AFRICA'S RIFTED MARGIN LITHOSPHERIC ARCHITECTURE

African rifted margins, which originated in 4 discrete episodes during the past 185 My, display great diversity resulting from interactions among a relatively small number of influences including: (1) Pre-rifting basement structure (2) Structure, age and degree of extension of the local intra-continental rifts on which the formation of ocean-floor has been initiated (3) Intra-continental-rift fill involving volcanic rocks, non-marine sedimentary rocks (including lacustrine organic-rich rocks) and marine sedimentary rocks (including evaporites) (4) Local and remote deep-sourced and shallow-sourced mantle plumes (5) Rapidly propagating cracks extending from plume eruption sites and localizing dike-swarms. These controls which dominated at times before ocean floor began to form continued to be influential later but once ocean floor began to form new influences included: (6) the development of wide seaward dipping reflector(wSDR) provinces (related to the locations of mantle plumes) and narrower( nSDR) provinces (related to the initiation of more normal ocean-floor) (7) the locations of transform faults and fracture zones, which have been important on all coasts, but dominant in the Gulf of Guinea, the south coast of Africa, the Maghreb and the Lindi coast.(8) Ocean-opening evaporites and their diapirism.(9) Erosion of rift shoulders (10) Deposition of marine carbonate rocks in regions starved of siliciclastic sediment (11) A concentration of siliciclastic sediments in deltas at the mouths of a small number of major rivers many of which have flowed along intra-continental rifts (12) Long-shore drift (13) Climatic variations, especially since the formation of the E. Antarctic ice-sheet at ca. 34 Ma leading to siliciclastic sediment starvation on desert coasts and intense erosion under the ITCZ (14) Eustatic sea level variations and (15) the occurrence of submarine canyons and the related evolution of deep-sea fan systems.