Оңтүстік Африкадағы Кару супертобының геологиялық құрылымы

Widespread Mesozoic stratigraphic unit in southern Africa

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 the Karoo Supergroup cover almost two thirds of the present land surface, 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 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 a retroarc foreland basin called the "main Karoo" Basin. Fossils include plants (both macro fossils and pollen), rare insects and fish, common and diverse tetrapods (mostly therapsid reptiles, temnospondyl amphibians, and in 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 possible even into Australia. An 8 km thick layer of sediment, known as the Cape Supergroup, accumulated on the floor of this rift valley.

About 330 million years ago Gondwana had drifted over the South Pole, with the result that an ice sheet several kilometers thick covered much of Africa, and other parts of Gondwana. 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 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. Turbidites have for some time been recognized as petroleum producing rocks, because 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 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. The eggs were from 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 the jaw), bird like and crocodile like dinosaurs.