Chapter 20 - Regional tectonics and basin formation: the role of potential field studies – an application to the Mesozoic West and Central African Rift System

Abstract

There is now excellent terrestrial gravity data coverage over most of the world’s continents and an even better satellite-derived gravity coverage over the oceans to allow reliable investigation of tectonic structures of continental scale. On the other hand, Terrestrial magnetic data are generally patchier in their coverage. These data types are used here in an integrated study to investigate the development of the Mesozoic West and Central African Rift System (WCARS) that split Africa in two from the Nigeria coast in the west to the Kenya coast in the east. The rift system consists of a set of interconnecting rift basins linked by shear zones that are temporally and spatially related via the Benue Trough to plate tectonic processes that formed the Atlantic Oceans. These tectonic processes are best observed in the fabric and texture of the sea-floor bathymetry and mapped using the satellite-derived free-air gravity field. The age of the sea-floor structures can be determined from the geomagnetic reversal times recorded in the oceanic rocks. These data show that the Central Atlantic Ocean plate has undergone systematic changes in plate motion that has controlled the stress field of Africa, causing periods of extension, shear and compression deformation to affect the WCARS.