Post-Miocene sedimentation and rift dynamics in the southern Gulf of Suez and northern Red Sea

Abstract

Field studies and seismic profiles along 400 km of the Egyptian coast cover important segments of the north- ern Red Sea and Gulf of Suez rift. Because the post- Miocene (Pliocene) coincides with the partial oceanization of the Red Sea as a consequence of transform movements along the Aqaba fault system, the region and stratigraphic level considered are keys to the understanding of rift evolution. The considerable thickness (1000 m) of constant shallow-marine post-Miocene sediments indicates continued post-Miocene subsidence. Within this general context, three distinct regions are recognized, each characterized by a specific tectonic and post-Miocene sedimentary record.

• 1. The northern and central parts of the Gulf of Suez are characterized by relatively homogeneous terrigenous and evaporitic sedimentation undisturbed by post- Miocene tectonics.

• 2. The southern Gulf of Suez, between the Morgan accommodation zone and the Aqaba transform, on the contrary, exhibit marked lateral variations between siliciclastics and carbonate sedimentation. These changes are controlled by reactivation of Miocene fault blocks and related diapirism of the Middle to (?)Late Miocene evaporites. In addition, spectacular southward gravity sliding on the evaporite substratum, facilitated by the accommodation space created by the opening of the Red Sea, has led to extensional collapse and formation of secondary post-Miocene basins north of the Aqaba transform zone.

• 3. The northern Red Sea also includes numerous post-Miocene movements, both parallel and oblique to the axis of the rift, relating to rejuvenated Miocene faults and evaporite remobilization. These movements, in common with the Gulf of Suez, occur on a local scale. However, unlike the Gulf of Suez, the post-Miocene series is also affected by a regional dip toward the axis of the rift and by the frequent discharges of basement- derived conglomerates, these structural and sedimentary features reflecting the opening of the Red Sea and uplift of the rift periphery.

The post-Miocene sediments indicate that the north- ern Red Sea has attained a post-rift, passive margin stage, that the southern Gulf of Suez, affected by recent extensional movements, has not yet attained this post- rift stage, while the central and northern parts of the Gulf of Suez are still tectonically stable.