A PLATE TECTONIC SETTING FOR MESOZOIC RIFTS OF WEST AND CENTRAL AFRICA

Africa, by virtue of its central position within Gondwana, has recorded much of the complex history of plate interactions which have progressively fragmented this supercontinent since the Early Mesozoic. Continental reconstructions reveal both a temporal and spatial relationship between the development of the continental margins of Africa and the formation of rifted sedimentary basins deep within the African continent. The multi-stage opening of the Atlantic Ocean and associated rifting in West and Central Africa provide one of the most impressive examples of ocean-continent tectonic interactions. During the Early Cretaceous the onset of rifting along the future margins of the South Atlantic is contemporaneous with intra-continental rifting generating both strike-slip and extensional basins within West and Central Africa. The syn-rift phase of intra-continental basin development continued until the Santonian, by which time Africa and South America had been physically separated for approximately 10 Ma. Except for minor rifting during the Senonian and Tertiary, the short-lived phase of deformation at about 80 Ma marks the transition into the post-rift or "sag" phase of basin development. This deformational event can be correlated with a period of plate motion changes, recognised from fracture zone geometries, seen in both the Central and South Atlantic oceans. Using present day stress analogies, Cretaceous rifting in Africa can provide a means of indicating the regional palaeostress directions within Africa at this time.