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70-691: At the commencement of the deposition of the Dwyka Group, it is thought that the development of the Karoo supergroup foreland system had begun approximately 30 million years prior. This foreland system was caused by crustal uplift that had previously begun to take course due to the subduction of the Palaeo-pacific plate beneath the Gondwanan plate . This resulted in the rise of the Gondwanide mountain range in what

140-719: A cephalopod and some echinoids are also found in the north. During the Ecca period the Falklands Plateau collided and then fused with Southern Africa, forming a vast range of mountains to the south of the Cape Fold Belt. This new mountain range was comparable in size to the Himalayas . The northern slopes of these mountains generally dipped steeply into the Karoo Sea which was at its deepest at this point. The earthquakes that accompanied

210-429: A mountain belt . Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend, by a process known as lithospheric flexure . The width and depth of the foreland basin is determined by the flexural rigidity of the underlying lithosphere, and the characteristics of the mountain belt. The foreland basin receives sediment that

280-660: A retroarc foreland basin called the "main Karoo " Basin. This basin was formed by the subduction and orogenesis along the southern border of what eventually became Southern Africa, in southern Gondwana. Its sediments attain a maximum cumulative thickness of 12 km, with the overlying basaltic lavas (the Drakensberg Group) at least 1.4 km thick. Fossils include plants (both macro-fossils and pollen ), rare insects and fish , common and diverse tetrapods (mostly therapsid reptiles, temnospondyl amphibians, and in

350-409: A monotonous sequence of shales and mudstones , with some interbedded lenticular sandstones . The Beaufort Group is rich in reptilian, and to a lesser extent, amphibian remains. There is a plethora of both herbivorous and carnivorous reptile fossils. The Beaufort rocks are internationally famous for its rich record of therapsid synapsids (mammal-like reptiles), which mark an intermediary stage in

420-725: A phase of massive erosion, removing a layer several kilometers thick from the African Surface . Nearly all of the Drakensberg lavas were eroded away, leaving a remnant in Lesotho, several small patches on the Springbok Flats in the north of the country, and in the Lebombo mountains along the Mozambique border. Once the layer of hard lava was eroded away, the softer Karoo sediments over the rest of

490-607: A regime's tectonic origin and development as well as the lithospheric mechanics. Migrating fluids originate from the sediments of the foreland basin and migrate in response to deformation. As a result, brine can migrate over great distances. Evidence of long-range migration includes: 1) correlation of petroleum to distant source rocks , 2) ore bodies deposited from metal-bearing brines, 3) anomalous thermal histories for shallow sediments, 4) regional potassium metasomatism and 5) epigenetic dolomite cements in ore bodies and deep aquifers. Fluids carrying heat, minerals, and petroleum, have

560-458: 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. While the Drakensberg lavas form nearly horizontal layers, the Lebombo lavas dip to the east, so it is difficult to gauge how far the lava spread laterally. The uplifting of Southern Africa heralded

630-472: A single continuous 1 to 1.6 km thick lava layer. However, not all of the magma reached the surface, but extruded under high pressure between the horizontal strata of the Ecca and Beaufort rocks. When this magma solidified it formed multiple dolerite sills at various depths throughout the southern and south-western Karoo sediments. These sills vary in thickness from a few centimeters to hundreds of meters. This outpouring of lava coincided with uplifting of

700-510: A thorough definition of the foreland basin system. Foreland basin systems comprise three characteristic properties: The wedge-top sits on top of the moving thrust sheets and contains all the sediments charging from the active tectonic thrust wedge. This is where piggyback basins form. The foredeep is the thickest sedimentary zone and thickens toward the orogen. Sediments are deposited via distal fluvial, lacustrine, deltaic, and marine depositional systems. The forebulge and backbulge are

770-454: A vast impact on the tectonic regime within the foreland basin. Before deformation, sediment layers are porous and full of fluids, such as water and hydrated minerals. Once these sediments are buried and compacted, the pores become smaller and some of the fluids, about ⁠ 1 / 3 ⁠ , leave the pores. This fluid has to go somewhere. Within the foreland basin, these fluids potentially can heat and mineralize materials, as well as mix with

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840-410: Is a factor of temperature and time and occurs at shallower depths due to past heat redistribution of migrating brines. Vitrinite reflectance, which typically demonstrates an exponential evolution of organic matter as a function of time, is the best organic indicator for thermal maturation. Studies have shown that present day thermal measurements of heat flow and geothermal gradients closely correspond to

910-426: Is a function of topographic relief. For the loading model, the lithosphere is initially stiff, with the basin broad and shallow. Relaxation of the lithosphere allows subsidence near the thrust, narrowing of basin, forebulge toward thrust. During times of thrusting, the lithosphere is stiff and the forebulge broadens. The timing of the thrust deformation is opposite that of the relaxing of the lithosphere. The bending of

980-500: Is eroded off the adjacent mountain belt, filling with thick sedimentary successions that thin away from the mountain belt. Foreland basins represent an endmember basin type, the other being rift basins . Space for sediments (accommodation space) is provided by loading and downflexure to form foreland basins, in contrast to rift basins, where accommodation space is generated by lithospheric extension. Foreland basins can be divided into two categories: DeCelles & Giles (1996) provide

1050-577: Is found closer to the orogen and oil is found further away. Karoo Supergroup The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert . The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic , a period of about 120 million years. In southern Africa, rocks of

1120-558: Is known as the Gondwanide orogeny . The continuation of the orogenic pulses from the growing Gondwanides mountain chain and associated subduction created accommodation space for sedimentation in the Karoo Basin which ran along an east to west trending foreland trough. The formation of the Karoo Basin resulted in the preservation of the Dwyka Group rocks and all succeeding rocks that make up

1190-512: Is known by two distinctive lithological facies . These two facies are represented in its northern and southern deposits respectively and are recognized as the two geological formations below: The diamictites are highly compacted and overlie stratified diamictites and mudrocks. The southern facies is interpreted as suspension or melt-out deposits that were deposited in low energy subglacial or subaqueous rain-out from either semi-grounded or floating ice sheets . All sedimentation occurred below

1260-450: Is recognized and differentiated below due to its unique lithological facies from its main Karoo Basin counterparts: The Dwyka Group is mainly known for petrified wood which increase in species diversity in the younger sequences. The cold, glacial environment that the sedimentary rocks of the Dwyka Group were deposited in was not conducive for high plant diversity. Fossil wood species identified include lycopods , especially from

1330-576: The Drakensberg (although technically the "Drakensberg" refers to the entire 1000 km long eastern portion of the Great Escarpment, only about a third of which is capped by the Drakensberg lavas). The magma welled up through long crack-like fissures, with occasional spatter cones, but typical volcanoes were rare. Each surface lava flow was between 10 and 20 meters thick. These flows piled up in rapid succession over 2 million years, to form

1400-576: The Cape Supergroup , accumulated on the floor of this rift valley. Closure of the rift valley, starting 330 million years ago, resulted from the development of a subduction zone along the southern margin of Gondwana, and the consequent drift of the Falkland Plateau back towards Africa, during the Carboniferous and Early Permian periods. After closure of the rift valley, and compression of

1470-714: The Cape Supergroup , which includes the Cape Fold Belt , and the Natal Supergroup. It also unconformably overlies the Namaqua-Natal Metamorphic Province in some localities in the west-northwest of South Africa. Its north and northeastern Karoo Basin deposits and all deposits found north of the Karoo Basin unconformably overlie the Transvaal Supergroup , Ventersdorp Group, or Archean and Proterozoic basement rocks. In all South African localities,

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1540-453: The Karoo inland sea , into which icebergs which had calved off the glaciers and ice sheet to the north deposited vast quantities of mud and rocks of various sizes and origins. Such deposits are known as tillite . Further north, the ice sheet was grounded also leaving diamictite deposits whenever it partially melted, but, in addition, it scoured the bedrock, leaving behind striations (scratch marks) which can be seen near Barkly West in

1610-652: The South Pole , with the result that an ice sheet several kilometers thick covered much of Africa, and other parts of Gondwana. The glacial deposits from this ice sheet were the first of the sediments to be deposited to the north of the Cape Fold Mountains (and partially over these incipient mountains). The basin into which these sediments settled was deepest immediately north of the Cape Fold Mountain ranges. The ice sheet therefore floated on an inland lake, termed

1680-621: The Triassic Period (220 to 195 million years ago) and had fossilised foetal skeletons of Massospondylus , a prosauropod dinosaur. More examples of these eggs have since been found in the Golden Gate Highlands National Park , situated on the Clarens Formation rocks. Other fossils found in the park include those of advanced cynodontia (canine toothed animals), small thecodontia (animals with teeth set firmly in

1750-465: The Cape Supergroup into a series of parallel folds, running mainly east–west, the continued subduction of the paleo-Pacific Plate beneath the Falkland Plateau and the resulting collision of the latter with Southern Africa, raised a mountain range of immense proportions to the south of the former rift valley. The folded Cape Supergroup formed the northern foothills of this mountain range. The weight of

1820-471: The Dwyka Group are restricted to the edges of the Karoo Basin and achieve their greatest thickness in its southern deposits at approximately 800 m, progressively thinning out towards the north. In the south outcrops and exposures are known from Prince Albert , Matjiesfontein , Laingsburg , Sutherland , and as far south as Worcester . Western to northern exposures are known from Calvinia , Carnarvon , Kimberley , and then from Vryheid and Durban in

1890-572: The Dwyka Group underlies rocks of the Ecca Group . The geographical range of the Dwyka Group is large with its deposits also being found in other localities in southern Africa . Dwyka-aged deposits that are considered to correlate in age to those found in South Africa have been located in the southern Karasburg and Kalahari Basins of southern Namibia – in and around the Fish River Canyon – in

1960-594: The Falkland-Cape Supergroup mountains caused the continental crust of Southern Africa to sag, forming a retroarc foreland system, which became flooded to form the Karoo Sea. Sedimentation, beginning with glacial deposits from the north, but later from the Falkland Mountains to the south, into this depression formed the Karoo Supergroup . About 330 million years ago Gondwana had drifted over

2030-684: The Huab Basin of northern-western Namibia , the Waterberg and Owambo Basins of northern Namibia, the Dukwi Formation of the Kalahari Basin of Botswana , and the Save Basin of southeastern Zimbabwe . The Dwyka Group deposits have been categorized by those found as part of the Karoo Basin and smaller formations found in different basins north of the Karoo Basin. In the Karoo Basin , the Dwyka Group

2100-545: The Karasburg, Kalahari , and Huab Basins in Namibia . Glossopteris leaf impressions, the petrified remains of Dadoxylon , coprolites , fossil pollen , and trace fossils of bony fishes , crustaceans , and other arthropods have been found from the Dwyka Group and correlated geological formations from other basins. Foreland basin A foreland basin is a structural basin that develops adjacent and parallel to

2170-630: The Karoo Supergroup cover almost two thirds of the present land surface, making part of the 75% of sediments or sedimentary rocks covering the earth including all of Lesotho , almost the whole of Free State , and large parts of the Eastern Cape , Northern Cape , Mpumalanga and KwaZulu-Natal Provinces of South Africa . Karoo supergroup outcrops are also found in Namibia , Eswatini , Zambia , Zimbabwe and Malawi , as well as on other continents that were part of Gondwana . The basins in which it

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2240-435: The Karoo, and with it the appearance of a wide range of new species, including the dinosaurs , and true mammals during the late Triassic – early Jurassic. As Gondwana drifted north, conditions in the portion that was to become Southern Africa became increasingly hot and arid. Sandstones were the predominant rocks that formed. However, in some areas there was sufficient water to form swamps with consequent coal formation, but

2310-657: The Northern Cape, and in the grounds of the University of KwaZulu-Natal . This layer of tillite, traces of which can be found over a wide area of Southern Africa, India , and South America provided crucial early evidence in support of the Theory of Continental Drift . In South Africa the layer is known as the Dwyka Group . It is the earliest and lowermost of the Karoo Supergroup of sedimentary deposits. As Gondwana drifted away from

2380-656: The South Pole, the glaciers melted, leaving a vast inland sea, extending across South Africa, and neighboring regions of Gondwana. It might have had an opening to the ocean (similar to the Black Sea ) but tidal effects were small. Rivers draining mountains to the north of the Karoo Sea formed large swampy deltas in which plants belonging to the Glossopteris flora flourished. This dense vegetation accumulated as peat, which eventually turned into coal. The coal deposits are confined to

2450-499: 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,

2520-402: The active deformation zone with which it is connected. Today GPS measurements provide the rate at which one plate is moving relative to another. It is also important to consider that present day kinematics are unlikely to be the same as when deformation began. Thus, it is crucial to consider non-GPS models to determine the long-term evolution of continental collisions and in how it helped develop

2590-399: The adjacent foreland basins. Comparing both modern GPS (Sella et al. 2002) and non-GPS models allows deformation rates to be calculated. Comparing these numbers to the geologic regime helps constrain the number of probable models as well as which model is more geologically accurate within a specific region. Seismicity determines where active zones of seismic activity occur as well as measure

2660-436: The basin becomes completely filled. At this point, the basin enters the overfilled stage and deposition of terrestrial clastic sediments occurs. These are known as molasse . Sediment fill within the foredeep acts as an additional load on the continental lithosphere. Although the degree to which the lithosphere relaxes over time is still controversial, most workers accept an elastic or visco-elastic rheology to describe

2730-509: The basin eroded even faster. However, the dolerite sills resisted erosion, protecting the softer Beaufort and Ecca shales beneath them. This created numerous and widespread flat topped hills, known as Karoo Koppies ("koppie" being the Afrikaans term for hill), which are iconic of the Karoo, and, by extension, the South African landscape. The dykes , or vertical fissures which brought the lava to

2800-467: The course of several eruptions was more than 1600 m thick, especially in the east (in present-day Lesotho). This massive lava outpouring brought the Karoo sedimentation to an abrupt end. The name Drakensberg Group is derived from the fact that this layer forms the uppermost 1400 m of the Great Escarpment on the international border between Lesotho and KwaZulu-Natal, often referred to as

2870-499: The course of the laying down of the 6 km thick Beaufort deposits, the massive end-Permian mass extinction , 251 million years ago, extinguished about 96% of all species alive at that time. The global event can clearly be seen in the Beaufort rocks. A few members of the genus Lystrosaurus were the only mammal-like reptiles that survived this event. The Beaufort sediments that were laid down after this event tend to be coarser than

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2940-468: The east. Dwyka Group deposits are also found outside of and north of the Karoo Basin. These deposits found north of the Karoo Basin are found as the lowermost geological formation of the Springbok Flats, Tshipise, northern Lebombo, Tuli, and Ellisras ( Lephalale ) Basins of north-northeastern South Africa . In its southern, western, and eastern deposits, the Dwyka Group conformably overlies rocks of

3010-427: The evolution of the mammals from reptiles. The most abundant herbivores were the anomodonts , whose most primitive forms are also known from the Beaufort rocks. The dinocephalians (terrible head) are so named because of their extraordinary thick boned skulls, which were probably used for head butting during territorial fights. With their 3-meter body length, they were the first large animals to live on land. During

3080-501: The formation of the Cape Mountains therefore initiated frequent underwater mud- and rock-slides, forming fan-shaped accumulations of turbidites , which can be seen in the south west corner of the Karoo today (see photograph lower down on the right) the Ecca group also has its members that are named based on the lithologies of the locality they are in . Turbidites have for some time been recognized as petroleum producing rocks, because

3150-482: The greater Karoo Supergroup . Southern Africa at this time was part of the supercontinent , Gondwana , and was positioned over the antarctic circle at this time. The result was the development of the Permo-Carboniferous glacial environment where massive ice sheets entombed the early Karoo Basin in the surrounding highlands and permanent, floating glaciers in the lowlands. The geological formations of

3220-497: The jaw), bird-like and crocodile-like dinosaurs. About 182 million years ago the southern African portion of Gondwana passed over the Bouvet hotspot causing the crust under the Karoo Supergroup to rupture, releasing huge volumes of basaltic lava over the Clarens desert, covering nearly the whole of Southern Africa and other portions of Gondwana.The pile of lava that accumulated over

3290-497: The lithosphere under the orogenic load controls the drainage pattern of the foreland basin. The flexural tilting of the basin and the sediment supply from the orogen. Strength envelopes indicate that the rheological structure of the lithosphere underneath the foreland and the orogen are very different. The foreland basin typically shows a thermal and rheological structure similar to a rifted continental margin with three brittle layers above three ductile layers. The temperature underneath

3360-458: The lithosphere. Thus, the thrust belt is mobile and the foreland basin system becomes deformed over time. Syntectonic unconformities demonstrate simultaneous subsidence and tectonic activity. Foreland basins are filled with sediments which erode from the adjacent mountain belt. In the early stages, the foreland basin is said to be underfilled . During this stage, deep water and commonly marine sediments, known as flysch , are deposited. Eventually,

3430-425: The lithospheric deformation of the foreland basin. Allen & Allen (2005) describe a moving load system, one in which the deflection moves as a wave through the foreland plate before the load system. The deflection shape is commonly described as an asymmetrical low close to the load along the foreland and a broader uplifted deflection along the forebulge. The transport rate or flux of erosion, as well as sedimentation,

3500-457: The local hydrostatic head. Orogen topography is the major driving force of fluid migration. The heat from the lower crust moves via conduction and groundwater advection . Local hydrothermal areas occur when deep fluid flow moves very quickly. This can also explain very high temperatures at shallow depths. Other minor constraints include tectonic compression, thrusting, and sediment compaction. These are considered minor because they are limited by

3570-456: The north of the Karoo Sea had, by this time, been leveled by erosion and begun to be buried under newer sediments.) Several Mississippi-like rivers flowed over the silted up Karoo Basin from the south, creating rich new habitats for a variety of flora and fauna. The terrestrial (as opposed to lacunar or marine) deposits created by these rivers gave rise to the Beaufort Group . It is composed of

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3640-467: The northern shores of the early Permian Karoo Sea, and is mined today in the Highveld and KwaZulu-Natal. These sedimentary deposits are termed the Ecca Group of the Karoo Supergroup. They consist largely of shales and sandstones , and extend over the entire former Karoo Sea, but the southerly deposits do not contain coal, even though rivers from the Cape Fold Mountains formed small deltas. Although

3710-517: The ones that preceded them, probably because of a massive die-off of vegetation, which had protected the surface against erosion. These early Triassic sandstone-dominated strata are known as the Katberg formation (within the Beaufort Group), which accumulated to a thickness of 1 km. With time the Beaufort deposits became more fine-grained once again, probably indicating a recovery of the vegetation in

3780-411: The orogen is much higher and thus greatly weakens the lithosphere. According to Zhou et al. (2003), "under compressional stress the lithosphere beneath the mountain range becomes ductile almost entirely, except a thin (about 6 km in the center) brittle layer near the surface and perhaps a thin brittle layer in the uppermost mantle." This lithospheric weakening underneath the orogenic belt may in part cause

3850-404: The passive margin stage with orogenic loading of previously stretched continental margin during the early stages of convergence. Second, the "early convergence stage defined by deep water conditions", and lastly a "later convergent stage during which a subaerial wedge is flanked with terrestrial or shallow marine foreland basins". The temperature underneath the orogen is much higher and weakens

3920-440: The petroleum industry and geologists, who have found them to have rich and readily accessible deposits of oil and gas. Thus the north-eastern Ecca basin is rich in coal, while its south-western corner is becoming renowned for its oils reserves. With the formation of the Falkland Plateau and Cape Fold Mountain ranges, rivers from the south began to dominate the sedimentation in the Karoo Sea, which began to silt up. (The highlands to

3990-612: The quality is poor. The landscape probably resembled the Kalahari desert of today, with rivers like the present-day Orange River or the Nile running through it, sustaining localized areas of Triassic flora and fauna. The Stormberg Group contains South Africa's earliest dinosaur fossils. It also contains the fossil remains of the shrew-sized Megazostrodon , the oldest mammal in Africa. A remarkable array of insect and plant fossils are found in some of

4060-498: The regional lithospheric flexure behavior. Foreland basins are considered to be hypothermal basins (cooler than normal), with low geothermal gradient and heat flow . Heat flow values average between 1 and 2 HFU (40–90 mWm . Rapid subsidence may be responsible for these low values. Over time sedimentary layers become buried and lose porosity. This can be due to sediment compaction or the physical or chemical changes, such as pressure or cementation . Thermal maturation of sediments

4130-401: The slow rates of tectonic deformation, lithology and depositional rates, on the order of 0–10 cm yr , but more likely closer to 1 or less than 1 cm yr . Overpressured zones might allow for faster migration, when 1 kilometer or more of shaley sediments accumulate per 1 million years. Bethke & Marshak (1990) state that "groundwater that recharges at high elevation migrates through

4200-642: The strata. The uppermost strata of the Stormberg group were probably laid down under true sand desert conditions, similar to the Namib Desert in Namibia. It was probably as large as the Sahara Desert today, extending from the Cape Fold Mountains many thousands of kilometers northwards over large parts of Gondwana. Only a small remnant of this massive formation can be found in and around Lesotho today. This formation

4270-441: The subsurface in response to its high potential energy toward areas where the water table is lower." Bethke & Marshak (1990) explain that petroleum migrates not only in response to the hydrodynamic forces that drive groundwater flow, but to the buoyancy and capillary effects of the petroleum moving through microscopic pores. Migration patterns flow away from the orogenic belt and into the cratonic interior. Frequently, natural gas

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4340-479: The surface stand out today as linear ridges extending across large stretches of the Karoo. The continued erosion of Southern Africa over the past 180 million years has meant that rocks younger than The Drakensberg Group are almost non-existent over most of the interior. Some of the eroded material from the interior was trapped between the Cape Fold Mountains to the south during the Cretaceous Period to form

4410-429: The thinnest and most distal zones and are not always present. When present, they are defined by regional unconformities as well as aeolian and shallow-marine deposits. Sedimentation is most rapid near the moving thrust sheet. Sediment transport within the foredeep is generally parallel to the strike of the thrust fault and basin axis. The motion of the adjacent plates of the foreland basin can be determined by studying

4480-497: The total fault displacements and the timing of the onset of deformation. Foreland basins form because as the mountain belt grows, it exerts a significant mass on the Earth's crust, which causes it to bend, or flex, downwards. This occurs so that the weight of the mountain belt can be compensated by isostasy at the upflex of the forebulge. The plate tectonic evolution of a peripheral foreland basin involves three general stages. First,

4550-472: The underwater avalanches that cause these deposits often carry organic matter from close to the coastline, especially near river estuaries and deltas, into the anoxic depths of adjoining troughs. Here it is buried in the turbidite and turns into hydrocarbons , particularly petroleum and gas. The turbidites in the Ecca formation of the Tanqua and Laingsburg Karoo regions have thus, recently, come under scrutiny by

4620-477: The upper strata dinosaurs ), and ichnofossils . Their biostratigraphy has been used as the international standard for global correlation of Permian to Jurassic nonmarine strata. About 510 million years ago a rift valley developed across Southern Gondwana just south of Southern Africa, but extending westward into South America , and eastward into Eastern Antarctica and possibly even into Australia . An 8 km thick layer of sediment, known as

4690-525: The vegetation in the south was not as dense as on the northern shores of the inland sea, several early reptiles such as Mesosaurus are found in these Ecca deposits. This is a fossil reptile found only in Southern Africa and Brazil providing important paleontological evidence of the existence of the Gondwana supercontinent. The northern shores contain mainly fossil plants, pollens and spores. Fossils of

4760-514: The water surface in a deep marine environment. More evidence to support this is that turbidites are often found in Elandsvlei Formation deposits. North of the Karoo Basin outcrops of another geological formation that correlates in age to the main Karoo Basin's Dwyka-aged deposits. This formation is the lowermost unit of the Springbok Flats, Tshipise, northern Lebombo, Tuli, and Ellisras ( Lephalale ) Basins. This geological formation

4830-600: Was deposited formed during the formation and breakup of Pangea . The type area of the Karoo Supergroup is the Great Karoo in South Africa , where the most extensive outcrops of the sequence are exposed. Its strata, which consist mostly of shales and sandstones , record an almost continuous sequence of marine glacial to terrestrial deposition from the Late Carboniferous to the Early Jurassic . These accumulated in

4900-562: Was formerly known as “Cave Sandstone” as wind-eroded shallow caves often developed in cliffs made up of these rocks. These caves were later used by the San people who frequently decorated the walls with their paintings . Today the Cave Sandstones are called the Clarens Formation . The oldest dinosaur embryos ever discovered were found in the Clarens Formation in 1978. The eggs were from

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