Structural and stratigraphic evolution of the Gulf of Suez Rift, Egypt: a synthesis

The structural and stratigraphic development of the Gulf of Suez Rift reflects the interplay of five principal factors: (1) the presence of pre-existing fault systems, penetrative fabrics and basement terrane boundaries, (2) eustatic sea-level changes, (3) changes in basin connectivity to the Mediterranean Sea and Indian Ocean, (4) rapid changes in African intra-plate stress fields, and (5) activation of the Levant-Aqaba transform plate boundary. The Gulf of Suez Rift initiated in the late Oligocene, probably propagating northwards, and intersecting a major east-west structural boundary of late Eocene age at the latitude of Suez city. North of Suez, extension was more diffuse but mostly focused on the Manzala Rift that is presently buried beneath the Nile delta. Earliest syn-rift, mainly continental sediments (Chattian-Aquitanian) consisted of red beds containing minor basalts. Marine Oligocene strata are presently only proven from the southernmost Gulf, at the juncture with the northern Red Sea. By the Aquitanian, a shallow to marginal marine environment prevailed in most of the rift. The prolonged Burdigalian sea-level rise enabled marine waters to flow freely between the Mediterranean Sea and the Gulf of Suez, resulting in deposition of thick Globigerina shales and deep-water carbonates. During the Langhian and early Serravallian, rapid eustatic sea-level changes resulted in pronounced facies changes within the rift. During the late Serravallian significant fall in sea-levels, the Mediterranean water connection was either completely or intermittently blocked, leading to deposition of evaporites in the central and southern Gulf sub-basins. Thick halite sections accumulated in the late Miocene, and later loading resulted in the formation of salt diapirs and salt walls. Normal marine conditions were re-established during the Pliocene, but waters were then provided by the Red Sea-Gulf of Aden connection to the Indian Ocean, and a permanent land-barrier separated the Gulf of Suez from the Mediterranean. Analysis of fault geometries, fault kinematics and sedimentation patterns indicate that rift-normal extension predominated throughout the Oligocene to early middle Miocene evolution of the rift. In the middle Miocene, the Levant-Gulf of Aqaba transform boundary was established, linking the Red Sea Rift plate boundary to the convergent Bitlis-Zagros plate boundary. This resulted in a dramatic decrease in extension rates across the Gulf of Suez and a clockwise rotation of stress fields in Sinai. During the late Pleistocene, the intra-Gulf of Suez extension direction rotated counter-clockwise to N15degreesE.