Structural styles associated with accommodation zone terminations within the western Gulf of Suez rift, Egypt.

摘要

A model based on field mapping is presented for the development of Neogene structures associated with accommodation zones in the western Gulf of Suez rift. The structural styles evolved in response to two episodes of coincident extension perpendicular to the rift axis, that were applied to a mechanically inhomogeneous stratigraphic succession. Brittle basement and Nubian lithologies are cut by high-angle normal faults which are deflected to shallower flats and ramps in the interbedded ductile and brittle Cenomanian to Eocene prerift platform succession. Folding within platform units in the hanging-walls range from open monoclines to recumbent anticlines with increasing throw on the underlying faults. These styles propagate through the synrift stratigraphic succession, but are complicated by the rapid lateral variation in mechanical character of the sedimentary packages and by halokinetic structures.;The two areas studied lie on the termination of accommodation zones against the western rift shoulder. These accommodation zones separate opposing tilt-block dip domains above low-angle basal detachments, also with opposing dips. The basal detachment surfaces deflect up into high-angle oblique and orthogonal ramps in the accommodation zones, permitting differential rotation and displacement between tilt-block domains to occur in a manner analogous to transfer faults. This ramping results in structural highs within the rift and offsets in the rift margin at accommodation zone terminations.;Faulting has separated the crust within the rift into discrete blocks delineated by Gulf-parallel normal faults and by Gulf-orthogonal and -oblique transfer faults. The blocks have been tilted over Gulf-parallel synthetic and antithetic normal faults which, by inference, sole into a basal detachment. Transfer faults, which also sole into the basal detachment, terminate the blocks along strike and accommodate the differential rotation and displacement between blocks.