Karoo Supergroup
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The Karoo Supergroup is the largest geological feature in Southern Africa, covering almost two thirds of the present land surface, including central Cape Province, almost all of Orange Free State, western Natal, much of south-east Transvaal , Zambia, Zimbabwe and Malawi.
Its strata, mostly shales and sandstones (Hamilton & Finlay 1928), record an almost continuous sequence of marine glacial to terrestrial deposition from the Late Carboniferous to the Early Jurassic, a period of about a hundred million years. These accumulated in a retroarc foreland basin called the Karoo Basin. Its sediments attain a maximum cumulative thickness of 12 km, with the overlying basaltic lavas (the Stormbery Group) at least 1.4 km thick. (Adelmann and Fiedler 1996)
Fossils include plants (both macro-fossils and pollen), rare invertebrates 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. (Hancox & Rubidge, 1997)
The Karoo Supergroup is divided into the following strata (from oldest to youngest):
- Dwyka Group (glacial marine)
- Ecca Group
- Beaufort Group (terrestrial)
- Stormberg Group (including basalts)
[edit] See also
[edit] References
- Adelmann, D. and Fiedler, K., (1996), Sedimentary development of the Upper Ecca and Lower Beaufort Groups (Karoo Supergroup) in the Laingsburg subbasin (SW Karoo Basin, Cape Province/South Africa), Schriftenreihe der Deutschen Geologischen Gesellschaft, 1: 88-89, Bonn
- Hamilton, G.N.G. and Finlay, J.G. (1928), Outline of Geology for South African Students, Central News Agency Ltd, Johannesburg
- Hancox, P.J. & Rubidge, B.S. (1997), The role of fossils in interpreting the development of the Karoo basin. Palaeontol. Afr. 33: 41-54.
