West African Craton

The West African Craton is one of the five large masses, or cratons, of the Precambrian basement rock of Africa that make up the African Plate, the others being the Kalahari craton, Congo craton, Saharan Metacraton and Tanzania Craton. These land masses came together in the late Precambrian and early Palaeozoic eras to form the African continent. At one time, volcanic action around the rim of the craton may have contributed to a major global warming event.

The craton appears to have formed when three Archean cratons fused: Leo-Man-Ghana, Taoudeni and Reguibat. The first two docked around 2.1 Ga (billion years ago), and the Reguibat Craton docked with the craton around 2 Ga. The roots of the combined craton extend to a depth of over 300 km in the sub-continental lithospheric mantle.

The West African Craton stretches from the Little Atlas mountains of Morocco to the Gulf of Guinea, and is bounded by mobile belts of much younger rocks to the north, east and west. The oldest rocks were metamorphosed 2.9 to 2.5 billion years ago. In the Sahara they are mostly covered by more recent sediments from the Phanerozoic Eon. Further south, younger volcanic and sedimentary rocks outcrop in Ghana, Ivory Coast, and Sierra Leone, surrounded by even younger sediments laid down in the Precambrian.

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