Karoo Supergroup
The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Sahara 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, Swaziland, 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, mostly 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. 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.
Karoo
The Karoo (/kəˈruː/ kə-ROO; from a Khoikhoi word, possibly garo "desert") is a semi-desert natural region of South Africa. There is no exact definition of what constitutes the Karoo, and therefore its extent is also not precisely defined. The Karoo is partly defined by its topography, geology, and climate — above all, its low rainfall, arid air, cloudless skies, and extremes of heat and cold. The Karoo also hosted a well-preserved ecosystem hundreds of million years ago which is now represented by many fossils.
The Karoo formed an almost impenetrable barrier to the interior from Cape Town, and the early adventurers, explorers, hunters and travelers on the way to the Highveld unanimously denounced it as a frightening place of great heat, great frosts, great floods and great droughts. Today it is still a place of great heat and frosts, and an annual rainfall of between 50–250 mm, though on some of the mountains it can be 250–500 mm higher than on the plains. However, underground water is found throughout the Karoo, which can be tapped by boreholes, making permanent settlements and sheep farming possible.
Karoo (disambiguation)
The Karoo is a semi-desert region of South Africa.
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Karoo (crater)
Karoo is an impact crater on the Asteroid 253 Mathilde Named for the Great Karoo Basin, a Coal Basin in South Africa. It is 33.4 kilometers in diameter and was the most prominent crater seen during NEAR Shoemaker's Flyby of the Asteroid.
Mysteries on Karoo's Formation
The critical crater diameter is the scale at which cratering “goes global” and results in a solitary distinct crater.
All smaller craters—however large Dcrit might be—are local events. Mathilde is thus a particularly interesting case, since it is the largest asteroid imaged at sufficient resolution to show that its topography is clearly exogenic, governed by impacts. Mathilde has several craters rivaling Karoo in size; according to gravity-regime scaling it suffered ∼5 impacts by objects, ranging from ∼0.8 to 1.2 km diameter, without being struck once by an object large enough to disrupt it. This seems odd, and Cheng and Barnouin-Jha (1999) find Mathilde’s survival unlikely, and appeal to oblique impacts. But it may be an effect of preservation in the case where Dcrit is so large that even hemisphere-spanning craters are, by definition, “local.” If, for example, Mathilde’s attenuation is somewhat higher than usual, say α = 1.4, then based on Fig. 2 none of its craters exceeds the critical crater diameter. This would explain the crowding of giant craters, since none of these would result in global degradation. Indeed, if Karoo, at 33 km diameter, represents Dcrit and resurfaced the asteroid, then the 5 or more other giant impacts must have happened subsequently, which is highly unusual given that they are in fact almost just as large. Thus α = 1.33 from Fig. 2a is likely a lower limit on Mathilde’s attenuation.
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