The Transvaal Basin is one of three

basins Basin may refer to: Geography and geology * Depression (geology) ** Back-arc basin, a submarine feature associated with island arcs and subduction zones ** Debris basin, designed to prevent damage from debris flow ** Drainage basin (hydrology), ...

of the Transvaal Supergroup on the Kaapvaal craton. The evolution of this 2.65–2.05 Ga Neoarchaean– Palaeoproterozoic basin is thought to have been derived largely from magmatism, palaeoclimate and

eustasy The eustatic sea level (from Greek εὖ ''eû'', "good" and στάσις ''stásis'', "standing") 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, i ...

, while

plate tectonics Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

played an intermittent role. The supergroup is made up of basal ‘ protobasinal’ rocks, upon which followed the Black Reef Formation, Chuniespoort Group and the uppermost

Pretoria Group Pretoria ( ; ) is the Capital of South Africa, administrative capital of South Africa, serving as the seat of the Executive (government), executive branch of government, and as the host to all foreign embassies to the country. Pretoria strad ...

. 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 intrusion, layered igneous intrusion within the Earth's Crust (geology), crust. It has been tilted and Erosion, eroded forming the outcrops around what appears to be the edge of a great Ba ...

, 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 Kimberly or Kimberley may refer to: Places and historical events Australia Queensland * Kimberley, Queensland, a coastal locality in the Shire of Douglas South Australia * County of Kimberley, a cadastral unit in South Australia Ta ...

and Sishen at the western Kaapvaal craton rim, extending into southern

Botswana Botswana, officially the Republic of Botswana, is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory part of the Kalahari Desert. It is bordered by South Africa to the sou ...

beneath the Kalahari Sands 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 rock, sedimentary body which possesses topographic relief, and is composed of Autochthon (geology), autochthonic calcareous deposits. Platform growth is mediated by Sessility (zoology), sessile organisms whose ...

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 flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

s. This was followed by the Nauga formation carbonates deposited on peritidal flats in the southwest, which were inundated during a

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

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.

Shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

s 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 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