Geophysics and the Crustal Structure of West Africa

West Africa, facing the Laurentian basement of North America and the Brazilian craton of South America in a Bullard-type predrift reconstruction, is largely identified to the West African craton (a Precambrian granitized basement) and its surrounding Upper Proterozoic (Pan-African) mobile belts. In contrast with relatively complete geological studies (Fabre 1983), West Africa did not benefit from a large number of extensive geophysical studies. Only gravity measurements have resulted in a nearly complete regional mapping and thereby are useful for investigation of the crustal structure and clarification of geological interpretation. In places, seismological studies such as the detection of teleseismic travel time anomalies or surface waves velocity dispersion measurements, magnetotelluric soundings, and heat flow measurements have been made. Considering the total absence of deep seismic profiles, all these data furnish a precious adjunct to the knowledge of the crustal and upper mantle structures of West Africa.