Geology of South Africa
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The geology of South Africa is highly varied including
iron and coal from world-class deposits. The geomorphology of South Africa consists of a high plateau rimmed to west, south and southeast by the Great Escarpment, and the rugged mountains of the Cape Fold Belt. Beyond this there is strip of narrow coastal plain.[1]
Cratons and orogens
The basement of much of the northeastern part of South Africa is made up by the Kaapvaal Craton. To the south and east, the craton is bordered by the Namaqua-Natal belt.[2]
In
Dronning Maud Land.[3] Evidence of this is the continuation of the Namaqua-Natal belt in East Antarctica indicating that South Africa and East Antarctica formed a single continent when this belt formed about 1000 million years ago.[2]
Tectonics and erosion since the Mesozoic
Since the Mesozoic the tectonics of South Africa have been shaped by an initial phase of
Eastern Greenland and the Brazilian Highlands.[6] The uplift of these margins is tentatively related to far-field compressional stresses that has warped the region as a giant anticline-like lithosphere fold.[7] These tectonics have had a profound effect in shaping the Great Escarpment and uplifting, creating and destroying plateaux including the African Surface, a key reference surface.[4] On average, 2.5 to 3.5 km rock was eroded in the Mid to Late Cretaceous. Further erosion in Cenozoic times amount to less than one kilometer.[5] Limited erosion means that many of the major relief features of South Africa have existed since the Late Cretaceous.[8] Warping of Southern Africa has led to significant changes in drainage basins with the Orange River likely losing a drainage area in the Kalahari Basin, the Limpopo River losing interior drainage areas to the Zambezi River and the west-draining Karoo River ceasing to exist altogether.[9] Overall, the boundaries of the drainage basins coincide with the axes of uplifted epeirogenic flexures.[10]
Partridge and Maud (1987) links tectonics to three cycles of landscape development: African, Post-African I and Post-African II:[4]
- African cycle: The break-up of erosion cycle that begun with the Mesozoic rifting and uplift of Gondwana ended in the Miocene, albeit judging from offshore sediments erosion was minimal already in the Oligocene,[11] an epoch that nevertheless was one of large-scale crustal deformation.[8] It was during the African cycle, 70–40 million years ago that the etchplains that characterize the African Surface formed.[11] By the Miocene the African Surface was at an elevation of 600 to 500 m.[4]
- Post-African cycle I: Erosion increased again after 150–300 m of tectonic uplift tilted surfaces to the west in the Miocene. This erosion continued until the Pliocene. Albeit erosion surfaces were eroded into existence during the cycle no well-developed planation surface was formed. The Kalahari Basin accumulated large amounts of its sedimentary fill during this cycle as did also major oceanic basins surrounding the continent. Other sediments ended up making the formations of Uloa, upper Alexandria, Bredasdorp, Elandsfontyn, Varwater.[4]
- Post-African cycle II: In the Late Pliocene the central-eastern parts of Southern Africa were uplifted up to 900 m. This uplift led to increased
Stratigraphy
geological cross section through South Africa, with the Cape Peninsula (with Table Mountain) on the far left, and north-eastern KwaZulu-Natal on the right. Diagrammatic and only roughly to scale to scale. The difference in both composition and structure of the Cape Fold Mountains and the Central Plateau surrounded by the Great Escarpment, in particular the Drakensberg
, can clearly be seen.Cape Supergroup
The
Cape Supergroup is divided into several distinct Groups. The western and southern extents of the Supergroup have been folded into a series of longitudinal mountain ranges, by the collision of the Falkland Plateau into what would later become South Africa. However, the entire suite in this region slopes downwards towards the north and east, so that the oldest rocks are exposed in the south and west, while the youngest members of the Supergroup are exposed in the north, where the entire Cape Supergroup dives beneath the Karoo rocks. Drilling in the Karoo has established that Cape Supergroup rocks are found below the surface up to approximately 150 km north of their northernmost exposure on the surface. The Cape Supergroup extends eastwards beyond the Fold into the northern Eastern Cape and KwaZulu-Natal, where no folding took place.[12]
Karoo Supergroup
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.[13]
Transvaal Supergroup
The
Witwatersrand Basin (2,700 Mya) and the Bushveld Igneous Complex
(2,050 Mya).
Mineral resources
Diamond and gold production are now well down from their peaks. As of 2012[update], South Africa was the world's fifth-largest producer of gold but South Africa still possesses the world's second-largest reserves of gold.[14] It is the world's largest producer of chromium, manganese, platinum, vanadium and vermiculite and the second largest producer of ilmenite, palladium, rutile and zirconium.[15] South Africa is one of the ten largest coal producing countries in the world.[16][17] South Africa is also a huge producer of iron ore; in 2012, it overtook India to become the world's third biggest iron ore supplier to China, which is the world's largest consumer of iron ore.[18]
Prince Edward Islands
The
volcanic origin. Marion Island is the larger of the two islands and is one of the peaks of a large underwater shield volcano that rises some 5,000 metres (16,404 ft) from the sea floor to the top of Mascarin Peak. It is the only active South African volcano, with eruptions having occurred between 1980 and 2004.[19]
See also
- Geological Society of South Africa – A South African learned society for geology
References
- ^ "The World Factbook - South Africa". Cia.gov. Retrieved 2015-04-30.
- ^ .
- .
- ^ a b c d e f Partridge, T.C.; Maud, R.R. (1987). "Geomorphic evolution of southern Africa since the Mesozoic". South African Journal of Geology. 90 (2): 179–208.
- ^ .
- .
- .
- ^ a b c Baby, Guillaume (2016). "Mass transfer between the South African Plateau and the adjacent Atlantic Margin (Namibia - South Africa) since the Gondwana break-up". Source to Sink: a long term perspective of sediment budgets and sources characterization. Rennes, France. pp. 33–34.
- ^ .
- ^ Moore, A.E. (1999). "A reapprisal of epeirogenic flexure axes in southern Africa". South African Journal of Geology. 102 (4): 363–376.
- ^ .
- ISBN 978-0-360-00290-6.
- ISBN 978-3-540-76373-4.
- ^ "U.S. Geological Survey, Mineral Commodity Summaries, January 2013" (PDF). United States Geological Survey. January 2013.
- ^ "USGS Minerals Information: Mineral Commodity Summaries". Minerals.usgs.gov. 2015-01-30. Retrieved 2015-04-30.
- Technische Universität Bergakademie Freiberg. Retrieved 14 January 2010.
- World Coal Institute. Retrieved 14 January 2010.
- ^ "SA replaces India as China's No 3 iron-ore supplier". Mining Weekly. 2013-01-21.
- ^ "Marion Island". Global Volcanism Program. Retrieved 2015-04-30.
Further reading
Wikimedia Commons has media related to Geology of South Africa.
- Hatch, Frederick; Corstorphine, George Steuart (1905). The geology of South Africa. Macmillan and Co., limited.
- du Toit, Alexander (1954). The Geology of South Africa 3rd Ed. Oliver and Boyd.
- Haughton, Sidney H. (1969). Geological History of Southern Africa.