Lake Bosumtwi Impact Crater

Ghana

Aerial overview of the Bosumtwi impact structure, Ghana.

Geological Period

Pleistocene

Main geological interest

Impact structures and extraterrestrial rocks
History of geosciences

Location

Ashanti Province, Ghana
06°32’00”N, 001°25’00”W

Aerial overview of the Bosumtwi impact structure, Ghana.

Bosumtwi is the youngest well preserved complex impact structure known on Earth and the source of the Ivory Coast tektites.

The Bosumtwi impact crater in Ghana is arguably the best-preserved complex young impact structure known on Earth. It displays a pronounced rim and is almost completely filled by Lake Bosumtwi, a hydrologically closed basin. It is the source crater of one of the four traditional tektite strewn fields, the Ivory Coast field. Besides being of local spiritual interest, the crater lake contains sediments that document the regional paleoclimate of the last million years, and it is a economic source of fish and tourism. It is a striking geographical feature with potential for outreach and education.

Outcrop of polymict impact breccia (suevite) north of crater rim at Bosumtwi.

Bosumtwi is the largest young impact structure currently known on Earth and is associated with one of only four known tektite strewn fields, the Ivory Coast field. It has an age of 1.07 Ma and a rim to rim diameter of about 10.5 kilometers. Bosumtwi is located in the Ashanti Region of Ghana. The Ivory Coast tektite strewn field extends beyond the land, as microtektites have been found in deep-sea cores off the coast of West Africa. Age and geochemical data confirm that these tektites were generated in the Bosumtwi impact event.
The well-preserved complex impact structure displays a pronounced rim, is almost completely filled by the Lake Bosumtwi, which has a diameter of ca. 8.5 kilometer. It is surrounded by a slight near-circular depression and an outer ring of minor topographic highs about 20 kilometers in diameter. The crater is excavated in 2 Ga old metamorphosed crystalline rocks. The first suggestion that Bosumtwi might be of impact origin came in 1931, and confirming evidence has been described from the 1960s in studies of high-temperature minerals, shock metamorphism, and meteoritic components in impact rocks and tektites. The lake sediments contain an important 1-Myr paleoclimatic record. The crater was extensively drilled in 2004.

Bosumtwi has been scientifically studied for almost a century and was the location of a major International Continental Scientific Drilling Program (ICDP) drilling project in 2004, for sediment (paleoclimate) and impact research. It is one of only 20 confirmed impact structures in Africa, and one of the best preserved.

Geological Map of the Bosumtwi impact crater area.

Ferrière, L. et al. (2008) ‘Shock metamorphism of Bosumtwi impact crater rocks, shock attenuation, and uplift formation’, Science, 322(5908), pp. 1678–1681. Available at: https://doi.org/10.1126/science.1166283.

Jones, W.B., Bacon, M. and Hastings, D.A. (1981) ‘The Lake Bosumtwi Impact Crater, Ghana’, Geological Society of America Bulletin, 92, pp. 342–349. Available at: https://doi.org/10.1130/0016-7606(1981)92<342:TLBICG>2.0.CO;2.

Koeberl, C. et al. (1998) ‘Petrology and geochemistry of target rocks from the Bosumtwi impact structure, Ghana, and comparison with Ivory Coast tektites’, Geochimica et Cosmochimica Acta, 62(12), pp. 2179–2196. Available at: https://doi.org/10.1016/S0016-7037(98)00137-9.

Koeberl, C. et al. (2007) ‘An international and multidisciplinary drilling project into a young complex impact structure: The 2004 ICDP Bosumtwi Crater Drilling Project – An overview’, Meteoritics and Planetary Science, 42(4–5), pp. 483–511. Available at: https://doi.org/10.1111/j.1945-5100.2007.tb01057.x.

MacLaren, M. (1931) ‘Lake Bosumtwi, Ashanti’, The Geographical Journal, 78(3), pp. 270–276. Available at: https://doi.org/10.2307/1784899.

Talbot, M.R. and Johannessen, T. (1992) ‘A high resolution palaeoclimatic record for the last 27,500 years in tropical West Africa from the carbon and nitrogen isotopic composition of lacustrine organic matter’, Earth and Planetary Science Letters, 110(1), pp. 23–37. Available at: https://doi.org/10.1016/0012-821X(92)90036-U.

Christian Koeberl.
University of Vienna. Austria.

Aaron Cavosie.
Curtin University. Australia.

David Baratoux.
Research Institute for Development, Geosciences Environment, Toulouse. France.

Daniel Kwadwo Asiedu.
University of Ghana.

Marian Selorm Sapah.
University of Ghana.

Yvonne Sena Akosua Loh.
University of Ghana.

Daniel Kwaku Boamah.
Ghana Institution of Geoscientists.

Prosper Mackenzie Nude.
University of Ghana.

Samuel Boakye Dampare.
Ghana Atomic Energy Commission.

Emmanuel Atuobi Agyekum.
Ghana Institution of Geoscientists.

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Lake Bosumtwi Impact Crater

Ghana

Geological Period

Main geological interest

Location

Bosumtwi is the youngest well preserved complex impact structure known on Earth and the source of the Ivory Coast tektites.

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