Determining the Depositional Controls on Rift Axis, Synrift Deposits: the October Fault Block, Gulf of Suez Rift, Egypt

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

Within extensional basins, the location and nature of synrift depositional systems reflects a complex interaction of controlling factors. Interacting with the spatial and temporal evolution of the localised structural template are the more regional controls of changes in eustasy and sediment supply, resulting in complex and highly variable sedimentology and stratigraphy within synrift megasequences.

Utilising an extensive subsurface database comprising wireline logs, biostratigraphy and core for the Miocene, synrift Asl and Hawara Formations deposited adjacent to and upon the October fault block within the axial part of the Suez Rift, Egypt, we characterise the primary sedimentology and stratigraphic framework to develop process based depositional models and stratigraphic unit based isopachs, thereby highlighting the nature of major facies and thicknesses variations. When related to the present day structural configuration derived from seismic, these variations reveal the sequential structural and palaeogeographic evolution of the October fault block.

This study demonstrates that in axial rift settings, localised faulting is episodic and the main focus of displacement varies spatially through time, resulting in marked variations in active sediment transfer pathways and depocentres. Furthermore that despite the marked variations in topography and resultant deeper bathymetry associated in hangingwalls to major bounding faults than those in marginal rift settings, significant variations in eustatic sea level may still be identified and that coupled with the regional nature of the structural dip province, may produce variations in the active sediment source and resultant depositional system.