McCLAY, KEN, Arco Professor of Structural Geology, Royal Holloway, University of London, UK
Abstract: Tectonic Evolution of the Red Sea and Gulf of Suez Rift Systems
The northern Red Sea and Gulf of Suez rift system is the northwestern termination of the northwest arm of the Neogene Gulf of Aden, northern Ethiopian, and Red Sea rift systems formed by the north-northeastward separation of the Arabian plate from the African plate. The onshore northern Red Sea margin and the flanks of the Gulf of Suez provide some of the best exposed examples of rift fault systems and associated syn-extension marine sedimentation in the world. The Gulf of Suez is a major hydrocarbon province with several giant oil accumulations trapped in extensional fault blocks within the rift basin. The northern Red Sea-Gulf of Suez rift system is developed on Pan African igneous and metamorphic basement with a thin, pre-rift, Phanerozoic- Mesozoic-Paleogene sedimentary cover. Preexisting fault systems, basement fabrics, and basement terrane boundaries have exerted a strong control on the Neogene rift architecture.
The northern Red Sea and Gulf of Suez rift system is characterized by northwest- and north-northeast-trending rift border and intra-rift extensional faults that form distinct rhomboidal patterns. Rifting initiated in the Late Oligocene- early Miocene (Chattian-Aquitanian) with the formation of thin, generally continental red beds, accompanied by volumetrically minor basaltic volcanism. In Aquitanian times the sedimentation was dominantly shallow to marginal marine--generally coarse-grained conglomerates and sands at the rift margins and finer grained mudstones and marls toward the center of the rift. In detail, individual fault blocks within the rift experienced different structural and stratigraphic evolutions. The greatest syn-rift sedimentation occurred in the Burgidalian (the so-called rift climax) with thick accumulations of Globigerina marls and shales in the central rift basins. In the late Serravallian the rift sub-basins became isolated from open-ocean circulation and thick evaporite deposits were formed. In the Pliocene to Holocene normal marine conditions prevailed with connection to the Indian Ocean via the Red Sea-Gulf of Aden.
The extensional fault systems of the northern Red Sea-Gulf of Suez are spectacularly exposed along the rift margins. Basement cored domino-style tilted fault blocks occur in four distinct dip domains from the northern Red Sea into the Gulf of Suez. Complex accommodation zones separate these dip domains. Individual faults, both at the rift borders and within the rift, consist of linked segments. Overlapping faults form relay-ramp structures, and transfer faults are formed where relay ramps are broken along preexisting basement fabrics. Evolutionary models are proposed for the development of the northern Red Sea and Gulf of Suez fault systems. Structural styles within the Red Sea and Gulf of Suez rift are compared and contrasted with the results of scaled analog models and with extensional fault systems in the east African and North Sea rifts.
AAPG Search and Discovery Article #90922©1998-1999 AAPG International Distinguished Lectures