-Tibetan orogen. During the Cenozoic the orogen resulted in the construction of the Tibetan Plateau between the Tethyan Himalayas in the south and the Kunlun and Qilian mountains in the north. Later, South America was connected to North America via the Isthmus of Panama, cutting off a circulation of warm water and thereby making the Arctic colder, as well as allowing the Great American Interchange. The breakup of Gondwana can be said to continue in eastern Africa at the Afar Triple Junction, which separates the Arabian, Nubian, and Somali plates, resulting in rifting in the Red Sea and East African Rift.
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The transform boundary caused two approximately 22° counterclockwise rotations of the Yucatan Block away from the North American plate. One rotation happened prior to seafloor spreading, and the second rotation happened while the basin spread, creating the current geographical shape of the Gulf of Mexico and the current placement of the Yucatan Peninsula. Simple animation depicting the opening of the Gulf of Mexico The active rifting of the Late-Triassic to Mid- Jurassic, and the stratigraphy which depended strongly on that tectonic development, is followed by a relatively calm tectonic period in the Late- Jurassic. The Late-Jurassic Gulf of Mexico is characterized mostly by prolonged subsidence in the central region, as well as heavy sedimentation around the Florida Platform and Northern Gulf of Mexico.
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Texas is mostly sedimentary rocks, with East Texas underlain by a Cretaceous and younger sequence of sediments, the trace of ancient shorelines east and south until the active continental margin of the Gulf of Mexico is met. This sequence is built atop the subsided crest of the Appalachian Mountains- Ouachita Mountains-Marathon Mountains zone of Pennsylvanian continental collision, which collapsed when rifting in Jurassic time opened the Gulf of Mexico. West from this orogenic crest, which is buried beneath the Dallas- Waco-Austin-San Antonio trend, the sediments are Permian and Triassic in age. Oil is found in the Cretaceous sediments in the east, the Permian sediments in the west, and along the Gulf coast and out on the Texas continental shelf.
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This is due to numerous proxies representing different atmospheric carbon dioxide content. For example, diverse geochemical and paleontological proxies indicate that at the maximum of global warmth the atmospheric carbon dioxide values were at 700–900 ppm while other proxies such as pedogenic (soil building) carbonate and marine boron isotopes indicate large changes of carbon dioxide of over 2,000 ppm over periods of time of less than 1 million years. Sources for this large influx of carbon dioxide could be attributed to volcanic out-gassing due to North Atlantic rifting or oxidation of methane stored in large reservoirs deposited from the PETM event in the sea floor or wetland environments. For contrast, today the carbon dioxide levels are at 400 ppm or 0.04%.
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The phase of rifting was followed by a thermal sag phase and drift stage in the widening of the South Atlantic Ocean. This process led to the deposition of a more than thick succession of clastic and carbonate sediments. One of the largest Brazilian sedimentary basins, it is the site of several recently (2007 and later) discovered giant oil and gas fields, including the first large pre-salt discovery Tupi (8 billion barrels), Júpiter (1.6 billion barrels and 17 tcf of gas), and Libra, with an estimated 8 to 12 billion barrels of recoverable oil. Main source rocks are the lacustrine shales and carbonates of the pre-salt Guaratiba Group and the marine shales of the post-salt Itajaí-Açu Formation.
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The break-up of Gondwana began in the Early Jurassic between West Antarctica, Africa, and Madagascar following the Karoo eruption () centered on southern Africa. Rifting then spread towards Antarctica and seafloor spreading opened what is now the Mozambique Basin, Riiser-Larsen Sea, West Somali Basin, and Weddell Sea during the Late Jurassic. The oldest identified magnetic anomalies (M25–M24) are 154–152 Ma old, but the break-up coincides with the Jurassic Quiet Zone and the oldest anomaly probably is M40 (166 Ma). As Madagascar had been transferred to the African Plate at M10 (130–120 Ma) spreading began between Madagascar and Antarctica — the birth of the Southwest Indian Ridge that still separates the Mozambique Basin from the Riiser-Larsen Sea.
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Greenland separated from North America and the rifting altered direction during the Paleogene, which caused Northern Europe to separate from Greenland. During the Eocene period, the last land bridge across the Atlantic sank. The Alpine Orogeny that occurred about 50 Ma was responsible for the shaping of the London Basin syncline and the Weald anticline to the south. The eastern end of the London Basin merges with the basin of the North Sea, extending on land along the north Kent coast to Reculver and up the east coast of Essex and into Suffolk, where it is overlain by Pleistocene 'Crag' deposits which cover much of eastern Suffolk and Norfolk and are better considered as part of the North Sea basin.
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The Global Volcanism Program reports that the field includes somewhere between 32 and 50 shield volcanoes and cinder cones, with many vents concentrated northwest of the town of Boring. Considered an outlier of the Cascade Range, the Boring Lava Field lies about to the west of the major Cascade crest. It marks one of five volcanic fields along the Quaternary Cascade arc, along with Indian Heaven, Tumalo in Oregon, the Mount Bachelor chain, and Caribou in California. Like the Cascade Range, the Boring field was also generated by the subduction of the oceanic Juan de Fuca tectonic plate under the North American tectonic plate, but it has a different tectonic position, with its eruptive activity more likely related to tectonic rifting throughout the region.
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As extension in the Basin and Range Province slowed by a change in North American Plate movement circa 7 to 8 Million years ago, rifting began on the Gulf of California. Although many of the ranges do share a common geologic history, the Pacific Coast Ranges province is not defined by geology, but rather by geography. Many of the various ranges are composed of distinct forms of rock from many different periods of geological time from the Precambrian in parts of the Little San Bernardino Mountains to 10,000-year-old rock in the Cascade Range. For one example, the Peninsular Ranges, composed of Mesozoic batholitic rock, are geologically extremely different from the San Bernardino Mountains, composed of a mix of Precambrian metamorphic rock and Cenozoic sedimentary rock.
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Mantle plumes and rifting processes are responsible for volcanism in northern Africa; in the case of the Darfur dome volcanic fields such as Jebel Marra, Meidob and Tagabo Hills the most likely explanation is a mantle plume. The location of the volcanism triggered by this plume would be controlled more by the tectonic stress field than by the slow movement of the African Plate, explaining why volcanism began between Jebel Marra and Meidob and then continued in these two fields, which are at opposite sides of the dome. Alternatively, an origin as an intracontinental triple junction has also been proposed but it has been contested on because of a lack of evidence supporting it. Other proposals include the presence of laccoliths.
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This incipient rifting formed as a result of the Pacific Plate sliding northward along the Queen Charlotte Fault, on its way to the Aleutian Trench, which extends along the southern coastline of Alaska and the adjacent waters off the southern coast of the Kamchatka Peninsula. As a result, volcanism in the Northern Cordilleran Volcanic Province is also not related to back-arc basin volcanism. When the stored energy is suddenly released by slippage across the fault at irregular intervals, it can create very large earthquakes, such as the magnitude 8.1 Queen Charlotte Islands earthquake of 1949. As these far- field forces stretch the North American crust, the near surface rocks fracture along steeply dipping faults parallel to the rift zone.
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The Chon Aike Formation forms part of the Chon Aike Province, also known as the Tobífera Series, a large igneous province that covers . The northern part of the formation, Río Pinturas, has been dated to the Late Jurassic (140–160 ), while the western and eastern sections have been dated to 162 ± 11 Ma and 168 ± 2 Ma respectively, indicating Middle Jurassic eruptions. Fossil flora, however, suggests a Middle to Late Jurassic age. (See La Matilde Formation.) During the break-up of Gondwana around 180–165 Ma, the opening of the Weddell Sea lead to extension along the western margin of the South American Plate, resulting in intra-plate volcanism in the Chon Aike area and rifting in the Magallanes Basin.
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The ridge is the product of a huge feeder dike that supplied several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa over a period of 20 million years. Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows and around the dike, which formed sedimentary rocks. The resulting "layer cake" of igneous and sedimentary sheets was later faulted and tilted upward. Subsequent erosion wore away the weaker sedimentary layers a faster rate than the lava layers, leaving the abruptly tilted edges of the lava sheets exposed, creating the distinct linear ridge and dramatic cliff faces visible today along the Metacomet Ridge.
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The breakup of Rodinia (Late Precambrian) is the origin of the original depositional series of the Owambo Basin. The rifting apart of the Congo Craton from the Rodinean shallow sea created a classic pull-apart basin. Pull-apart basins are characterized by faults that create an area of crustal extension, causing uplift at the edges and a sinking of the center, which is infilled by sediment or, in this case, a shallow sea (See Image 3). The deposition of the Nosib Formation (900-750 Ma) is the original deposition from the mass wasting of the newly uplifted edges of the Congo Craton, followed by the Otavi Formation (750-650 Ma), composed of dolomite and limestone from the formation of the shallow sea.
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The Wopmay orogen formed 1882±4 Ma when the Coronation paleocean (named after the Arctic Coronation Gulf) closed between the western margin of the Slave craton and Hottah terrane. The Great Bear magmatic arc remained active 1.88–1.84 Ma while subduction still occurred and still bisects the Hottah terrane north to south. The Coronation margin final closure occurred at 1.74 Ga. The date for the opening of the Coronation Ocean is uncertain, but isotopic studies indicate that initial rifting must be older than about 1.97 Ga. The Hottah arc formed 2.4–2.0 Ga on cryptic crust, probably coeval with sedimentation of Coronation margin. The closure of Coronation Ocean saw an initial phase of westward-directed subduction of oceanic crust beneath the Hottah terrane.
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The tectonic evolution of the Aravalli-Delhi orogenic belt can be divided into four phases: # Bhilwara Gneissic Complex (~ 2,500 Ma) # Aravalli Orogeny (~ 1,800 Ma) # Delhi Orogeny (~ 1,100 Ma) # Post-orogenic evolution (~ 850 – 750 Ma) Two phases of rifting, sedimentation, collision and suturing were documented in the tectonic evolution of the Aravalli-Delhi orogenic belt. During Proterozoic Eon, N-S convergence between the Bundelkhand and Bhandara cratons at the Satpura Mobile Belt, and E-W convergence between the Bundelkhand and Marwar cratons at the Aravalli-Delhi orogenic belt have synchronously occurred in India. This resulted in an overall resultant force of NE-SW convergence of the Aravalli- Delhi orogenic belt, and also led to the arcuate shape of its convergent zone.
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Shelagh Jane Carter (best known as Shelagh Carter, and occasionally referred to as Shelagh Carter-Loewen) is a Canadian director, producer, screenwriter, actress and retired theatre and film professor at the University of Winnipeg, known initially for her short films Night Travellers, Canoe, and Rifting/Blue, and her feature films Passionflower, Before Anything You Say and Into Invisible Light. A Lifetime Member of the Actors Studio and a graduate of the Canadian Film Centre's Directors Lab in Toronto, she is also a recipient of the award, Women in the Director's Chair Career Advancement Module 2010, in collaboration with Women in Film Festival Vancouver, among many other honours. She is a member of the Winnipeg Film Group and chair of their Board.
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The basin started forming in the Early Jurassic, with the break-up of Pangea and the creation of the South Atlantic, when extensional tectonics, including rifting, formed several basins in eastern South America and southwestern Africa. The accommodation space in the Cañadón Asfalto Basin was filled by volcanic, fluvial and lacustrine deposits in various geologic formations, separated by unconformities related to transtensional and transpressional tectonic forces. The Cenozoic evolution of the basin is mainly influenced by the Andean orogeny, producing folding and faulting in the basin. The basin is of paleontological significance as it hosts several fossiliferous stratigraphic units providing many fossils of dinosaurs, turtles, mammals, plesiosaurs, pterosaurs, crocodylomorphs, fish, amphibians and flora in the Mesozoic and mammals, amphibians, fish and flora in the Cenozoic.
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Located in the Portland Basin, the Boring Lava Field consists of monogenetic volcanic cones that appear as hills throughout the area, reaching heights of above their surroundings. The field includes more than 80 small volcanic edifices and lava flows in the Portland–Vancouver metropolitan area, with the possibility of more volcanic deposits buried under sedimentary rock layers. Volcanism in the Boring Lava Field is the product of subduction of the Juan de Fuca oceanic tectonic plate under the North American continental tectonic plate, as well as regional rifting. Powell Butte lies northwest of the Boring Hills, and the surrounding area includes (moving clockwise from the north) other volcanic centers like Green Mountain, Prune Hill, Chamberlain Hill, Devils Rest, Larch Mountain, Pepper Mountain, Kelly Butte, and Mount Tabor.
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Considered an outlier of the Cascade Range, the Boring Lava Field lies about to the west of the major Cascade crest. It marks one of five volcanic fields along the Quaternary Cascade arc, along with Indian Heaven, Tumalo in Oregon, the Mount Bachelor chain, and Caribou in California. Like the Cascade Range, the Boring field was also generated by the subduction of the oceanic Juan de Fuca tectonic plate under the North American tectonic plate, but it has a different tectonic position, with its eruptive activity more likely related to tectonic rifting throughout the region. The Boring Lava Field has erupted material derived from hot mantle magma, and the subducting Juan de Fuca plate may be as shallow as in depth at their location.
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Part of the larger High Arctic Large Igneous Province, it consists of two volcanic formations called the Ellesmere Island Volcanics and Strand Fiord Formation. In the Strand Fiord Formation, flood basalt lavas reach a thickness of at least . Flood basalts of the Sverdrup Basin Magmatic Province are similar to terrestrial flood basalts associated with breakup of continents, indicating the Sverdrup Basin Magmatic Province formed as a result of rifting of the Arctic Ocean and when the large underwater Alpha Ridge was still geologically active. Widespread basalt volcanism occurred between 60.9 and 61.3 million years ago in the northern Labrador Sea, Davis Strait and in southern Baffin Bay on the eastern coast of Nunavut during the Paleocene period when North America and Greenland were being separated from tectonic movements.
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The earliest event recorded in the terrane is the intrusion of the protoliths to the Scourian gneisses at about 3.0-2.7 Ga. Blocks within the Lewisian complex were then juxtaposed by Inverian and Laxfordian deformation from about 2.4-1.7 Ga. At about 1200 Ma, the terrane was affected by extensional tectonics causing rifting and the deposition of the thick coarse clastic sequence of the Torridonian. This was interrupted by a tilting event of unknown origin that caused a hiatus of about 200 Ma, followed by further deposition. At the start of the Cambrian, there was a marine transgression and deposition of shallow marine sandstone and carbonates continuing into the Ordovician. In the Silurian the terrane became involved in the Caledonian continental collision, with the Highland Terrane being thrust over this segment of the Laurentian foreland.
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An alternative theory proposed by Rogers is that if the Anahim hotspot is located under the Wells Gray-Clearwater area, the stress field surrounding the hotspot must precede it by approximately . In 1987, Canadian volcanologist Catherine Hickson revealed that the Wells Gray-Clearwater volcanic field is not part of the Anahim Volcanic Belt, but rather a separate centre that most likely represents an area of lithospheric decompression melting caused by rifting along pre-existing crustal fractures. The Wells Gray-Clearwater volcanic field has since not been considered part of the Anahim Volcanic Belt and the Anahim hotspot is now believed to be in the area of Nazko Cone. The existence of an Anahim hotspot was supported in a detailed Bulletin of Volcanology report by Kuehn et al. (2015).
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Drumheller Channels, part of the Channeled Scablands formed by the Missoula Floods When the rifting of Pangaea, due to the process of plate tectonics, pushed North America away from Europe and Africa and into the Panthalassic Ocean (ancestor to the modern Pacific Ocean), the Pacific Northwest was not part of the continent. As the North American continent moved westward, the Farallon Plate subducted under its western margin. As the plate subducted, it carried along island arcs which were accreted to the North American continent, resulting in the creation of the Pacific Northwest between 150 and 90 million years ago. The general outline of the Columbia Basin was not complete until between 60 and 40 million years ago, but it lay under a large inland sea later subject to uplift.
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Geography of the Contiguous United States in the late Cretaceous period During the Cretaceous, the late-Paleozoic-to-early-Mesozoic supercontinent of Pangaea completed its tectonic breakup into the present-day continents, although their positions were substantially different at the time. As the Atlantic Ocean widened, the convergent-margin mountain building (orogenies) that had begun during the Jurassic continued in the North American Cordillera, as the Nevadan orogeny was followed by the Sevier and Laramide orogenies. Though Gondwana was still intact in the beginning of the Cretaceous, it broke up as South America, Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached to each other); thus, the South Atlantic and Indian Oceans were newly formed. Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels worldwide.
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The East African Rift, where three plates are pulling away from one another: the Arabian Plate and two parts of the African Plate—the Nubian and Somali—which eventually led to the formation of the Lwandle plate as well as other microplates. The Afar Triangle, shaded at the center, is a triple junction that separates the three plates. For many years it was widely accepted that rifting in the East African Rift system, 22–25 million years ago, resulted in the splitting of the African Plate into 2 smaller plates – the Somali Plate and the Nubian Plate. However, most recently, through the application of GPS technology and integration of earthquake data, it was discovered that the rift created three additional “microplates” – the Lwandle Plate, Victoria Plate, and Rovuma Plate.
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Some geologists believe some fundamental change in convection within the Earth's mantle caused the rifting event, while others believe the huge oceanic plate became mechanically unstable as it continued to subduct beneath the Pacific Northwest. The Kula Plate once again continued to subduct beneath the continental margin, supporting the Coast Range Arc. Volcanism began to decline along the length of the arc about 60 million years ago during the early Paleogene period of the Cenozoic era as the rapid northern movement of the Kula Plate became parallel with the Pacific Northwest, creating a transform fault plate boundary similar to the Queen Charlotte Fault. During this passive plate boundary, the Kula Plate began subducting underneath Alaska and southwestern Yukon at the northern end of the arc during the early Eocene period.
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Basal contact of a lava flow section of the Fundy Basin About 250 million years ago during the early Triassic period, Atlantic Canada lay roughly in the middle of a giant continent called Pangaea. This supercontinent began to fracture 220 million years ago when the Earth's lithosphere was being pulled apart from extensional stress, creating a divergent plate boundary known as the Fundy Basin. The focus of the rifting began somewhere between where present-day eastern North America and northwestern Africa were joined. During the formation of the Fundy Basin, volcanic activity never stopped as shown by the going eruption of lava along the Mid-Atlantic Ridge; an underwater volcanic mountain range in the Atlantic Ocean formed as a result of continuous seafloor spreading between eastern North America and northwestern Africa.
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Part of the larger High Arctic Large Igneous Province, it consists of two volcanic formations called the Ellesmere Island Volcanics and Strand Fiord Formation. In the Strand Fiord Formation, flood basalt lavas reach a thickness of at least . Flood basalts of the Sverdrup Basin Magmatic Province are similar to terrestrial flood basalts associated with breakup of continents, indicating the Sverdrup Basin Magmatic Province formed as a result of rifting of the Arctic Ocean and when the large underwater Alpha Ridge was still geologically active. Widespread basalt volcanism occurred between 60.9 and 61.3 million years ago in the northern Labrador Sea, Davis Strait and in southern Baffin Bay on the eastern coast of Nunavut during the Paleocene period when North America and Greenland were being separated by tectonic movements.
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Tephra from northern and southern IBM show that strong compositional differences observed for the modern arc have existed over most of the arc's history, with northern IBM being more depleted and southern IBM being relatively enriched. About 15 Ma, the northernmost IBM began to collide with Honshū, probably as a result of new subduction along the Nankai Trough. A new episode of rifting to form the Mariana Trough back-arc basin began sometime after 10 Ma, with seafloor spreading beginning about 3–4 Ma. Because disruption of the arc is the first stage in forming any back-arc basin, the present Mariana arc volcanoes cannot be older than 3–4 Ma but the Izu-Bonin volcanoes could be as old as ~25 Ma. The Izu interarc rifts began to form about 2 Ma.
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The formation of the Carnegie Ridge and other aseismic ridges in this part of the Pacific started at about 20 Ma when the Galapagos hotspot formed, following the break-up of the Farallon Plate and the formation of the separate Cocos and Nazca Plates. At about 19.5 Ma, the Galapagos Rise spreading center moved so that most of the hotspot magmatism affected the Nazca Plate, forming the combined Carnegie and Malpelo Ridges. At about 14.5 Ma the spreading center jumped south, such that most of the magmatism affected the Cocos Plate and caused the Malpelo Ridge to rift away from the Carnegie Ridge. This stage caused the narrowing of the Carnegie Ridge now seen between 85° W and 87° W. At about 9.5 Ma rifting between the Malpelo and Carnegie Ridges ceased.
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USGS The North German Basin is a passive-active rift basin located in central and west Europe, lying within the southeasternmost portions of the North Sea and the southwestern Baltic Sea and across terrestrial portions of northern Germany, Netherlands, and Poland. The North German Basin is a sub- basin of the Southern Permian Basin, that accounts for a composite of intra- continental basins composed of Permian to Cenozoic sediments, which have accumulated to thicknesses around . The complex evolution of the basin takes place from the Permian to the Cenozoic, and is largely influenced by multiple stages of rifting, subsidence, and salt tectonic events. The North German Basin also accounts for a significant amount of Western Europe's natural gas resources, including one of the world's largest natural gas reservoir, the Groningen gas field.
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The initiation of the Northern German Basin took place in the Late Carboniferous approximately 295-285 Ma (Million Years Ago) in association collapse of the Variscan Orogeny due to wrenching tectonics in the over-thickened crust in the northern foreland of the Variscan Orogeny. The initiation formed by crustal rifting and wrenching in addition to huge amounts of volcanism(>40,000 km3 ) and magmatism, can only be approximately dated due to the extensive (>250 Ma) poly-phased subsidence of the region. The most evident dating method has been done using SHRIMP (Sensitive High-Resolution Ion Microprobe) Zircon ages, allowing for dating of sediments produced during the magmatic flare-up during the Permian. The wrench tectonics, magmatic inflation, and mantle lithosphere erosion took place gave a regional uplift allowing for an increase in crustal erosion.
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Extension of the Gulf of Aden rift system began in the late Eocene - early Oligocene (~35 Ma ago), caused by the northeast escape of the Arabian plate from the African plate at a rate of ~2 cm/yr, and the development of the Afar plume. Extension eventually gave way to seafloor spreading, first initiated near the Owen transform fault ~18 Ma ago. Seafloor spreading then propagated as far west as the Shukra-El Shiek fault at a rate of ~14 cm/yr ~6 Ma ago rifting propagated west of the Shukra-El Shiek fault until terminating at the Afar plume. The Afar plume is believed to have contributed to the initiation of the Aden ridge, due to the flow of hot mantle material being channeled along the thin lithosphere beneath the Gulf of Aden.
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The break-up of Pangaea characterised the start of formation of the Santos Basin in the South Atlantic, forming at the same time the Kwanza Basin in Africa. The Santos Basin formed with the rifting of Brazil and Africa splitting the Congo Craton from the Araçuaí Belt, shown as a thin brown strip. Schematic diagram of the formation of a passive margin on a rift basin The South Atlantic margin developed on Archean stable cratons consisting of hard and resistant rocks and partly on the Neoproterozoic mobile belts composed of less resistant metamorphic rocks.Clemente, 2013, p.3 The Precambrian basement of the Santos Basin is exposed as the Araçuaí Belt along the Brazilian coast, most notably in the inselbergs of Rio de Janeiro, of which Sugarloaf Mountain is the most iconic.
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Roaring Brook Falls, a short distance from the Robert Frost Trail on Mount Toby Both the Holyoke Range and Mount Toby were formed 200 million years ago between the end of the Triassic period and the beginning of the Jurassic. The Holyoke Range, part of the Metacomet Ridge that extends south to Long Island Sound, are composed of basalt, an extrusive volcanic rock. This basalt ridge is the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa over a period of 20 million years. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending it a distinct reddish appearance.
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The Pan-African orogenies that stabilized the East Antarctic Shield took place in two main zones; a broad region between the Shackleton Mountain Range, caused by the collision with South Africa, and India, and along the Transantarctic Mountains (Ross Orogeny). The Ross Orogen comprises a deformed sequence of Neoproterozoic to Cambrian sediments. These sediments were deposited at a passive margin that likely developed during the rifting of North America from the East Antarctic Shield, and were subsequently deformed and metamorphosed at a low- to medium-grade and intruded by syn- and post-tectonic granitoids. Plutonism and metamorphism commenced at about 550 Ma with peak metamorphism at 540-535 Ma. At this time, two more high-grade Cambrian mobile belts formed in East Antarctica, the Lutzow Holm Belt and the Prydz Belt.
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He prevented the full destructive force of the experiment from being unleashed by removing the Compac/Amita Drive from its socket in the Nirvash, interrupting the transdimensional rifting that would have led to the planet's destruction, but in the process was himself taken bodily into the rift it created; nothing of him or his uniform remained, save the Compac/Amita Drive. He was later declared dead, and a massive monument, now largely unvisited by an uninterested public, was erected in his home town of Bellforest. Later, it is revealed that his state of being was transferred to the Scub Coral along with other human beings, some of whom in normal reality were apparently suffering from the seeming catatonia caused by Despair Sickness. These individuals' consciousness apparently exist in a non-temporal state.
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The Brawley Seismic Zone represents the northernmost extension of the spreading center axis associated with the East Pacific Rise which runs up the axis of the Gulf of California and is in the process of rifting the Baja California Peninsula away from the mainland of Mexico, with significant subsidence taking place at southern California's Salton Sea and at Laguna Salada in Baja California. Other major locations along the axis include the Cerro Prieto spreading center located south of Mexicali, and Wagner Basin (a submarine depression in the Gulf of California). The Salton Buttes on the south shore of the Salton Sea are on the north margin of the Brawley Seismic Zone and are linked to volcanic and geothermal activity within the zone. The Brawley Seismic Zone has been interpreted as an "onshore spreading center" which runs diagonally across the Salton Trough.
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The Lunde Formation occurs in the northern part of a Late Triassic continental basin that covered most of the present North Sea area. Several thousands of meters of fluvial sediments were deposited in this basin during a thermal subsidence phase following Late Permian to Early Triassic rifting. With an approximate width of between present mainland Norway and the Shetland Platform, the continental post-rift basin contains the Teist, Lomvi and Lunde Formations, and lasted throughout the Triassic until the final depositional stages of the overlying latest Triassic to Early Jurassic Statfjord Formation, when the whole area was flooded during a marine transgression from the north and south in late Sinemurian to early Pliensbachian times. The climate during deposition of the Lunde Formation was semiarid and highly seasonal, typical for the contemporary palaeogeographic position at 40-50 degrees North paleolatitude.
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Pilgrims in Mecca Ras al-Jinz, the easternmost point of the Arabian Peninsula Oman Dubai Marina, United Arab Emirates Madinat Jumeirah and Burj Al Arab The Arabian Peninsula is a land mass situated north-east of Africa. Also known as Arabia or the Arabian subcontinent, it is the world's largest peninsula and covers 3,237,500 km2 (1,250,000 mi2). The area is an important part of the Asian continent and plays a critical geopolitical role of the Middle East and Arab World due to its vast reserves of oil and natural gas. The peninsula formed as a result of the rifting of the Red Sea between 56 and 23 million years ago, and is bordered by the Red Sea to the west, the Persian Gulf to the northeast, and the Indian Ocean and Arabian Sea to the southeast.
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Late Triassic (220 Ma) Stratigraphic chart of the Paraná Basin, with the Candelária Formation belonging to the Gondwana II Supersequence The megaregional Paraná Basin, covering an approximate area of in southeastern South America, was in the late Paleozoic and early Mesozoic part of Gondwana, the southern latitude area of Pangea. Before the opening of the South Atlantic, a rifting phase that started in the Jurassic, the basin was connected to the basins of present-day southern Africa. The Candelária Formation forms part of the Gondwana II Supersequence representing the onset of continental deposition in the Paraná Basin. The Triassic paleofauna of the Paraná Basin is correlated with the African faunas of the Omingonde Formation of the Waterberg Basin in Namibia, the Molteno Formation of the Karoo Basin in South Africa and the Fremouw Formation of present-day Antarctica.
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At the beginning of the Mesozoic when Africa and South America started to separate this re-activated again and was involved in formation of the Takutu Graben in the lower Rupununi area and the Guyana- Suriname basin near the coast and offshore. Both these sedimentary basins have oil potential, and in 2015 significant oil was found in a deep water area off Guyana. During the Mesozoic the headwaters of the Upper Orinoco and Rio Branco flowed through the Takutu Graben via the Essequibo either to the current river mouth, to the Corentyne, the Berbice or the Canje Rivers. Tilting associated with rifting of the Atlantic Ocean resulted in complex patterns of river capture, so now the headwaters of the Rio Branco flow to the south via the Amazon, and the headwaters of the Upper Orinoco flow to the west and north.
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Dendi Caldera, a collapsed volcano in the mountain region The Ethiopian Highlands began to rise 75 million years ago, as magma from the Earth's mantle uplifted a broad dome of the ancient rocks of the Arabian- Nubian Shield. The opening of the Great Rift Valley split the dome of the Ethiopian Highlands into three parts; the mountains of the southern Arabian Peninsula are geologically part of the ancient Ethiopian Highlands, separated by the rifting which created the Red Sea and Gulf of Aden and separated Africa from Arabia. Around 30 million years ago, a flood basalt plateau began to form, piling layers upon layers of voluminous fissure-fed basaltic lava flows. Most of the flows were tholeiitic, save for a thin layer of alkali basalts and minor amounts of felsic (high-silica) volcanic rocks, such as rhyolite.
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Most clupeids are marine and Lake Tanganyika was formed by rifting and has never had a connection with sea, the sub-family that the Lake Tanganyika sardine and its relative the Lake Tanganyika Sprat, are members of, the Pellonulinae are common in southern and western Africa, for example Microthrissa royauxi and Potamothrissa acuitirostris in the Congo Basin. Molecular phylogenetic reconstructions indicate that the ancestors of these freshwater Pellonulines colonised West Africa 25–50 million years ago, at the end of a major marine incursion in the region. Pellonuline herring subsequently speciated in an evolutionary radiation in West Africa, spreading across the continent and colonising Lake Tanganyika during its early formation. This shows that while Lake Tanganyika has never been directly connected with the sea, the endemic freshwater clupeids of the lake are descended from fish who radiated out of an ancient marine incursion.
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The southern pivot seems to be largely abandoned, in part because various studies (e.g.: ; ; ) show most of the rotation was post-accretion. These classes of models have been classified as either "accreted" or "rifted," but this is inaccurate as inshore formation can still involve accretion, and all offshore accretion models using a northern pivot imply rifting. Studies of Siletzia's origins have generally focused on accounting for two principal observations: the large paleorotation (described above), and the voluminous output (over 50,000 cubic miles, exceeding the volume of most continental rift zones, and some flood basalt provinces).. Accounting for the observed volumes of basalt requires an enhanced magmatic source, for which most models invoke either the presence of the Yellowstone hotspot, or slab windows.. The latter would have resulted from the subduction of the Farallon—Kula (or possibly Farallon—Resurrection) spreading ridge.
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Towards the south the two lines converge and give place to one great valley (occupied by Lake Nyasa), the southern part of which is less distinctly due to rifting and subsidence than the rest of the system. Farther north the western hollow, known as the Albertine Rift, is occupied for more than half its length by water, forming the Great Lakes of Tanganyika, Kivu, Lake Edward and Lake Albert, the first-named over long and the longest freshwater lake in the world. Associated with these great valleys are a number of volcanic peaks, the greatest of which occur on a meridional line east of the eastern trough. The eastern branch of the East African Rift, contains much smaller lakes, many of them brackish and without outlet, the only one comparable to those of the western trough being Lake Turkana or Basso Norok.
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Verneshots have been proposed as a causal mechanism explaining the statistically unlikely contemporaneous occurrence of continental flood basalts, mass extinctions, and "impact signals" (such as planar deformation features, shocked quartz, and iridium anomalies) traditionally considered definitive evidence of hypervelocity impact events. (First submitted 17 April 2003). For an informal introduction see Professor Jason Phipps Morgan's faculty biography at Cornell University from May 2004: I became interested in the causes of mass-extinctions, in particular worrying about the 'too-many-coincidences' problem that these periods appear to be associated (if we believe what's published in the mainstream literature) with BOTH extremely rare continental flood basalts and continental rifting, and even rarer 'impact signals' commonly presumed to come from large extraterrestrial bolide impacts. Our recently published Verneshot hypothesis is our best guess on how to explain these coincidences in a self-consistent causal manner.
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During his 10-year residence in Albany, Burke produced many seminal papers on continental rifting, hotspots, Caribbean tectonics, and the effects of continent-continent collision in Asia and other places. In 1983, Burke joined the faculty of the University of Houston and also worked as director and associate director of the Lunar and Planetary Institute at NASA in Houston until 1988. In the 1990s and 2000s, in addition to mentoring graduate students and teaching at the University of Houston, he held many visiting professorships at NASA, JPL, UCLA, Carnegie Institute, and the University of Oslo, Norway. From 2003 and until his death in 2018, Kevin Burke worked in close collaboration with Trond H. Torsvik, who was then the head of the Geodynamics research group at the Geological Survey of Norway and later became a professor of geology at the University of Oslo, Norway.
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Aligned northeast to southwest, the Great Glen Fault extends further southwest in a straight line through Loch Linnhe and the Firth of Lorne, and then on into northwestern Ireland, directly through Lough Swilly, Donegal Bay and Clew Bay as the Leannan Fault. To the northeast the fault connects to the Walls Boundary Fault and the associated Melby Fault and Nestings Fault, before becoming obscured by the effects of Mesozoic rifting to the north of Shetland. The fault continues on the North American side of the North Atlantic Ocean, but is no longer part of a contiguous fault, as the complete fault was broken when the Mid-Atlantic Ridge formed 200 million years ago. The North American side of the fault runs through the length of northwestern Newfoundland, Canada, as the Cabot Fault (Long Range Fault) and on into the Gulf of St. Lawrence.
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Kivu is also the name for the entire region surrounding Lake Kivu, including the portions in Rwanda which contain the vast majority of the lake area's population (the contiguous towns of Goma, Democratic Republic of Congo and Gisenyi, Rwanda, with a combined population approaching 1,000,000, form the largest urbanised area in the Lake Kivu area). The area is characterized by lush vegetation and an extended growing season due in part to its high altitude (1500 m or 4900 ft at the lakeshore) and the volcanic nature of its soil. The Kivu region represents the high point of the East African Rift Valley. The lake itself contains a massive amount of carbon dioxide in its depths, and there is some concern that tectonic activity (rifting) and/or volcanic activity might cause a sudden release of this captured carbon dioxide.
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The evolution of Earth's biosphere, atmosphere, and hydrosphere has long been linked to the supercontinent cycle, where the continents aggregate and then drift apart. The Boring Billion saw the evolution of two supercontinents: Columbia (or Nuna) and Rodinia. The supercontinent Columbia formed between 2.0 and 1.7 Ga and remained intact until at least 1.3 Ga. Geological and paleomagnetic evidence suggest that Columbia underwent only minor changes to form the supercontinent Rodinia from 1.1 to 0.9 Ga. Paleogeographic reconstructions suggest that the supercontinent assemblage was located in equatorial and temperate climate zones, and there is little or no evidence for continental fragments in polar regions. Due to the lack of evidence of sediment build-up (on passive margins) which would occur as a result of rifting, the supercontinent probably did not break up, and rather was simply an assemblage of juxtaposed proto-continents and cratons.
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Western Australian Events The assembly of the Archaean Yilgarn and Pilbara cratons of Australia was initiated at ~2200 Ma during the first phases of the Capricorn orogen. The last stages of the 2770–2300 Ma Hamersley Basin on the southern margin of the Pilbara Craton are Palaeoproterozoic and record the last stable submarine-fluviatile environments between the two cratons prior to the rifting, contraction and assembly of the intracratonic ~1800 Ma Ashburton and Blair basins, the 1600–1070 Ma Edmund and Collier basins, the 1840–1620 Ma northern Gascoyne Complex, the 2000–1780 Ma Glenburgh Terrane in the southern Gascoyne Complex and the Errabiddy Shear Zone at the northwestern margin of the Yilgarn Craton. Between approximately 2000–1800 Ma, on the northern margin of the Yilgarn Craton, the c. 1890 Ma Narracoota Volcanics of the Bryah Basin formed in a transverse back-arc rift sag basin during collision.
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They also represent two very different geological processes: the Great Escarpment resulted from rifting, and the tearing apart of the Gondwana super-continent, whereas the Cape Fold Mountains resulted from the collision of tectonic plates, during the assembly of Gondwana, in the same way that the Andes Mountains in South America are being formed today. The Cape Fold Mountains have been re-exposed by erosion of the coastal plain below the Great Escarpment (see "Geological origin", above), after having been covered by sediments originating from an even higher and more extensive range of mountains, comparable to the Himalayas, that developed during the assembly of Gondwana to the south of the present African continent, on the portion of Gondwana called the "Falkland Plateau", the remnants of which are at present located far to the southwest of southern Africa close to southern tip of South America.
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The present day Kalahari landscape—essentially an inland sand sea sitting within an uplifted sedimentary basin—is the result of a variety of interacting tectonic and geomorphological processes that have operated over considerable timescales. The initial development of the Kalahari was closely linked to the evolution of the African landmass following the break-up of the supercontinent Gondwanaland during the Mesozoic. The gradual separation of Africa from present-day Australia, Antarctica, India and South America was associated with progressive heating and rifting of the crust, which led to the uplift of the southern African continental margin in the mid- to Late Cretaceous. The development of this uplifted margin had significant implications for regional fluvial systems; the end product was a dual drainage pattern consisting primarily of short rivers draining directly into the sea off the Great Escarpment and longer rivers draining inland and never reaching the sea.
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The Atlantic Ocean did not open uniformly; rifting began in the north-central Atlantic. The South Atlantic did not open until the Cretaceous when Laurasia started to rotate clockwise and moved northward with North America to the north, and Eurasia to the south. The clockwise motion of Laurasia led much later to the closing of the Tethys Ocean and the widening of the "Sinus Borealis", which later became the Arctic Ocean. Meanwhile, on the other side of Africa and along the adjacent margins of east Africa, Antarctica and Madagascar, new rifts were forming that would lead to the formation of the southwestern Indian Ocean that would open up in the Cretaceous. The second major phase in the break-up of Pangaea began in the Early Cretaceous (150–140 Ma), when the minor supercontinent of Gondwana separated into multiple continents (Africa, South America, India, Antarctica, and Australia).
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Queen Charlotte, Denali and Tintina fault zones The geography of northwestern British Columbia and Yukon, Canada is dominated by volcanoes of the Northern Cordilleran Volcanic Province formed due to continental rifting of the North American Plate. It is the most active volcanic region in Canada. Some of the volcanoes are notable for their eruptions, for instance, Tseax Cone for its catastrophic eruption estimated to have occurred in the 18th century which was responsible for the death of at least 2,000 Nisga'a people from poisonous volcanic gases, the Mount Edziza volcanic complex for at least 20 eruptions throughout the past 10,000 years, and The Volcano (also known as Lava Fork volcano) for the most recent eruption in Canada during 1904. The majority of volcanoes in the Northern Cordilleran Volcanic Province lie in Canada while a very small portion of the volcanic province lies in the U.S. state of Alaska.
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Tapuae-o-Uenuku's summit comprises the uplifted and eroded foundations of an old volcano Older remnants of volcanism are also found in several places around New Zealand. These were generally formed either when New Zealand still formed part of the Gondwana supercontinent, or while Zealandia was rifting away from the rest of Gondwana, although some have been emplaced in their current setting more recently. (New Zealand is the main part of the submerged microcontinent of Zealandia that currently emerges above the sea.) A band of granitic intrusions covering over 10,000 km², the Median Batholith, stretches from Stewart Island through Fiordland, and again through the West Coast and Nelson after interruption by the Alpine Fault. This was produced between 375 and 105 million years ago in the course of subduction-related volcanism in a long mountain range along the Gondwanan coast somewhat like today's Andes.
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Gondwana began to break up in the early Jurassic following the extensive and fast emplacement of the Karoo-Ferrar flood basalts . Before the Karoo plume initiated rifting between Africa and Antarctica, it separated a series of smaller continental blocks from Gondwana's southern, Proto-Pacific margin (along what is now the Transantarctic Mountains): the Antarctic Peninsula, Marie Byrd Land, Zealandia, and Thurston Island; the Falkland Islands and Ellsworth–Whitmore Mountains (in Antarctica) were rotated 90° in opposite directions; and South America south of the Gastre Fault (often referred to as Patagonia) was pushed westward. The history of the Africa- Antarctica break-up can be studied in great detail in the fracture zones and magnetic anomalies flanking the Southwest Indian Ridge. The Madagascar block and the Mascarene Plateau, stretching from the Seychelles to Réunion, were broken off India; elements of this breakup nearly coincide with the Cretaceous–Paleogene extinction event.
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The formation of the Agulhas Passage was initiated by the Gondwana break-up some (Ma) and the rifting of the Somali and Mozambique Basins, an event associated with the formation of the ocean floor in the Weddell Sea 147 Ma. Between the Agulhas Bank and the Agulhas Passage the boundary between the Earth's crust and the mantle (the Moho) ascend from over which is normal for a continent-ocean boundary. The crustal thickness under the Agulhas Passage varies from which is equally normal for oceanic crust. It is possible, however, that volcanic flows from the Agulhas Plateau large igneous province (LIP) added crustal material to the Agulhas Passage (which is 160-120 Ma) during the LIP formation (100-80 Ma) and that the crust under the passage was originally thinner. The sedimentary layers are very thin in the western Agulhas Passage, in places only .
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Some large layered complexes are not related to mantle plumes, or example, the Skaergaard intrusion in Greenland. Here, the large magma volumes which are created by mid-ocean ridge spreading allow the accumulation of large volumes of cumulate rocks. The problem of creating space for such intrusions is easily explained by the extensional tectonics in operation; extensional or listric faults operating at depth can provide a triangular space for keel-shaped or boat-shaped intrusions such as the Great Dyke of Zimbabwe, or the Narndee-Windimurra Complex of Western Australia. It is also possible that what we see as a cratonic margin today were created by the action of a plume event initiating a continental rifting episode; therefore the tectonic setting of most large layered complexes must be carefully weighed in terms of geochemistry and the nature of the host sequence, and in some cases a mixed mechanism cause is possible.
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In testing the model of catastrophic and equilibrium Model (another hypotheses instead of global stratigraphyHansen, Vicki L. "Venus's shield terrain." Geological Society of America Bulletin 117.5-6 (2005): 808-822.) on Venus, it is found that the older regional plains (rp) are embaying only around 3% of the impact craters and the younger lobate plains (pl) are embaying around 33% of the impact crater on Venus. It suggested that there are likely to have been at least two geological periods on Venus: (1) Earlier global volcanic regime stage (Formation of older regional plains), when the high rate of volcanic activities overwrote the marks of impact cratering (2) Later network-rifting and volcanic regime stage (Formation of younger lobate plains), when the intensity of volcanism is reduced and allowed more impact cratering to beleft on the surface. Thus, the studying of crater distribution and randomness may give clues for Venusian geological history.
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The first of Carter's own short films was The Darkling Plain (2002), which was recognized and honoured in cities across Canada, followed by the experimental narrative film Rifting/Blue (2005), the first of several collaborations with writer and University of Winnipeg colleague Deborah Schnitzer, and which won world festival recognition. Her third short, Night Travellers (2007), was a National Screen Institute Drama Prize winner in 2007. In 2008, The Canadian Film Centre in Toronto invited Carter to participate in an exclusive workshop intensive (the Directors Lab, Short Dramatic Film programme) to develop film projects along with a handful of other Canadian professionals; her project was chosen for development by the Centre with $250,000 in production support. With the support of the University of Winnipeg, Carter directed and completed her award-winning 35mm short One Night in the summer of 2009; it screened at several international film festivals.
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The Hunter-Bowen Orogeny was a significant arc accretion event in the Permian and Triassic periods affecting approximately 2,500 km of the Australian continental margin. The Hunter-Bowen Orogeny occurred in two main phases, a Permian accretion of previously formed passive-marginal Devonian and Carboniferous sediments in the Hunter region and mid-west region of what is now New South Wales, separated by rifting, back-arc volcanism and a later Permian to Triassic event resulting in arc accretion and metamorphism during a subduction event. The Hunter-Bowen Orogeny has resulted in the New England Fold Belt, a tectonic accretion of metamorphic terranes and mid-crustal granitoid intrusions, flanked by Permian to Triassic sedimentary basins which were formed distally to the now-eroded orogenic mountain belt. While the Great Dividing Range north of Sydney is a prominent landform, this is more the result of Cenozoic volcanism and crustal uplift since the Jurassic than the result of the original orogenic belt which is essentially mimics.
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3 pp.556–570. Approximately 4.2 million years ago (Ma) the region experienced widespread and significant volcanism, associated with the Gombe basalts in the Koobi Fora formation to the east and with the Lothagam basalts further south; this event created a lake in the center of the basin and apparently established the modern, continuous depositional system of the Turkana Basin. Deposition in the Turkana Basin overall is driven primarily by subsidence, a result of rifting between the Somali and Nubian plates that has created a series of horst and graben structures, and led to approximately 1 km of sedimentary deposits at the center of the basin every 1 million years. Sedimentary records, which become more sparse and discontinuous at greater distance from the basin center, suggest that the basin has alternated between fluvial and lacustrine regimes throughout the Plio-Pleistocene, primarily as a result of continued volcanic activity first to the east, and later to the south of the basin.
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Saharan Metacraton and neighboring areas The craton may have formed during a period of accelerated crustal growth between 3000 Ma and 2000 Ma (Ma: million years ago). The oldest rocks in Egypt date to about 2700 Ma. Rocks in southern Libya and eastern Chad have been dated between 2900 Ma and 2600 Ma. Some geologists date a rifting episode to between 1200 Ma and 950 Ma. The Pan-African orogeny saw the cratons that had formed the Rodinia super- continent come together in a completely new arrangement into the Gondwana super-continent around 500 Ma. The "Pharusian Ocean", which separated the West African craton from the Saharan craton around 800 Ma, began to close about 730 Ma, and about 635 Ma these two cratons collided, with the basement of the Saharan craton undergoing extensive reworking in the process. The Saharan craton may have been decratonized, perhaps oceanized, during the Pan-African event. At the end of this period the craton was extended and rifts appeared.
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The Kenn Plateau, covers around 100,000 km2, an area larger than the Tasmanian landmass. Various islands and reefs, whose origin is thought to be related to the Tasmantid Seamount Chain, lie along the western margin of the Kenn Plateau and include the well known Kenn Reef and Bird and Cato Island. The Kenn Plateau is thought to have formed as a sliver of continental crust, resulting from the rifting and seafloor spreading that occurred between 95 and 52 million years ago, along the eastern Australian margin forming the Tasman and Coral Sea basins The Kenn Reef areas consists of four main reefs which cover an area of approximately 40 km2 looking like a backward facing L-shaped structure (or boot) of 15 km in length, with a maximum width of 8 km along the southern edge. The three southerly reefs (the toe, foot & ankle and shin of the boot) lie upon a common shelf from which the northern (leg) reef is separated from by a deep channel.
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The block was part of Gondwana during at least the Early Paleozoic, but the timing of rifting is very uncertain, with estimates ranging from the Devonian to Early Cretaceous. It is also disputed whether the block had accreted onto the Asian continental margin by the time of the amber deposition. Some members of the flora and fauna have Gondwanan affinities A recent paleomagnetic reconstruction finds that the Burma Terrane formed an island land mass in the Tethys Ocean during the Mid Creaceous at a latitude around 5-10 degrees south of the equator. At Noije Bum, located on a ridge, amber is found within fine grained clastic rocks, typically medium to greyish green in colour, resulting from the constituent grains being black, yellow, grey and light green. The fine grained rocks are primarily fine to very fine grained sandstone, with beds of silt and shale and laterally persistent thin (1–2 mm thick) coal horizons.
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Rifting and hot spot activity in Iceland Craters and lavas from the 13th century, acidic lake from Suðurnes Geothermal Power Station, steam vents and hydrothermal alteration (Reykjanes Volcanic System) Öskjuhlíð Keilir and mountains of the Krýsuvík Volcanic System Keilir subglacial cone, on top of the shield volcano Þráinskjóldur, fissures and faults surround it. Other subglacial volcanoes on Reykjanes Peninsula: Litla Sandfell with tuya Geitafell (Brennisteinsfjöll) behind Eroded partially submarine volcano and boulder beaches at Reykjanestá Shield volcano Þráinskjöldur Krýsuvík volcanic system with high temperature geothermal areas and maars volcanic zones of Iceland fault near the tip of Reykjanes Peninsula The Reykjanes Peninsula (in Icelandic: Reykjanesskagi) in Southwest Iceland is the continuation of the mostly submarine Reykjanes Ridge, a part of the Mid-Atlantic Ridge, on land and reaching from Esja resp. Hengill down to Reykjanestá. G.B.M.Pedersen, P. Grosse: Morphometry of subaerial shield volcanoes and glaciovolcanoes from Reykjanes Peninsula, Iceland: Effects of eruption environment.
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Here magma produced from the fertile rock of an ancient subduction zone has repeatedly found its way to the surface along faults produced by rifting. This has produced a long-lived volcanic field, with the earliest eruptions beginning at least 13 million years ago and continuing almost to the present day, the most recent known eruption being the obsidian of the Banco Bonito flow, dated to 68.3 ± 1.5 thousand years before the present. Most of the volume of the range is composed of pre-caldera basalts, andesites, and dacites of the Keres Group and Polvadera Group, but there are extensive outflow sheets of the Bandelier Tuff and young rhyolites associated with caldera resurgence, all assigned to the Tewa Group. The two most recent caldera-forming eruptions, dated to about 1.62 million and 1.256 million years ago, produced massive ignimbrite deposits known as the Otowi and Tshirege members, respectively, of the Bandelier Tuff.
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The Aravalli Range joins two of the ancient earth's crust segments that make up the greater Indian craton, the Aravalli Craton which is the Marwar segment of earth's crust to the northwest of the Aravalli Range, and the Bundelkand Craton segment of earth's crust to the southeast of the Aravalli Range. Cratons, generally found in the interiors of tectonic plates, are old and stable parts of the continental lithosphere that has remained relatively undeformed during the cycles of merging and rifting of continents. volcanic arc and geological process of undersea subduction during tactonic collusion global convergent boundary of plate margins It consists of two main sequences formed in Proterozoic eon, metasedimentary rock (sedimentary rocks metamorphised under pressure and heat without melting) and metavolcanic rock (metamorphised volcanic rocks) sequences of the Aravalli Supergroup and Delhi Supergroup. These two supergroups rest over the Archean Bhilwara Gneissic Complex basement, which is a gneissic (high-grade metamorphism of sedimentary or igneous rocks) basement formed during the archean eon 4 Ga ago.
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The bulk of Western Australia consists of the extremely old Yilgarn craton and Pilbara craton which merged with the Deccan Plateau of India, Madagascar and the Karoo and Zimbabwe cratons of Southern Africa, in the Archean Eon to form Ur, one of the oldest supercontinents on Earth (3 – 3.2 billion years ago). In May 2017, evidence of the earliest known life on land may have been found in 3.48-billion-year-old geyserite and other related mineral deposits (often found around hot springs and geysers) uncovered in the Pilbara craton. Because the only mountain-building since then has been of the Stirling Range with the rifting from Antarctica, the land is extremely eroded and ancient, with no part of the state above 1,245 metres (4,085 ft) AHD (at Mount Meharry in the Hamersley Range of the Pilbara region). Most of the state is a low plateau with an average elevation of about 400 metres (1,200 ft), very low relief, and no surface runoff.
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In the Late Jurassic and Early Cretaceous, the East Antarctic Shield began to move southward at a faster rate than Africa and South America, resulting in seafloor spreading between the two sub-blocks of Gondwana in the Weddell Sea, Riiser-Larsen Sea, Mosambique and Somali basins. A long phase of extension and rifting took place in the southern Weddell Sea before the onset of seafloor spreading, dated around 147 Ma. During the mid-Cretaceous, seafloor spreading propagated eastward from the Riiser-Larsen Sea to the Enderby basin between East Antarctica and India. At 50 Ma, the inception of rapid northward drift of the Australian plate caused rapid accretion of oceanic crust on the East Antarctic Shield. Relative extension between West Australia and East Antarctica commenced in the Late Cretaceous to Early Tertiary, but oceanic crust between these two plates was formed only between 45-30 Ma in the Adare Trough of the Ross Sea.
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Columbia began to fragment about 1.5–1.35 Ga, associated with continental rifting along the western margin of Laurentia (Belt-Purcell Supergroup), eastern India (Mahanadi and the Godavari), southern margin of Baltica (Telemark Supergroup), southeastern margin of Siberia (Riphean aulacogens), northwestern margin of South Africa (Kalahari Copper Belt), and northern margin of the North China Block (Zhaertai-Bayan Obo Belt). The fragmentation corresponded with widespread anorogenic magmatic activity, forming anorthosite-mangerite-charnockite- granite (AMCG) suites in North America, Baltica, Amazonia, and North China, and continued until the final breakup of the supercontinent at about 1.3–1.2 Ga, marked by the emplacement of the 1.27 Ga Mackenzie and 1.24 Ga Sudbury mafic dyke swarms in North America. Other dyke swarms associated with extensional tectonics and the break-up of Columbia include the Satakunta-Ulvö dyke swarm in Fennoscandia and the Galiwinku dyke swarm in Australia. An area around Georgetown in northern Queensland, Australia, has been suggested to consist of rocks that originally formed part of Nuna 1.7 billion years ago in what is now Northern Canada.
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In the framework of the plume hypothesis, the volcanism was caused by the flow of hot plume material initially beneath thick continental lithosphere and then beneath the lithosphere of the growing ocean basin as rifting proceeded. The exact position of the plume at that time is a matter of disagreement between scientists, as is whether the plume is thought to have ascended from the deep mantle only at that time or whether it is much older and also responsible for the old volcanism in northern Greenland, on Ellesmere Island, and at Alpha Ridge in the Arctic. As the northern Atlantic opened to the east of Greenland during the Eocene, North America and Eurasia drifted apart; the Mid-Atlantic Ridge formed as an oceanic spreading center and a part of the submarine volcanic system of mid-oceanic ridges. The initial plume head may have been several thousand kilometers in diameter, and it erupted volcanic rocks on both sides of the present ocean basin to produce the North Atlantic Igneous Province.
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It formed due to extensional cracking, faulting, and rifting of the North American Plate as the Pacific Plate grinds and slides past the Queen Charlotte Fault, unlike subduction that produces the volcanoes in Japan, the Philippines, and Indonesia. The region has Canada's largest volcanoes, much larger than the minor stratovolcanoes found in the Canadian portion of the Cascade Volcanic Arc. Several eruptions are known to have occurred within the last 400 years. Mount Edziza is a huge volcanic complex that erupted several times in the past several thousand years and has formed several cinder cones and lava flows. The complex comprises the Mount Edziza Plateau, a large volcanic plateau (65 km long and 20 km wide) made of predominantly basaltic lava flows with four large stratovolcanoes built on top of the plateau. The associated lava domes and satellite cones were constructed over the past 7.5 million years during five magmatic cycles beginning with eruption of alkali basalts and ending with felsic and basaltic eruptions as late as 1,340 years ago.
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Pangea in the Permian (~250 Ma). The Colorado Basin experiences glaciations and a marine transgressive phase in the south polar region. Sketch of the paleogeographic situation of South America during the Late Cretaceous and Early Paleogene, roughly 85 to 63 Ma. The Colorado Basin, located north of the North Patagonian Massif in the South Gondwanan Province (grey), is exposed and eroded during the Maastrichtian. The basin started forming in the Middle to Late Jurassic with the break-up of Pangea and the formation of the Southern Atlantic.Geologic Map Hojas 3963-III & IV, 2009, p.42 The main rifting took place in the Early Cretaceous. The pre-rift sequence of the basin comprises the Pennsylvanian Lolén Formation of the Ventana Group,Balarino, 2009, p.24 and the Sauce Grande, Piedra Azul, Bonete and Tunas Formations of the Pillahuincó Group, dating to the Permian.Balarino, 2009, p.22 During the late Paleozoic, the Colorado Basin was located in the south polar region, causing a sequence of glacial deposits in the basin.
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At the BFZ's eastern end, near the Steens Mountain fault, the zone of surface faulting turns slightly to the south-southeast (possibly due to rotation of Nevada), then follows the Northern Nevada Rift to form the Oregon-Nevada lineament, with a total length of over . Lavas associated with the Nevada Rift have been dated to 16.3 Ma (millions of years ago), close to the inception of basin-and- range faulting, but there is a suspicion that the rifting developed on an older strike-slip fault, possibly connected with the East Pacific Rise.. At its west end, just past the Newberry Volcano, the BFZ terminates at the north- striking Sisters Fault, part of the High Cascades geological province. But further south the Pliocene (<5 Ma) High Cascades volcanic trend is offset right-laterally about by the Eugene-Denio fault zone, and another by the McLoughlin zone.. At a possibly more fundamental level, the Brothers, Eugene- Denio, and McLoughlin zones, and possibly the Vale zone, all terminate near the Klamath - Blue Mountains Lineament (KBML; shortened and slightly misplaced on the map at right). The KBML is a prominent, long southwest-to-northeast- striking gravitational anomaly that crosses all of Oregon.
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According to some geologists, there is evidence that a mantle plume has existed in the region for about 140 million years, first remaining in roughly the same position while the African plate rotated above it, and then remaining stationary under the Oku area since around 66 million years ago. In this theory, the abnormal heat rising in a mantle plume would lead to melting of the upper mantle, which raises, thins and weakens the crust and facilitates rifting. This may have been repeated several times in the Benue Trough between 140 Ma and 49 Ma. One plume-related hypothesis for the later development of the Cameroon Line around 30 Ma is that it coincides with development of a shallow mantle convection system centered on the mantle plume, and is related to thinning and extension of the crust along the Cameroon line as pressures relaxed in the now stationary plate. The mantle plume hypothesis is disputed by scientists who point out that features of the region are quite different from what is predicted by that hypothesis, and that a source in a lithospheric fracture is more likely to be the explanation.
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The thick halite was later split into two main sections as the seafloor spread, with some continued salt deposition as the rifting continued. The age of the salts are supported by the stratigraphy in the northern Gulf of Mexico where the Eagle Mills red beds, as discussed above, contain dikes as young as 180 Ma, and the Smackover formation above the salts contain index ammonite fossils placing the salts at an age no younger than 156 Ma.The Gulf of Mexico Basin Salvador, Amos, J Geol. Soc. Am., Boulder, CO, United States( 1991) Deformation of this nearly 4-kilometer halite formation would eventually be caused by differential pressure due to uneven and heavy sediment loading on top, by siliciclastic, eolian, playa and other sediments characteristic of arid terrestrial environments closer to shore, implying that at certain times during deposition, sediments accumulated almost up to sea level. Simplified Stratigraphic Sequence of Northern Gulf of Mexico from the Late-Triassic through Early-Cretaceous The salt structures, which include anticlines, pillows, plugs and walls, in addition to extensive sheets, were created long after deposition by the rapid overlying sedimentation.
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In 1980, Philippe Masson of the University of Paris-Sud offered an integrated interpretation of the structural geochronology of Valles Marineris, Noctis Labyrinthus, and Claritas Fossae in light of imagery from Mariner 9 and the Viking Orbiter. In 2003, Daniel Mège (Pierre and Marie Curie University), Anthony C. Cook (University of Nottingham and the Smithsonian Institution), Erwan Garel (University of Maine in France), Yves Lagabrielle (University of Western Brittany), and Marie-Hélène Cormier (Columbia University) proposed a model for rifting on Mars initiated by the deflation of magma chambers, forming pit crater chains tracking directionally with simple graben. The researchers offered the first theoretical explanation as to how the chasmata of Noctis Labyrinthus formed. In 2012, a collaboration of French researchers Patrick Thollot, Nicolas Mangold, Véronique Ansan, and Stéphan Le Mouélic (University of Nantes), along with a cadre of American researchers including John F. Mustard (Brown University), Ralph E. Milliken (Notre Dame University), and Scott Murchie (Applied Physics Laboratory) reported on an unnamed basin in southeastern Noctis Labyrinthus showing an extremely wide assemblage of minerals known to form across a wide range of pH and water availability conditions.
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