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46-579: 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

92-425: A ductile shale formation which was squeezed into shale diapirs in the basin. The Akata Formation formed during lowstands in relative sea level and anoxic conditions. This formation is estimated to be up to 7,000 meters thick. The Agbada Formation dates back to Eocene in age. It is a marine facies defined by both freshwater and deep sea characteristics. This is the major oil and natural gas -bearing facies in

138-574: A salt glacier . Differential loading causes salt deposits covered by overburden ( sediment ) to rise upward toward the surface and pierce the overburden, forming diapirs (including salt domes ), pillars, sheets, or other geological structures. In addition to Earth-based observations, diapirism is thought to occur on Neptune's moon Triton , Jupiter's moon Europa , Saturn's moon Enceladus , and Uranus's moon Miranda . Diapirs commonly intrude buoyantly upward along fractures or zones of structural weakness through denser overlying rocks. This process

184-425: A tide -dominated system that were deposited on a concave shoreline, and throughout time the shoreline became convex and it is currently a wave -dominated system. The oceanic basement rock is the oldest rock in the basin and is basaltic in composition. Also closer to the coast Precambrian continental basement crops out onshore. There is a section of rock in this basin from the middle to late Cretaceous which

230-448: A few are stable through time ( stable in this context means that the geometrical configuration of the triple junction will not change through geologic time). The meeting of four or more plates is also theoretically possible, but junctions will only exist instantaneously. The first scientific paper detailing the triple-junction concept was published in 1969 by Dan McKenzie and W. Jason Morgan . The term had traditionally been used for

276-476: A great oil trap. Clay smears in the sediments seal the formations so oil does not escape out. Basinward dipping reflectors are a common feature of extensional type rift basins. As fault blocks extend they rotate to dip towards the center of the basin. At the top of these fault blocks sub basins can form. The shale diapirs are from the Akata Formation. This structure is formed due to the improper dehydration of

322-736: A significant risk when trying to drill through them. There is an analogy to a Galilean thermometer . Rock types such as evaporitic salt deposits, and gas charged muds are potential sources of diapirs. Diapirs also form in the Earth's mantle when a sufficient mass of hot, less dense magma assembles. Diapirism in the mantle is thought to be associated with the development of large igneous provinces and some mantle plumes . Explosive, hot volatile rich magma or volcanic eruptions are referred to generally as diatremes . Diatremes are not usually associated with diapirs, as they are small-volume magmas which ascend by volatile plumes, not by density contrast with

368-454: A single point, for the triple junction to exist stably. These lines necessarily are parallel to the plate boundaries as to remain on the plate boundaries the observer must either move along the plate boundary or remain stationary on it. The point at which these lines meet, J, gives the overall motion of the triple junction with respect to the Earth. Using these criteria it can easily be shown why

414-442: Is Africa 's largest wetland. The Delta's environment can be broken down into four ecological zones: coastal barrier islands , mangrove swamp forests , freshwater swamps , and lowland rainforests . Fishing and farming are the main sources of livelihoods for majority of her residents. The delta is well endowed with natural resources and the surrounding ecosystem contains one of the highest concentrations of biodiversity on

460-474: Is a type of intrusion in which a more mobile and ductilely deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh–Taylor instability structures in regions with low tectonic stress such as in the Gulf of Mexico to narrow dikes of material that move along tectonically induced fractures in surrounding rock. The term

506-412: Is an extensional zone, which lies on the continental shelf, that is caused by the thickened crust. There is a transition zone, and then there is a contraction zone, which lies in the deep sea part of the basin. Basin inversion is caused by uplift and/or compression in this basin. The compression is caused by the toe detachment of the shale diapirs. Basin inversion forms anticline structures, which serve as

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552-456: Is believed to have caused the formation of the Pacific plate about 190 million years ago. By assuming that plates are rigid and that the Earth is spherical, Leonhard Euler 's theorem of motion on a sphere can be used to reduce the stability assessment to determining boundaries and relative motions of the interacting plates. The rigid assumption holds very well in the case of oceanic crust , and

598-468: Is demonstrated below – as the perpendicular bisectors of the sides of a triangle always meet at a single point, the lines ab, bc and ca can always be made to meet regardless of relative velocities. RTF junctions are less common, an unstable junction of this type (an RTF(a)) is thought to have existed at roughly 12 Ma at the mouth of the Gulf of California where the East Pacific Rise currently meets

644-418: Is known as diapirism . The resulting structures are also referred to as piercement structures . In the process, segments of the existing strata can be disconnected and pushed upwards. While moving higher, they retain many of their original properties, e.g. pressure; their pressure can be significantly different from the pressure of the shallower strata they get pushed into. Such overpressured "floaters" pose

690-402: Is poorly understood due to its significant burial depth. It is believed to be composed of sediments from a tide-dominated coastline, and there are believed to be several layers of shales, although their distribution is unconstrained. The Akata Formation is Paleocene in age. It is composed of thick shales, turbidite sands, and small amounts of silt and clay. The clay content resulted in it being

736-405: Is retained with time as the plates involved move. This places restrictions on relative velocities and plate boundary orientation. An unstable triple junction will change with time, either to become another form of triple junction (RRF junctions easily evolve to FFR junctions), will change geometry or are simply not feasible (as in the case of FFF junctions). The inherent instability of an FFF junction

782-423: Is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of three types – a ridge (R), trench (T) or transform fault (F) – and triple junctions can be described according to the types of plate margin that meet at them (e.g. fault–fault–trench, ridge–ridge–ridge, or abbreviated F-F-T, R-R-R). Of the ten possible types of triple junctions only

828-592: The Mid-Atlantic Ridge , and an associated aulacogen , the Benue Trough , 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. The stability of RRR junctions

874-781: The Philippine and Pacific plates , with the Philippine plate also overriding the Pacific. Here the Japan Trench effectively branches to form the Ryukyu and Bonin arcs . The stability criteria for this type of junction are either ab and ac form a straight line or that the line bc is parallel to CA. Diapirism A diapir ( / ˈ d aɪ . ə p ɪər / ; from French diapir [djapiʁ] , from Ancient Greek διαπειραίνω ( diapeiraínō )  'to pierce through')

920-556: The San Andreas Fault zone. The Guadeloupe and Farallon microplates were previously being subducted under the North American plate and the northern end of this boundary met the San Andreas Fault . Material for this subduction was provided by a ridge equivalent to the modern East Pacific Rise slightly displaced to the west of the trench. As the ridge itself was subducted an RTF triple junction momentarily existed but subduction of

966-488: The Euler poles are distant from the triple junction concerned. The definitions they used for R, T and F are as follows: For a triple junction between the plates A, B and C to exist, the following condition must be satisfied: where A v B is the relative motion of B with respect to A. This condition can be represented in velocity space by constructing a velocity triangle ABC where the lengths AB, BC and CA are proportional to

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1012-637: The FFF triple junction is not stable: the only case in which three lines lying along the sides of a triangle can meet at a point is the trivial case in which the triangle has sides lengths zero, corresponding to zero relative motion between the plates. As faults are required to be active for the purpose of this assessment, an FFF junction can never be stable. McKenzie and Morgan determined that there were 16 types of triple junction theoretically possible, though several of these are speculative and have not necessarily been seen on Earth. These junctions were classified firstly by

1058-613: The Forcados estuary, affecting the sea species and surrounding swamp forest. In January 1980, the Funiwa No.5 Well in Funiwa Field spilled 421 thousand barrels of oil into the ocean, damaging 836 acres of mangrove forest. In 1983, 5 000 barrels were spilled causing high mortality in crabs, fish and shrimps. Until 1999, an average of 240 thousand barrels of crude oil was spilled in the zone every year. Triple junction A triple junction

1104-566: 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

1150-478: The RRF configuration could be stable under certain conditions. 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 a 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

1196-461: The basin. The hydrocarbons in this layer formed when this layer of rock became subaerial and was covered in a marsh -type environment rich in organic content. It is estimated to be 3,700 meters thick. The Benin Formation is Oligocene and younger in age. It is composed of continental flood plain sands and alluvial deposits. It is estimated to be up to 2,000 meters thick. The tectonic structures in

1242-458: The deep-sea part of the basin. The sediment fill in the Niger Delta basin is characterized by three major depobelts. These three cycles show that the basin experienced an overall regression throughout time as the sediments go from deep sea mud sized grains to fluvial denser sand sized grains. The lithologies of the area experience changes due to several factors. The sediment provenance from

1288-400: The formation and the over pressuring by the overlying and denser Agbada Formation. High-angle normal faulting is a feature of the extensional portion of the rifting in this basin. It is considered a growth fault and the feature lies closer towards the basins edge and transitions to the toe detachment faulting as you continue down the basin. The Niger Delta is the twelfth largest province in

1334-410: The geological details but simply by defining the properties of the ridges , trenches and transform faults involved, making some simplifying assumptions and applying simple velocity calculations. This assessment can generalise to most actual triple junction settings provided the assumptions and definitions broadly apply to the real Earth. A stable junction is one at which the geometry of the junction

1380-426: The intersection of three divergent boundaries or spreading ridges. These three divergent boundaries ideally meet at near 120° angles. In plate tectonics theory during the breakup of a continent, three divergent boundaries form, radiating out from a central point (the triple junction). One of these divergent plate boundaries fails (see aulacogen ) and the other two continue spreading to form an ocean. The opening of

1426-632: The late Cretaceous. This indicates that the shoreline regressed during this time. Concurrently, the basin had been undergoing extension resulting in high angle normal faults and fault block rotation. At the beginning of the Paleocene there was a significant shoreline transgression. During the Paleocene, the Akata Formation was deposited, followed by the Agbada Formation during the Eocene. This loading caused

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1472-403: The onshore highlands which feed into the delta control the mineralogy of the grains. Additionally, the impact of sea level on sediment deposition is well known; relative sea level will control the basinward extent of lithologies (see sequence stratigraphy ). Volcanic activity in the area may also result in thin deposits of ash ( bentonite ). The early Cretaceous sediments are thought to be from

1518-458: The planet. In addition to supporting abundant flora and fauna , arable terrain that can sustain a wide variety of crops, lumber or agricultural trees , and more species of freshwater fish than any ecosystem in West Africa . The advent of oil production has also negatively impacted the Niger Delta region due to unprecedented oil spillage which has been ongoing for the past 5 decades making

1564-464: The purely kinematic point of view where the plates are rigid and moving over the surface of the Earth. No knowledge of the Earth's interior or the geological details of the crust are then needed. Another useful simplification is that the kinematics of triple junctions on a flat Earth are essentially the same as those on the surface of a sphere. On a sphere, plate motions are described as relative rotations about Euler poles (see Plate reconstruction ), and

1610-446: The radius of the Earth at the equator and poles only varies by a factor of roughly one part in 300 so the Earth approximates very well to a sphere. McKenzie and Morgan first analysed the stability of triple junctions using these assumptions with the additional assumption that the Euler poles describing the motions of the plates were such that they approximated to straight line motion on a flat surface. This simplification applies when

1656-540: The region one of the most polluted in the world. The heavy contamination of the air, ground and water with toxic pollutants is often used as an example of ecocide . It is estimated that while the European Union experienced 10 incidences of oil spills in 40 years, Nigeria recorded 9,343 cases within 10 years. In July 1979, an incident on the coastal zone of the Forcado tank 6 terminal spilled 570 thousand barrels of oil into

1702-518: The relative motion at every point along a plate boundary can be calculated from this rotation. But the area around a triple junction is small enough (relative to the size of the sphere) and (usually) far enough from the pole of rotation, that the relative motion across a boundary can be assumed to be constant along that boundary. Thus, analysis of triple junctions can usually be done on a flat surface with motions defined by vectors. Triple junctions may be described and their stability assessed without use of

1748-522: The ridge caused the subducted lithosphere to weaken and 'tear' from the point of the triple junction. The loss of slab pull caused by the detachment of this lithosphere ended the RTF junction giving the present day ridge – fault system. An RTF(a) is stable if ab goes through the point in velocity space C, or if ac and bc are colinear. A TTT(a) junction can be found in central Japan where the Eurasian plate overrides

1794-436: The same velocity space diagrams in the following way. The lines ab, bc and ca join points in velocity space which will leave the geometry of AB, BC and CA unchanged. These lines are the same as those that join points in velocity space at which an observer could move at the given velocity and still remain on the plate boundary. When these are drawn onto the diagram containing the velocity triangle these lines must be able to meet at

1840-499: The south Atlantic Ocean started at the south of the South American and African continents, reaching a triple junction in the present Gulf of Guinea , from where it continued to the west. The NE-trending Benue Trough is the failed arm of this junction. In the years since, the term triple-junction has come to refer to any point where three tectonic plates meet. The properties of triple junctions are most easily understood from

1886-440: The surrounding mantle. Diapirs or piercement structures are structures resulting from the penetration of overlaying material. By pushing upward and piercing overlying rock layers, diapirs can form anticlines (arch-like shape folds ), salt domes (mushroom/ dome-shaped diapirs), and other structures capable of trapping hydrocarbons such as petroleum and natural gas . Igneous intrusions themselves are typically too hot to allow

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1932-499: The types of plate boundaries meeting – for example RRR, TTR, RRT, FFT etc. – and secondly by the relative motion directions of the plates involved. Some configurations such as RRR can only have one set of relative motions whereas TTT junctions may be classified into TTT(a) and TTT(b). These differences in motion direction affect the stability criteria. McKenzie and Morgan claimed that of these 16 types, 14 were stable with FFF and RRF configurations unstable, however, York later showed that

1978-531: The underlying shale Akata Formation to be squeezed into shale diapirs. Then in the Oligocene the Benin formation was deposited, which is still being deposited today. 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, caused by the thickened crust. Moving basinward is a transition zone, and a contraction zone, which lies in

2024-433: The velocities A v B , B v C and C v A respectively. Further conditions must also be met for the triple junction to exist stably – the plates must move in a way that leaves their individual geometries unchanged. Alternatively the triple junction must move in such a way that it remains on all three of the plate boundaries involved. McKenzie and Morgan demonstrated that these criteria can be represented on

2070-668: The world by known oil and gas resources. The Niger Delta Basin produces around 2 million barrels of oil per day. The entire system is predicted to contain 34.5 billion barrels of oil and 94 trillion feet of natural gas. This area is still very heavily explored by oil companies today. It is one of the largest oil producers in the world. Petroleum extraction in the Niger Delta has led to many environmental issues . The delta covers 20,000 km (7,700 sq mi) within wetlands , formed primarily by sediment deposition. Home to 20 million people and 40 different ethnic groups , this floodplain makes up 7.5% of Nigeria's total land mass, and

2116-433: Was introduced by Romanian geologist Ludovic Mrazek , who was the first to understand the principle of salt tectonics and plasticity . The term diapir may be applied to igneous intrusions , but it is more commonly applied to non-igneous, relatively cold materials, such as salt domes and mud diapirs. If a salt diapir reaches the surface, it can flow because salt becomes ductile with a small amount of moisture, forming

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