Neotectonics of the Red Sea, Gulf of Suez and Gulf of Aqaba

Abstract

The Red Sea, Gulf of Suez, and Gulf of Aqaba comprise the active plate boundaries that separate Africa-Nubia, Arabia and Sinai. This tripartite configuration has been in existence since the Middle Miocene, or about the past 12–14 Ma. We describe the ongoing and geologically recent tectonics of these regions. The Red Sea rift lies east of a broad region of E-W maximum horizontal stress (S_Hmax) that covers much of central Africa-Nubia. On its Arabian side, S_Hmax is oriented N-S to NE-SW. These far field stresses owe their origins to the spreading centres of the Atlantic Ocean and collision between Arabia and Eurasia along the Bitlis-Zagros suture. At the continental scale, the Red Sea is therefore subjected to compression perpendicular to or at a high-angle to its margins. The realm of shallow crustal stresses conducive to extensional faulting in a Red Sea orientation (rift-normal S_hmin) is presently restricted to the Red Sea marine basin itself, and perhaps narrow belts along its shoulders. In the Gulf of Suez there is enough data to show that each of its sub-basins is presently undergoing extension, but in conjunction with differently oriented, sub-regional shallow crustal stress fields. These appear to be spatially related to the original Early Miocene syn-rift basin geometries. NNE-SSW extension in the southern Gulf of Suez is probably generated by sinistral slip on the similarly oriented Gulf of Aqaba transform margin. Large M > 6 earthquakes are generally restricted to the central basin of the Gulf of Aqaba, the southern Gulf of Suez, and the greater Afar region. The geodynamic details responsible for the focusing of these large events are specific to each locale but all are in general associated with the junctions of major plate boundaries. Catalogues of earthquake activity and GPS datasets show that the Sinai micro-plate is still moving away from Africa with a component of left-lateral slip. This results in components of extension perpendicular to both the Gulf of Suez and the Gulf of Aqaba. The kinematics of the southern Red Sea are similarly complex. Not all opening has jumped to the west side of the Danakil horst and significant tectonic activity still occurs along the southernmost Red Sea axis in the vicinity of the Zubair Archipelago. This is the only volcanically active segment of the Red Sea basin that is above sea level. Dike intrusions are ~N-S and not aligned parallel to the rift axis and may indicate that the underlying magmatism is swinging to the west to link with the Afar triple junction. All of the margins of the Red Sea, Gulf of Suez and Gulf of Aqaba underwent tectonically-driven rift shoulder uplift and denudation in the past, particularly during the main phases of continental rifting. However, during the past 125 kyr uplift has been focused along the footwalls of a few, active extensional faults. These include the Hammam Faraun-Tanka fault in the central Gulf of Suez, the Gebel el Zeit-Shadwan Island fault in the southern Gulf of Suez, the Sinai and Arabia coastal boundaries of the Gulf of Aqaba, and faults at Tiran Island at the junction of the Gulf of Aqaba and northern Red Sea. Smaller-scale extensional faulting is also occurring along the Saudi Arabian margin of the northern Red Sea, in the Dahlak and Farasan Archipelagos, and on the volcanically active islands of the Zubair Archipelago in the southernmost Red Sea. On the Farasan and Dahlak islands this is largely related to the movement of underlying salt bodies, similar to effects documented along the coastal plain of Yemen. Though not active at the present time, a broad belt of small-offset, very linear extensional faults dissected the western margin of the central Gulf of Suez during the Plio-Pleistocene. Similar age and style deformation has not been identified in the Suez sub-basins to the north or south. The most significant large-scale neotectonic features of the Red Sea rift system are its southern oceanic spreading centre and the northern linkage to the left-lateral Gulf of Aqaba—Levant transform fault. However, many segments of the rift margins and in particular the Gulf of Suez remain tectonically active. These areas provide stress field and horizontal and vertical displacement data that are relatively inexpensive to acquire and complementary to analyses of the offshore main plate boundaries themselves.

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