Deep-ocean basins and submarines rises off the continental margin of south-eastern Africa: new geological research

Some conclusions from deep-sea survey carried out in the Transkei Basin and Natal Valley off the SE coast of South Africa are reported. The continental margin is of the "sheared' type, ie it formed during the progress of strike-slip faulting as the South American plate drifted away from Africa. The deep extensional basins that develop along major strike-slip faults can provide the ideal restricted depositories for organic-rich muds which are later transformed into shales. Hydrocarbons are generated under heat and pressure, and oil and gas deposits may be laid down. Plate reorganisation and the origins of "microcontinents' are discussed, as are sea-level fluctuations, ocean currents, sedimentation and global change. Tectonic extensions of the East African rift systems are noted. -P.J.Jarvis