Rift Border Fault System Evolution and Impact on Sedimentation, Southwestern Gulf of Suez, Egypt

By

 Mohamed S. Ahmed¹, Adel Sehim¹

(1) Cairo University, Cairo, Egypt

 The Gulf of Suez is a major petroliferous basin in Egypt. Poor seismic attributes of sequences underlying thick Miocene salts gave importance in studying the surface structural architecture and rift-sedimentation aiming at reaching better subsurface image. The Southwestern rift-segment is selected in this study where numerous hydrocarbon fields exist in vicinity and few works are published. Detailed field analysis and mapping revealed multi-storied fault developments in time and space with variable impact on sedimentation.

Two major interbasinal accommodation zones are delineated with extension in basement rocks of the rift shoulder as Precambrian shear zones and imbricate-thrust system. The rift border fault system bounds the rift and is represented by linked short segments of 4-7 km long. Several fault-segments propagated in one direction showing maximum displacement at one fault tip. Hard-linkage transfer faults connect fault tips of variable magnitudes.

Differential evolution of fault-segments had a great impact on rift-sedimentation. Entrapment of early-rift sediments adjacent to some faults indicates early-rift fault development whereas divergent sedimentary-wedging away from other faults refers to deposition on flexure-zone above a blind fault. Deposition of younger sequences adjacent to fault planes prove later fault-ruptures.

The differential fault development and along-strike displacement variations are reflected on the rift shoulder paleoslopes. Channel reservoir clastics derived from the shoulder into the rift basin across trap-door transfer faults.