Abstract

Wilson's concept that transform faults were initiated along ancient fractures is supported by evidence from southeastern Egypt. Geophysical and geological investigations have outlined blocks bounded by transverse fractures oriented perpendicular to the Red Sea, linear anomalies parallel to the Red Sea due to deep-seated tholeiitic dikes, and shear zones related to left-lateral movement along the Red Sea. Similar features occur in Saudi Arabia. Consideration of bathymetric data and matching of structural features across the Red Sea indicate that left-lateral movement of 75 to 80 km occurred in Late Cretaceous to Eocene time during the opening of the Gulf of Aden, predating the ocean-floor spreading in the Red Sea in late Eocene time. The direction of the Red Sea spreading was guided by continental Precambrian fractures trending east-northeast that extended offshore into transverse tectonic structures on which deposits of metalliferous sediment are located. It is postulated that later Red Sea extension occurred in late Miocene to early Pliocene time and from 3 m.y. B.P. to the present and that the Sinai block moved in a left-lateral direction about 25 km along the Gulf of Suez fault from its original position during the three main periods of ocean-floor spreading.

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