Rift Climax Synrift Sedimentation in Major Rift Accommodation Zones: The Wadi Gharandal - Gebel Gushea Area, Miocene Suez Rift, Egypt

Paul Woodman, Rob Gawthorpe, and David Hodgetts
The University of Manchester, Manchester, United Kingdom

Within extensional basins, large scale normal fault bounded blocks, approximately 15-20km wide by 20-30 km long provide a first order control on the variability of synrift sediment deposition. Previous studies have improved the current understanding of deposition around segmented normal faults and within relay ramps, however, there has been little examination of the controls on sedimentation in rift-wide accommodation zones where the polarity of major block-bounding fault changes. This sudy uses onshore exposures at the margin of the Zafarana accommodation zone to address sedimentation in an area of fault polarity change.

The study focuses on Miocene, synrift sequences deposited in the structurally diffuse area between the Hamman Faraun and Sudr fault blocks, located on the western margin of the Suez Rift, Egypt. We characterise the variabiltiy in sedimentology and sequence stratigraphy using a combination of traditional field studies and digital outcrop techniques (DGPS and LIDAR) to produce process-based depositonal models for the synrift succession.

The study highlights the primary importance of a complex structural template on facies and thickness distributions associated with intra-block faults, syn-sedimentary growth faults, and fault-related folding. However, the distributed deformation in the accommodation zone results in subtle topography and shallower bathymetry compared to the major fault blocks in the adjacent northern and central dip provinces. This reduced topography in the accommodation zone results in a stronger relative sea-level signal compared to the hangingwalls of the main block-bounding faults.