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Gai-As Formation
The Gai-As Formation is an Early to Middle Permian ( Kungurian to Wordian) geologic formation correlated with the Ecca Group and designated "Ecca" Group, because it does not belong to the Karoo, in the southwestern Kunene Region and northern Erongo Region of northwestern Namibia. The Gai-As Formation represents the second-oldest sedimentary unit of the Huab Basin, overlying the Huab Formation. The formation was deposited in a fluvial to lacustrine setting. The Gai-As Formation is correlated with a series of formations in the Pelotas and Paraná Basins in southeastern Brazil, deposited in a larger basinal area, 150 million years before the break-up of Pangea. The abundance of '' Glossopteris'' and ''Mesosaurus'' fossils in the underlying Huab Formation are characteristic of the Gondwanan correlation across present-day South America, Africa, Antarctica and Australia. The Gai-As Formation has provided fossil bivalves and an indeterminate stereospondylid. Description The G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geological Formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob Wer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesosaurus
''Mesosaurus'' (meaning "middle lizard") is an extinct genus of reptile from the Early Permian of southern Africa and South America. Along with it, the genera '' Brazilosaurus'' and ''Stereosternum'', it is a member of the family Mesosauridae and the order Mesosauria. ''Mesosaurus'' was long thought to have been one of the first marine reptiles, although new data suggests that at least those of Uruguay inhabited a hypersaline water body, rather than a typical marine environment. In any case, it had many adaptations to a fully aquatic lifestyle. It is usually considered to have been anapsid, although Friedrich von Huene considered it to be a synapsid, and this hypothesis has been revived recently. Discovery and naming The holotype of ''M. tenuidens'', MNHN 1865-77, is nicknamed the "Griqua ''Mesosaurus''" and it was found in a Griqua hut in South Africa, likely in Kimberley, Northern Cape around 1830 and was being used as a pot lid. The circumstances of its discovery and how i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glossopteris
''Glossopteris'' tymology: from Ancient Greek γλῶσσα (glôssa, " tongue ") + πτερίς (pterís, " fern ")is the largest and best-known genus of the extinct Permian order of seed ferns known as Glossopteridales (also known as Arberiales, Ottokariales, or Dictyopteridiales). The genus ''Glossopteris'' refers only to leaves, within a framework of form genera used in paleobotany. (For likely reproductive organs see Glossopteridaceae.) Species of ''Glossopteris'' were the dominant trees of the middle- to high-latitude lowland vegetation across the supercontinent Gondwana during the Permian Period. ''Glossopteris'' fossils were critical in recognizing former connections between the various fragments of Gondwana: South America, Africa, India, Australia, New Zealand, and Antarctica. History The Glossopteridales arose in the Southern Hemisphere around the beginning of the Permian Period (), but became extinct during the end-Permian (Changhsingian) mass extinction. The putat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pangea
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million years ago, and began to break apart about 200 million years ago, at the end of the Triassic and beginning of the Jurassic. In contrast to the present Earth and its distribution of continental mass, Pangaea was centred on the equator and surrounded by the superocean Panthalassa and the Paleo-Tethys and subsequent Tethys Oceans. Pangaea is the most recent supercontinent to have existed and the first to be reconstructed by geologists. Origin of the concept The name "Pangaea" is derived from Ancient Greek ''pan'' (, "all, entire, whole") and '' Gaia'' or Gaea (, " Mother Earth, land"). The concept that the continents once formed a contiguous land mass was hypothesised, with corroborating evidence, by Alfred Wegener, the originator of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraná Basin
The Paraná Basin ( pt, Bacia do Paraná, es, Cuenca del Paraná) is a large cratonic sedimentary basin situated in the central-eastern part of South America. About 75% of its areal distribution occurs in Brazil, from Mato Grosso to Rio Grande do Sul states. The remainder area is distributed in eastern Paraguay, northeastern Argentina and northern Uruguay. The shape of the depression is roughly Ellipse, elliptical and covers an area of about . The Paraná River, from which the Paraná Basin derived its name, flows along the central axis of the Paraná Basin and drains it. Description The Paraná Basin stretches from the Brazilian state of Mato Grosso in the north to northern Argentina and Uruguay in the south. The southern portion in Uruguay is locally known as Norte Basin.De Santa Ana et al., 2004, p.88Daners et al., 2006, p.148 Pioneer studies The first study on the Brazilian side of the Paraná Basin dates from 1841, when a Brazilian Empire, Brazilian Imperial Govern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pelotas Basin
The Pelotas Basin ( pt, Bacia de Pelotas, es, Cuenca de Pelotas) is a mostly offshore sedimentary basin of approximately in the South Atlantic, administratively part of the southern states Santa Catarina and Rio Grande do Sul of Brazil and the departments Cerro Largo, Rocha and Treinta y Tres of Uruguay. The Pelotas Basin is one of the basins that formed on the present-day South Atlantic margins of South America and Africa due to the break-up of Gondwana in the Early Cretaceous. The sedimentary succession started as the other Brazilian marginal basins with a series of basalts, younger than the Paraná and Etendeka traps exposed in the Paraná Basin to the west, followed by shallow to deeper marine carbonate and clastic sediments. Other than the northern neighbours Santos and Campos Basins, the Pelotas Basin lacks a thick layer of salt and the pre-salt layer pinches out just in the north of the Pelotas Basin stratigraphy. Within the Brazilian Atlantic margin, the Pelotas Basi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lacustrine
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger oceans, they do form part of the Earth's water cycle. Lakes are distinct from lagoons, which are generally coastal parts of the ocean. Lakes are typically larger and deeper than ponds, which also lie on land, though there are no official or scientific definitions. Lakes can be contrasted with rivers or streams, which usually flow in a channel on land. Most lakes are fed and drained by rivers and streams. Natural lakes are generally found in mountainous areas, rift zones, and areas with ongoing glaciation. Other lakes are found in endorheic basins or along the courses of mature rivers, where a river channel has widened into a basin. Some parts of the world have many lakes formed by the chaotic drainage patterns left over from the last ice ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluvial
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvioglacial is used. Fluvial processes Fluvial processes include the motion of sediment and erosion or deposition on the river bed. The movement of water across the stream bed exerts a shear stress directly onto the bed. If the cohesive strength of the substrate is lower than the shear exerted, or the bed is composed of loose sediment which can be mobilized by such stresses, then the bed will be lowered purely by clearwater flow. In addition, if the river carries significant quantities of sediment, this material can act as tools to enhance wear of the bed ( abrasion). At the same time the fragments themselves are ground down, becoming smaller and more rounded (attrition). Sediment in rivers is transported as either bedload (the coarser fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Namibia
Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and east. Although Kazungula, it does not border Zimbabwe, less than 200 metres (660 feet) of the Botswanan right bank of the Zambezi, Zambezi River separates the two countries. Namibia gained independence from South Africa on 21 March 1990, following the Namibian War of Independence. Its capital and largest city is Windhoek. Namibia is a member state of the United Nations (UN), the Southern African Development Community (SADC), the African Union (AU) and the Commonwealth of Nations. The driest country in sub-Saharan Africa, Namibia has been inhabited since pre-historic times by the San people, San, Damara people, Damara and Nama people. Around the 14th century, immigration, immigrating Bantu peoples arrived as part of the Bantu expansion. Since ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karoo
The Karoo ( ; from the Afrikaans borrowing of the South Khoekhoe !Orakobab or Khoemana word ''ǃ’Aukarob'' "Hardveld") is a semi-desert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its extent is also not precisely defined. The Karoo is partly defined by its topography, geology and climate, and above all, its low rainfall, arid air, cloudless skies, and extremes of heat and cold.Potgieter, D.J. & du Plessis, T.C. (1972) ''Standard Encyclopaedia of Southern Africa''. Vol. 6. pp. 306–307. Nasou, Cape Town.''Reader’s Digest Illustrated Guide to Southern Africa''. (5th Ed. 1993). pp. 78–89. Reader’s Digest Association of South Africa Pty. Ltd., Cape Town. The Karoo also hosted a well-preserved ecosystem hundreds of million years ago which is now represented by many fossils. The ǃ’Aukarob formed an almost impenetrable barrier to the interior from Cape Town, and the early adventurers, explorers, hunters, and travelers o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formation (geology)
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob Wer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
