Rift Basin Sequence Stratigraphy: Some Examples from the Gulf Of Suez

Abstract

Unconformity-bounded sequences within the Miocene strata of the Suez Rift reflect a complex interplay between tectonism and sea level fluctuations. Analyses of Miocene outcrops along the Sinai margin of the Gulf of Suez provide new insights into the sequence stratigraphy of this basin. The Miocene strata can be subdivided into seven major sequences separated by biostratigraphically defined time breaks. These lacunae represent depositional sequence boundaries, transgressive surfaces and condensed sections. These basinwide time breaks were related to major tectonic events from rift initiation through rift climax, and post-rift stages. These events include regional sag and fault initiation, fault linkage, footwall uplift, shallowing of detachment depths and increased fault block rotations, regional isostatic uplift, and thermal subsidence. Superimposed on this complex structural evolution were Miocene sea level fluctuations of a magnitude of several tens of meters to a hundred meters. The Sinai outcrops expose the four oldest Miocene biostratigraphic sequences which correspond to two depositional sequences. The lower sequence consists of the Nukhul Formation which was deposited during a transgression (with the higher frequency events recorded as local erosional surfaces, flooding surfaces, and ravinements) and the Mheiherrat Formation which was deposited during a relative high stand. The upper sequence includes the Asl Formation which was deposited during a low stand and the Ras Budran Member of the Ayun Musa Formation which was deposited during the ensuing high stand.