Gulf of Suez, Egypt

K. I. Schuetz

The Gulf of Suez is an intracratonic rift basin which originated in the early Miocene on the once-continuous Arabo-African plate. The Precambrian crystalline basement is overlain by a platform cover of Early Cambrian to Eocene age. There is no evidence of tectonic precursors to the Miocene breakup. Marine transgressions, for example during the Carboniferous and Cretaceous, followed wide embayments caused by long-wavelength oscillations trending northwest-southeast on the North African craton.

During the Oligocene most of the Gulf of Suez area was subaerially exposed and eroded, with the erosion cutting down to basement in the Red Sea area where only a thin sediment cover existed. The initial rifting approximately 22 m.y.B.P. was accompanied by basalt intrusions of sills and dikes in the gulf and by basalt flows from fissures several hundred kilometers away from the gulf in the Western Desert. Rifting in the Gulf of Suez occurred near sea level. After a short period of fluviatile and lacustrine sedimentation of the Nukhul Formation, the sea intruded the rift from the very beginning, as pillow basalts, marine foraminifers, and evaporites prove. Marine sedimentation continued with some continental influence from the graben edges. Extension and subsidence were almost continuous to the present, however, with varying amounts of subsidence and different tectonic expression in the subbasins. The initial rifting du ing the Aquitanian created relatively small faults and fault blocks. During the Burdigalian and Langhian (Rudeis and Kareem Formations) subsidence and faulting increased, resulting in larger and more tilted fault blocks. In the Serravallian the extension was big enough that it decoupled the Sinai from the African stress system and the whole gulf subsided, controlled mainly by the faults at the graben shoulders. This created the wide evaporite basin of the South Gharib and Zeit Formations.

The northernmost basin, the Darag basin, was not affected during the Serravallian by the decoupling and did not subside much. Only after the Miocene did the rotational opening of the gulf allow the Darag basin to subside fast again in Pliocene to Holocene time.

Since the beginning of the Miocene the central parts of the rift have subsided 6-7 km, which is about one-third of the thickness of the continental crust. The uplift of the rift shoulders ranges from a few meters in the north to approximately 2-3 km over most of the length of the rift, thereby creating a north-plunging basement. Uplift of the graben shoulders started early, and some locally restricted basement outcrops existed relatively early in Burdigalian/Langhian (e.g., at Gebel Zeit and east of the Belayim and Morgan fields). However, large areas of basement were eroded only during the Pliocene.

The extension is interpreted to be normal to the rift (with only a very small and probably episodal right-lateral component). In general Miocene faulting created a new set of fault directions; however, in some cases an older Jurassic "structural grain" was followed. The older fault directions often offset clysmic faults, thereby creating "compartmented" fault block units. Similar long fault block units with offsets by the Miocene Gulf of Aqaba system are obvious on the Sinai side.

Research in the extensional regime produced several models, updoming, stretching, etc. These models, including the more recent ones, do not fit very well with the observed facts of the individual characteristics of the different subbasins, especially the north-south differentiation, as well as the geologic evolution of the Gulf of Suez through time. A combination of doming and nonuniform stretching seems more appropriate for the Gulf of Suez.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.