The Tectonic Evolution of Red Sea and Gulf of Aden

ALLEN, R. B., Earth Science and Resources Institute, University of South Carolina, Columbia, SC, A. G. ABOUZAKHM, Consultant, Zamalek, Cairo, Egypt, and A. H. SIKANDER, The World Bank, Washington, DC

The Red Sea and Gulf of Aden, formed by rifting of the Arabian plate away from Africa, have been the subjects of numerous studies since the 1960s. Geophysical and geologic data gathered during hydrocarbon exploration by several companies are being synthesized as part of the World Bank-executed Red Sea/Gulf of Aden Regional Hydrocarbon Study Project. This synthesis provides an opportunity to study the regional variation in tectonic history and structural style within the two basins, particularly toward the basin margins, where data coverage is most complete and a thinner sedimentary cover allows more reliable interpretation of deeper horizons.

Based on this data, most of the Red Sea shows a similar tectonic history to that of the Gulf of Suez. Widespread normal faulting developed contemporaneous with deposition of a dominantly clastic sequence of Oligocene(?) to middle Miocene age. The faulting often dies out within or below thick middle to upper Miocene evaporite deposits with only few faults affecting the younger units. The pattern of faulting suggests that extension in the Red Sea has become concentrated along the axial trough, and possibly along a northern extension of the Danakil Depression in Ethiopia, since approximately the middle to late Miocene. Structures throughout the Oligocene-Holocene evolution of the Red Sea show a predominant northwest-southeast orientation, parallel to the basin axis. Segmentation of the R d Sea by transverse structures affects the drainage pattern on the western margin, and thus the development of post-evaporite depocenters.

The Gulf of Aden, on the other hand, shows a strong contrast between largely west-northwest-east-southeast oriented extensional structures on land, and generally more east-west oriented extensional structures on the continental shelves and slopes. The onshore extensional

structures oriented oblique to the coast, and approximately perpendicular to transform fault trends in the oceanic crust of the central Gulf of Aden. This contrast is extensional structure orientations has important implications for the tectonic evolution of the Gulf of Aden.

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)