Mid-Clysmic Event, Gulf of Suez Rotational Deformation Associated with a Deep Crustal Detachment Fault

P. L. Vigano, T. L. Patton

Dip relationships at the boundaries of three stratigraphic packages (one prerift and two synrift) in the Gulf of Suez suggest that the early stages of structural development in the Gulf of Suez can be subdivided into two phases. Synrift sediments deposited in the first phase of deformation (prerotation units) demonstrate only minor angular discordance with the underlying pre-Miocene (prerift stratigraphy). Synrift sediments deposited in the second phase of deformation (rotation units) show marked angular discordance and onlapping relationships with underlying units.

We propose that the prerotation units were deposited during a period of basin-wide, generally vertical subsidence which was accommodated by slip on numerous, oppositely dipping normal faults. As subsidence continued, faults with similar dip directions began to work in unison and dominate the deformation of portions of the rift, causing faults with other orientations to play a lesser role or to become inactive. Minor rotations occurred during this phase of deformation. The rotational phase of deformation initiated as major faults propagated downward to and merged with a major detachment surface at depth. As extension continued, rotation of large, fault-bound blocks along deep-seated listric faults resulted in the exposure and erosion of both pre-Miocene and prerotation units along the pdip segments of the blocks. Sediments deposited during the rotational phase of deformation transgressed the backs of these rotated blocks and were laid down in angular discordance with the underlying units.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.