Basin Evolution and Geochemical Modeling
Sedimentology and Sequence Stratigraphy of Late Syn-rift Tidal Sediments; The Asl Formation, Suez Rift, Egypt
Research by Dr Ian Carr and Professor Rob L. Gawthorpe
Introduction:
The Miocene aged Asl Formation was deposited on the ramp-like hangingwall dipslope of the western limb of the El Qaa Syncline during rift climax times. The sedimentary package has been divided into four Lithofacies consisting of a shallowing upward succession from offshore shelf mudstones, offshore transition mudstones and sandstones, bioturbated lower shoreface sandstones and tidally cross-bedded sandstone.
Summary:
Key surfaces were recognised by abrupt down-dip or up-dip shifts in facies tracts. These surfaces have been used to divide the succession into six sequences. The character of each key surface and individual systems tracts can be documented in detail in updip and downdip localities for >10 km along strike. During the deposition of the six shallow marine sequences of the Asl Formation a transfer zone was located just south of the study area, through which tidal currents were funnelled through during times of sea-level lowstand. In the hangingwall dipslope locality Asl Formation deposition was affected by interaction between hangingwall subsidence associated with the Baba-Sidri and Hadahid faults to the east, and footwall uplift of the Nezzazat and Abu Durba faults to the west, in a position where subsidence and uplift rates were low. Within the whole Asl succession there is an overall tectonic control on sequences, they expand down structural dip, they decrease in structural dip vertically through the succession and the tidal units are funnelled through the transfer zone. However, in marked contrast to studies along major border faults, regional or global sea-level changes had a major impact on the high frequency sequence stratigraphy of the hangingwall dipslope succession.