The geology of Namibia encompasses rocks of Paleoproterozoic, Mesoproterozoic and Neoproterozoic and Paleozoic to Cenozoic age. About 46% of the countryʼs surface are bedrock exposure, while the remainder is covered by the young overburden sediments of the Kalahari and Namib deserts.
The country is famous for its mineral deposits of Tsumeb, as well as many geological sites of interest, from paleontological, geomorphological and volcanic character. Due to the exposure of the formations in a desert climate and the former German colony, the geology of Namibia is relatively well studied compared to the more tropical less exposed northern neighbors.
Stratigraphy and tectonics
Large areas of the Namibian geology exposed onshore are associated with the Late Proterozoic Pan-African orogenic cycle.[1] The geology of Namibia is dominated in the north by metasediments of the Neoproterozoic Damara Belt (or Namibian System), while in the south large areas are underlain by the unmetamorphosed, relatively undisturbed sediments of the Cambrian Nama Group. Locally, within the Damaran terrain, inliers of older basement occur, for instance in the extreme northwest at the Kunene River the oldest rocks of the country belong to the Paleoproterozoic (about 2,100 Ma) Epupa Metamorphic Complex. Only slightly younger are metamorphic rocks of the Huab Complex west of Outjo. Similar ages are also recorded from rocks of the Grootfontain Metamorphic Complex in the northeast of the country.[2]
The Rehoboth-Sinclair Complex in Namibiaʼs southwest is of late Paleoproterozoic or Mesoproterozoic age. The Epupa and Huab Complexes were attached to the Congo Craton, whilst the Grootfontain and the volcano-sedimentary formations of the Rehoboth-Sinclair Complexes were assembled with the Kalahari Craton. The Namaqua Metamorphic Complex consists of metasediments originally eroded from the Congo and Kalahari Cratons. Granitic and metabasic intrusions also occur. It is of Mesoproterozoic age and covers large areas in the south and southwest of the country. Of Neoproterozoic age are the rocks of the Damara Orogenic Belt, which are widespread in central and northern Namibia. These are high grade metamorphics, but granitic intrusions are also frequent. In the Neoproterozoic Damara Orogen and Gariep Belt, mineralisation is associated with successive phases of intracontinental rifting (copper, graphite), spreading and the formation of passive continental margins.[3] The overlying rocks of the Nama Group in central southern Namibia consist of marine sediments indicating a shallow shelf environment, deposited during the Ediacaran and earliest Cambrian. The clastic components of the Nama Group were mainly derived from the Damara Orogenic Belt, while the basal pelites and carbonates have eastern provenance areas.
No deposition is recorded from the Cambrian until the beginning of the Karoo episode, which in its initial phase is characterized by glacial sediments of the Dwyka Group. This type of rocks is well-distributed in the Kaokoveld of northwest Namibia. It is followed by continental sediments of the Omingonde Formation of the Ecca and Stormberg Groups in central Namibia. The Permo-Triassic Karoo Sequence is intruded by mostly Mesozoic dolerite sills and dyke swarms, which, together with extensive basaltic volcanism and alkaline sub-volcanic intrusions, are related to the breakup of Gondwana, and the formation of the South Atlantic Ocean during the Cretaceous. The currently last chapter of the geological history of the country is represented by the widespread Cenozoic to recent deposits of the Kalahari Sequence.
Sedimentary basins
Namibia hosts the following sedimentary basins:
| On/offshore | Name | Location | Notes |
|---|---|---|---|
| Onshore | Orupembe Basin | Kunene Region | [4] |
| Huab Basin | [4] | ||
| Etosha, Rundu or Owambo Basin | Kavango Region Otjozondjupa Region Omaheke Region | [4][5] | |
| Waterberg Basin | Otjozondjupa Region | [4][5] | |
| Kalahari or Nama Basin | Omaheke Region Hardap Region ǁKaras Region | [4][5] | |
| Karasberg or Warmbad Basin | ǁKaras Region | [4][5] | |
| Dordabis Basin | Khomas Region Omaheke Region | [6] | |
| Witvlei Basin | Omaheke Region | ||
| Klein Aub Basin | Erongo Region | ||
| Sinclair Basin | Hardap Region | ||
| Offshore | Namibe Basin | Northwest | [5] |
| Walvis Basin | |||
| Lüderitz Basin | West | ||
| Orange Basin | Southwest | ||
Paleontology
While fossiliferous stratigraphic units are relatively rare in Namibia, the unique Ediacaran to Early Cambrian biota of the Nama Group are a major paleontological highlight. The Late Carboniferous to Early Permian Ganigobis Formation has provided fossil fishes and the younger White Hill, Huab and Gai-As Formations of the Dwyka Group contain Mesosaurus fossils. The Mesozoic is represented by the Triassic Omingonde Formation comprising therapsid fossils and the Early Jurassic Etjo Sandstone with dinosaur trackways.[7] The Eocene Buntfeldschuch and Langental Formations contain numerous fossil fish and the Early Miocene Elisabeth Bay Formation shows a diverse fauna with snake and mammal fossils.[8][9]
Roter Kamm crater
The Pliocene Roter Kamm crater is a 2.5 kilometres (1.6 mi) diameter and 130 metres (430 ft) deep circular impact crater in ǁKaras Region in the Kalahari Desert, about 80 kilometres (50 mi) north of Oranjemund. The age is estimated to be 4.81 ± 0.5 Ma and the crater is exposed at the surface, but its original floor is covered by sand deposits at least 100 metres (330 ft) thick. The meteor that hit it was approximately the size of an SUV.[10]
Economic geology
Tsumeb is a world-famous site for minerals. In the district, 309 different minerals are recorded and the area hosts 72 type localities of minerals and one first reported locality of an unapproved mineral, zinclavendulan, a variety of lavendulan.[11] The minerals arsentsumebite (Pb2Cu(AsO4)(SO4)(OH)) and tsumebite (Pb2Cu(PO4)(SO4)(OH)) are named after Tsumeb.[12][13]
Targets for mineral exploration have been identified throughout the stratigraphic column. Metamorphic complexes host a variety of prospective environments such as copper-molybdenum porphyry, volcanic base metals and gold, volcanogenic copper, sedimentary lead and zinc, fluorite, shear zone gold, and beryllium-niobium-tantalum mineralization. Paleoproterozoic to Mesoproterozoic rocks locally contain extensive red bed copper, while calc-alkaline units of the same age have potential for porphyry and hydrothermal copper, as well as vein-type gold mineralization. Namibia is one of the major producers of diamonds, 95% of which are of gem quality. The bulk of the countryʼs known diamonds occur along the southern coastline, north of the Orange River mouth.[14]
The diamonds originated in the interior of southern Africa and were transported by the Orange River to the Atlantic coast, where they were deposited within beach sediments. Almost the entire coastline is covered by exploration and mining licenses. Offshore mining techniques have been pioneered in Namibia and the country has firmly been established as the world leader in marine diamond mining. Inland, in the vicinity of Gibeon, 60 barren pipes of kimberlite of post-Karoo age have been identified. The northeast of the country also hosts some kimberlites, which are currently being explored for their diamond potential. The main occurrences of gold are in the Karibib and Rehoboth regions, the Omaruru area and the Kunene region. Silver is present in several deposits mined principally for their copper, lead and zinc contents.
It is found in the ore bodies of Tsumeb, Kombat and Rosh Pinah mines. Graphitic deposits in the Damara Sequence, calcrete hosted deposits of the Tertiary and sedimentary deposits in sandstones of the Karoo Supergroup, are the three major types of uranium hosting lithologies in Namibia. The deposits at Rössing and Valencia are of granitic origin. In the mid-2000s, Rössing was the countryʼs only producer of uranium. Major base metal production in Namibia includes copper, lead and zinc. Large-scale mining of base metals, especially copper, plays an important role in the economy of the country. Copper occurs at several locations, but is dominated by the Damara deposits: Otavi Mountainland (including the defunct Tsumeb Mine) and the Matchless Amphibolite Belt of the Swakop Group. Minor amounts come from Rosh Pinah. A feasibility study of the Skorpion zinc project has confirmed that Skorpion could rank as one of the worldʼs largest integrated zinc mining and refining operations. Haib, at the border with South Africa, is a classic porphyry copper-gold-molybdenum deposit featuring oxide and sulphide copper with a predominance of chalcopyrite in the sulphide ores.
Salt is recovered on a large scale from coastal solar evaporation pans in the Swakopmund and Walvis Bay areas, and at Cape Cross. The Okorusu Fluorspar Mine produces high quality acid-grade fluorspar. The Okanjande graphite deposit near Otjiwarongo is composed of high quality flake graphite, but the mine has not yet gone into operation. Wollastonite is produced in the Usakos area. Namibia also produces a variety of semi-precious stones through both small and medium-scale mining. tourmaline, aquamarine, heliodor, morganite, rose quartz, smoky quartz, garnet, chrysocolla and dioptase are quarried in various parts of the country. Marble, granite and other dimension stone for export or local processing are produced between Swakopmund and Karibib.[15]
Petroleum geology
The Namibian Atlantic margin is conjugate with the Pelotas Basin of Rio Grande do Sul and northeastern Uruguay. Both basins are compared to their northern counterparts, for the Walvis Basin in Namibia the Kwanza Basin of Angola, and for the Pelotas Basin the Santos Basin of Brazil, underexplored. Apart from the discovery of the offshore Kudu Gas Field, exploration intersected oil-prone source rocks in boreholes, of merely five wells until 2004.[16] The Walvis Basin is bound by the Walvis Ridge, which formed a barrier in the opening of the Southern Atlantic in the Aptian leading to salt basins to the north and basins without evaporite deposits to the south. The ridge, in South America correlated with the Rio Grande Rise, both related with the Tristan da Cunha hotspot, also represents the boundary between volcanic and non-volcanic areas to the south and north respectively.[17] Cenomanian-Turonian oil-prone source rocks have been penetrated by wells in the Walvis Basin.[18]
Namibia imports all its power station requirements. A large low-grade coalfield was found near Aranos, at depths of 250 to 300 metres (820 to 980 ft). Large, low-grade anthracite coal deposits are located along the coastline between the Huab River and Toscanini. Industrial mineral production in Namibia includes salt, fluorspar, wollastonite and dimension stone.[15]
Geological sites
Namibiaʼs geological exposures contribute to a wide variety of geological sites. Some of them have already been protected, but some are unfortunately already spoiled. A formal inventory has provided 32 sites:
- Brandberg
- Brukkaros Mountain
- Burnt Mountain
- Dieprivier
- Dolerite Hills
- Etendeka Plateau
- Erongo
- Etosha Pan
- Fish River Canyon
- Gamsberg
- Gibeoan Meteorites
- Hoba Meteorite
- Kalahari Desert
- Karas Mountains
- Kolmanskop
- Kuiseb Canyon
- Lake Otjikoto and Lake Guinas
- Messum
- Mount Etjo
- Mukorob
- Namib Desert
- Naukluft
- Omatako Mountains
- Organ Pipes
- Dinosaur tracks at Otjihaenamparero
- Petrified forest, Khorixas
- Sesriem Canyon
- Sossusvlei
- Tsondabvlei
- Spitzkoppe
- Twyfelfontein
- Vingerklip
- Waterberg
A spoiled geological monument is the Mukorob or "Finger of God", a weather resistant remnant of a sandstone pinnacle that was left standing on its own as erosion slowly cut back the surrounding Weissrand Escarpment of the Karoo Supergroup in southern Namibia. The Mukorob consisted of a large head of sandstone supported by a narrow neck of soft, fragmented mudstone. The head was almost 12 metres (39 ft) high and weighed about 450 tonnes (440 long tons; 500 short tons). On 8 December 1988, the Mukarob collapsed, possibly due to a destructive earthquake that had occurred the previous day in Armenia, but which was recorded strongly on the seismograph in Windhoek.
The petrified forest near Khorixas in northwest Namibia is an impressive paleontological monument, which may serve as an already well protected geological site. Similarly, the Hoba Meteorite in northern Namibia, which is the largest known iron meteorite on Earth, is well protected as a national monument and attracts many visitors at the site and in the museum. The famous copper deposit at Tsumeb in northern Namibia was closed as a mine in 1996, but in addition to commercial sales of blister copper, Tsumeb is noted for its mineralogical diversity, having provided innumerable specimens of unique or rare minerals to the world's museums. Tsumeb therefore also deserves to achieve the status of a geosite. Other locations in Namibia that are of geological significance include traces of Triassic dinosauromorpha at Otjihaenamparero in central Namibia; the Fish River Canyon in southern Namibia is the second largest canyon of the world and is famous for its scenic beauty.[19]
Hoba meteorite, the largest known intact meteorite
Aerial view of Weissrand (2019)
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See also
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References
- ↑ Kukulus, 2004, p.10
- ↑ Schluter, Thomas (2006). Geological Atlas of Africa (PDF). Springer. pp. 172–175.
- ↑ MME, 2011, p.1
- 1 2 3 4 5 6 Pickford, 1995, p.52
- 1 2 3 4 5 Negonga, 2014, p.6
- ↑ Borg, 1995, p.110
- ↑ Otjihaene-Maparero farm at Fossilworks.org
- ↑ Bogenfels at Fossilworks.org
- ↑ Elizabethfeld at Fossilworks.org
- ↑ "Roter Kamm crater". Archived from the original on 2016-03-04. Retrieved 2018-06-09.
- ↑ Tsumeb - Mindat.org
- ↑ Arsentsumebite - Mindat.org
- ↑ Tsumebite - Mindat.org
- ↑ Schluter 2006, p. 172.
- 1 2 Schluter 2006, p. 174.
- ↑ Kukulus, 2004, p.146
- ↑ Sakariassen, 2007, p.2
- ↑ Kukulus, 2004, p.149
- ↑ Schluter 2006, p. 175.
Bibliography
- Borg, G (1995), "Metallogenesis of Neoproterozoic basins in Namibia and Botswana" (PDF), Communications of the Geological Survey of Namibia, 10: 109–119, retrieved 2018-08-26
- Kukulus, Matthias (2004), A quantitative approach to the evolution of the central Walvis Basin offshore NW-Namibia: structure, mass balancing, and hydrocarbon potential (PhD thesis), Julius-Maximilians-Universität Würzburg, pp. 1–241
- MacDonald, Francis A.; Strauss, Justin V.; Rose, Catherine V.; Duda, Francis O.; Schrag, Daniel P. (2010), "Stratigraphy of the Port Nolloth Group of Namibia and South Africa and implications for the age of Neoproterozoic iron formations" (PDF), American Journal of Science, 310 (9): 862–888, Bibcode:2010AmJS..310..862M, doi:10.2475/09.2010.05, retrieved 2018-08-26
- Negonga, Martin (2014), Acreage portfolio of Namibian sedimentary basins (PDF), AAPG Annual Convention, pp. 1–31, retrieved 2018-08-26
- Pickford, Martin (1995), "Karoo Supergroup palaeontology of Namibia and brief description of a thecodont from Omingonde" (PDF), Paleontologica Africana, 32: 51–66, retrieved 2018-08-26
- Sakariassen, Rune (2007), North Namibia margin: regional tectonic evolution based on integrated analysis of seismic reflection and potential field data and modelling (MSc. thesis), University of Oslo, pp. 1–94, retrieved 2018-06-08
- Various, Authors (2011), The Geology of Namibia (PDF), MME, pp. 1–2, retrieved 2018-08-26
Further reading
- Dauteuil, Olivier; Picart, Carole; Guillocheau, François; Pickford, Martin; Senut, Brigitte (2018), "Cenozoic deformation and geomorphic evolution of the Sperrgebiet (Southern Namibia)" (PDF), Communications of the Geological Survey of Namibia, 18: 1–18, retrieved 2018-08-26
- Fenwick, Gordon A (1990), Origin and Surface Form of the Tsondab Sandstone Formation, Central Namib Desert (MSc. thesis) (PDF), University of Witwatersrand, pp. 1–128, retrieved 2018-08-26
- Jerram, Dougal A. (2000), "The Fossilised Desert: recent developments in our understanding of the Lower Cretaceous deposits in the Huab Basin, NW Namibia" (PDF), Communications of the Geological Survey of Namibia, 12: 303–313, retrieved 2018-08-26
- Mocke, Helke (2018), "The Fossil Collections from the Sperrgebiet at the National Earth Science Museum, Geological Survey of Namibia" (PDF), Communications of the Geological Survey of Namibia, 18: 124–131, retrieved 2018-08-26
- Pickford, Martin (2018), "Zegdoumyidae (Rodentia, Mammalia) from the Middle Eocene of Black Crow, Namibia : taxonomy, dental formula" (PDF), Communications of the Geological Survey of Namibia, 18: 48–63, retrieved 2018-08-26
- Pickford, Martin (2014), "New Ratite Eggshells from the Miocene of Namibia" (PDF), Communications of the Geological Survey of Namibia, 15: 70–90, retrieved 2018-08-26
- Pickford, Martin (2009), "Mio-Plio-Pleistocene geology and palaeobiology of Etosha Pan, Namibia" (PDF), Communications of the Geological Survey of Namibia, 14: 95–139, retrieved 2018-08-26
- Senut, Brigite (2000), "Fossil ratite eggshells: A useful tool for Cainozoic biostratigraphy in Namibia" (PDF), Communications of the Geological Survey of Namibia, 12: 421–428, retrieved 2018-08-26
- Werner, Mario (2006), The stratigraphy, sedimentology, and age of the Late Palaeozoic Mesosaurus Inland Sea, SW-Gondwana - New implications from studies on sediments and altered pyroclastic layers of the Dwyka and Ecca Group (lower Karoo Supergroup) in southern Namibia (PhD thesis) (PDF), Julius-Maximilians-Universität Würzburg, pp. 1–428, archived from the original (PDF) on 2018-08-29, retrieved 2018-08-26