The Transvaal Basin is one of three basins of the Transvaal Supergroup on the Kaapvaal craton. The evolution of this 2.65–2.05 Ga Neoarchaean–

Palaeoproterozoic The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6 Ga), is the first of the three sub-divisions (eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's ...

basin is thought to have been derived largely from

magmatism Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of ...

palaeoclimate Paleoclimatology ( British spelling, palaeoclimatology) is the study of climates for which direct measurements were not taken. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important to ...

and

eustasy The eustatic sea level is the distance from the center of the earth to the sea surface. An increase of the eustatic sea level can be generated by decreasing glaciation, increasing spreading rates of the mid-ocean ridges or more mid-oceanic ridges. ...

, while plate tectonics played an intermittent role. The supergroup is made up of basal ‘ protobasinal’ rocks, upon which followed the Black Reef Formation,

Chuniespoort Group Chuniespoort (recently Chuenespoort) is a mountain pass situated in the Limpopo Province, on the R37, the road between Polokwane and Lebowakgomo, South Africa. The river flowing through this gorge of the Strydpoort Mountains is known as the Ch ...

and the uppermost Pretoria Group. The Transvaal Supergroup displays three

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...

-bounded sequences that surface in two geographically distinct areas – the Transvaal Basin, which circumscribes the

Bushveld Igneous Complex The Bushveld Igneous Complex (BIC) is the largest layered igneous intrusion within the Earth's crust. It has been tilted and eroded forming the outcrops around what appears to be the edge of a great geological basin: the Transvaal Basin. It is ...

, and the

Griqualand West Griqualand West is an area of central South Africa with an area of 40,000 km2 that now forms part of the Northern Cape Province. It was inhabited by the Griqua people – a semi-nomadic, Afrikaans-speaking nation of mixed-race origin, w ...

basin, lying between Kimberley and

Sishen Dingleton is a town in Northern Cape, South Africa. The nearby Sishen mine is an iron ore mining activity, connected to the port of Saldanha Bay Saldanha Bay ( af, Saldanhabaai) is a natural harbour on the south-western coast of South Africa. ...

at the western Kaapvaal craton rim, extending into southern

Botswana Botswana (, ), officially the Republic of Botswana ( tn, Lefatshe la Botswana, label=Setswana, ), is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory being the Kalahar ...

beneath the

Kalahari Sands The Kalahari Desert is a large semi-arid sandy savanna in Southern Africa extending for , covering much of Botswana, and parts of Namibia and South Africa. It is not to be confused with the Angolan, Namibian, and South African Namib coastal de ...

as the Kanye Basin. The two basins are separated by the broad Vryburg Arch. Between approximately 2.640 and 2.516 Ga, two successive stromatolitic

carbonate platform A carbonate platform is a sedimentary body which possesses topographic relief, and is composed of autochthonic calcareous deposits. Platform growth is mediated by sessile organisms whose skeletons build up the reef or by organisms (usually microb ...

s developed in the basin of the Kaapvaal craton. Oldest was the Schmidtsdrif Subgroup, deposited in the southwestern part of the basin, showing stromatolitic carbonates, siliciclastic sediments and small lava flows. This was followed by the Nauga formation

carbonates A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

deposited on peritidal flats in the southwest, which were inundated during a

marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...

of the Transvaal Supergroup continental sea, at some 2.550 Ga. This resulted in a carbonate platform in the Transvaal and Griqualand West Basins, lasting for 30–50 Ma. Shales were deposited during this period over the Nauga Formation carbonates. Following this a subsidence led to immersion of the stromatolitic platform and to sediments of iron-rich

banded iron formations Banded iron formations (also known as banded ironstone formations or BIFs) are distinctive units of sedimentary rock consisting of alternating layers of iron oxides and iron-poor chert. They can be up to several hundred meters in thickness a ...

being laid down over the entire basin.P. G. Eriksson, W. Altermann; ''An overview of the geology of the Transvaal Supergroup dolomites (South Africa),'' Environmental Geology November 1998, Volume 36, Issue 1-2, pp 179-18
abstract
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References

{{reflist Geology of South Africa Sedimentary basins of Africa