A depocenter or depocentre in geology is the part of a sedimentary basin where a particular rock unit has its maximum thickness. [1] Depending on the controls on subsidence and the sedimentary environment, the location of a basin's depocenter may vary with time, such as in active rift basins as extensional faults grow, link or become abandoned. [2]
Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsidence creates a regional depression that provides accommodation space for accumulation of sediments. Over millions or tens or hundreds of millions of years the deposition of sediment, primarily gravity-driven transportation of water-borne eroded material, acts to fill the depression. As the sediments are buried, they are subject to increasing pressure and begin the processes of compaction and lithification that transform them into sedimentary rock.
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems.
The Los Angeles Basin is a sedimentary basin located in Southern California, in a region known as the Peninsular Ranges. The basin is also connected to an anomalous group of east-west trending chains of mountains collectively known as the Transverse Ranges. The present basin is a coastal lowland area, whose floor is marked by elongate low ridges and groups of hills that is located on the edge of the Pacific Plate. The Los Angeles Basin, along with the Santa Barbara Channel, the Ventura Basin, the San Fernando Valley, and the San Gabriel Basin, lies within the greater Southern California region. The majority of the jurisdictional land area of the city of Los Angeles physically lies within this basin.
Flysch is a sequence of sedimentary rock layers that progress from deep-water and turbidity flow deposits to shallow-water shales and sandstones. It is deposited when a deep basin forms rapidly on the continental side of a mountain building episode. Examples are found near the North American Cordillera, the Alps, the Pyrenees and the Carpathians.
The Sydney Basin is an interim Australian bioregion and is both a structural entity and a depositional area, now preserved on the east coast of New South Wales, Australia and with some of its eastern side now subsided beneath the Tasman Sea. The basin is named for the city of Sydney, on which it is centred.
Sedimentary exhalative deposits are zinc-lead deposits originally interpreted to have been formed by discharge of metal-bearing basinal fluids onto the seafloor resulting in the precipitation of mainly stratiform ore, often with thin laminations of sulfide minerals. SEDEX deposits are hosted largely by clastic rocks deposited in intracontinental rifts or failed rift basins and passive continental margins. Since these ore deposits frequently form massive sulfide lenses, they are also named sediment-hosted massive sulfide (SHMS) deposits, as opposed to volcanic-hosted massive sulfide (VHMS) deposits. The sedimentary appearance of the thin laminations led to early interpretations that the deposits formed exclusively or mainly by exhalative processes onto the seafloor, hence the term SEDEX. However, recent study of numerous deposits indicates that shallow subsurface replacement is also an important process, in several deposits the predominant one, with only local if any exhalations onto the seafloor. For this reason, some authors prefer the term clastic-dominated zinc-lead deposits. As used today, therefore, the term SEDEX is not to be taken to mean that hydrothermal fluids actually vented into the overlying water column, although this may have occurred in some cases.
The Adelaide Superbasin is a major Neoproterozoic to middle Cambrian geological province in central and south-east South Australia, western New South Wales, and western Victoria.
The U.S. state of Georgia is commonly divided into four geologic regions that influence the location of the state's four traditional physiographic regions. The four geologic regions include the Appalachian foreland, Blue Ridge, Piedmont, and Coastal Plain. These four geologic regions commonly share names with and typically overlap the four physiographic regions of the state: the Appalachian Plateau and adjacent Valley and Ridge; the Blue Ridge; the Piedmont and the Coastal Plain.
The Queen Charlotte Basin is a structural basin mostly beneath the continental shelf offshore, between Haida Gwaii, Vancouver Island, and the British Columbia mainland, roughly coincident with the physiographic region named the Hecate Depression.
The Hope Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate, from the transform Alpine Fault to the Hikurangi Trough subduction zone.
The Dead Sea Transform (DST) fault system, also sometimes referred to as the Dead Sea Rift, is a series of faults that run for about 1,000 km from the Maras Triple Junction to the northern end of the Red Sea Rift. The fault system forms the transform boundary between the African Plate to the west and the Arabian Plate to the east. It is a zone of left lateral (sinistral) displacement, signifying the relative motions of the two plates. Both plates are moving in a general north-northeast direction, but the Arabian Plate is moving faster, resulting in the observed left lateral motions along the fault of approximately 107 km at its southern end. A component of extension is also present in the southern part of the transform, which has contributed to a series of depressions, or pull-apart basins, forming the Gulf of Aqaba, Dead Sea, Sea of Galilee, and Hula basins. A component of shortening affects the Lebanon restraining bend, leading to uplift on both sides of the Beqaa valley. There is local transtension in the northernmost part of the fault system, forming the Ghab pull-apart basin. The southern part of the fault system runs roughly along the political border of Lebanon and Israel on its western side, and southern Syria and Jordan on the eastern side.
The Munster Basin is a late Middle to Upper Devonian age extensional (rift) sedimentary basin in the south-west of Ireland. The basin fill comprises fluvial Old Red Sandstone (ORS) magnafacies with minor silicic volcanic and mafic sub-volcanic centres. The depocentre of the basin is located between the MacGillycuddy's Reeks and the Kenmare River on the Iveragh peninsula where the succession is at least ca. 6 km thick. The non-marine ORS is conformably succeeded by latest Devonian coastal plain and shallow marine clastic deposits, followed by shallow to deeper marine Carboniferous sandstones, mudstones and limestones of the South Munster Basin. During the Late Palaeozoic Variscan orogeny the deposits in the basin were subjected to compressional deformation that resulted in pressure solution cleavage formation, buckle folding and contractional faulting under very low-grade metamorphic conditions.
Growth faults are syndepositional or syn-sedimentary extensional faults that initiate and evolve at the margins of continental plates. They extend parallel to passive margins that have high sediment supply. Their fault plane dips mostly toward the basin and has long-term continuous displacement. Figure one shows a growth fault with a concave upward fault plane that has high updip angle and flattened at its base into zone of detachment or décollement. This angle is continuously changing from nearly vertical in the updip area to nearly horizontal in the downdip area.
The Yinggehai-Song Hong Basin is located on the northwest of the South China Sea, between Hainan Island and the coast of northern Vietnam. It is a large extensional pull-part basin in extensional continental marginal setting, developed along the Red River fault zone, which located at the suture of the Indochina Plate and Yangtze Plate.
The Gulf of Corinth basin, or Corinth rift, is an active extensional marine sedimentary basin thought to have started deforming during the late Miocene – Pleistocene epoch. The dimensions of the Gulf of Corinth are approximately 105 km long and 30 km wide with a basement depth of 3 km at its center. This half-graben basin is formed by a N100°E-oriented rift which separates the Peloponnese peninsula from the continental mainland of Greece. Currently the Corinth rift is opening at rate of 10–15 mm/yr, with respect to the Eurasia Plate. The basin is bounded by the Peloponnese highlands to the south and the westward-moving Anatolian Fault to the north. Major and minor fault planes make up the north and south margins, and its north-south extension is due to activity along an E-W to NW-SE oriented coastal southern margin. The basin's active and inactive faults create associated syn-rift sediment fill. These aspects provide a unique opportunity for scientists to study the tectonic and stratigraphic development of a rift, while further understanding how a basin is actually made.
The Columbus Basin is a foreland basin located off the south eastern coast of Trinidad within the East Venezuela Basin (EVB). Due to the intensive deformation occurring along the Caribbean and South American plates in this region, the basin has a unique structural and stratigraphic relationship. The Columbus Basin has been a prime area for hydrocarbon exploration and production as its structures, sediments and burial history provide ideal conditions for generation and storage of hydrocarbon reserves. The Columbus Basin serves as a depocenter for the Orinoco River delta, where it is infilled with 15 km of fluvio-deltaic sediment. The area has also been extensively deformed by series of north west to southeast normal faults and northeast to southwest trending anticline structures.
The Kutai sedimentary basin extends from the central highlands of Borneo, across the eastern coast of the island and into the Makassar Strait. With an area of 60,000 km2, and depths up to 15 km, the Kutai is the largest and deepest Tertiary age basin in Indonesia. Plate tectonic evolution in the Indonesian region of SE Asia has produced a diverse array of basins in the Cenozoic. 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. It is also likely that regional climate, namely the onset of the equatorial ever wet monsoon in early Miocene, has affected the geologic evolution of Borneo and the Kutai basin through the present day. Basin fill is ongoing in the lower Kutai basin, as the modern Mahakam River delta progrades east across the continental shelf of Borneo.
The Omingonde Formation is an Early to Middle Triassic geologic formation, part of the Karoo Supergroup, in the western Otjozondjupa Region and northeastern Erongo Region of north-central Namibia. The formation has a maximum thickness of about 600 metres (2,000 ft) and comprises sandstones, shales, siltstones and conglomerates, was deposited in a fluvial environment, alternating between a meandering and braided river setting.
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. The basin contains a significant amount of natural gas and is a current source of commercial extraction.
The Hornelen Basin is a sedimentary basin in Vestland, Norway, containing an estimated 25 km stratigraphic thickness of coarse clastic sedimentary rocks of Devonian age. It forms part of a group of basins of similar age along the west coast of Norway between Sognefjord and Nordfjord, related to movement on the Nordfjord-Sogn Detachment. It formed as a result of extensional tectonics as part of the post-orogenic collapse of crust that was thickened during the Caledonian Orogeny towards the end of the Silurian period. It is named for the mountain Hornelen on the northern margin of the basin.
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