Structural characteristics and tectonic evolution of the east-margin blocks of the Suez rift

Abstract

Detailed field study of the east-margin blocks of the Suez rift indicates that rift initiation was marked by 22-24 Ma old volcanicity followed by second-order (relatively small) extensional faulting without block rotation. Slight rotation of first-order (large) rift blocks took place shortly before or during the deposition of the earliest rift sediments (Nukhul Formation). The shallow-water environment of deposition of the Nukhul Formation became deeper during the deposition of the overlying Rudeis Formation in response to rapid tectonic subsidence. A major event (mid-clysmic, 17 Ma ago) led to the rejuvenation of many faults bounding the large rift blocks, the development of several intra-block faults, and an abrupt change in the environment of deposition. At that time, tectonic deformation increased towards the rift axis where the width of the active part of the rift decreased. As a result of this mid-clysmic event, coarse elastics were deposited close to the major faults; later these deposits were faulted in a younger event. NW-NNW (clysmic) and N-NNE (transfer) faults are the two predominant normal fault sets in the east-margin blocks and link up in a characteristic zig-zag pattern. Block rotation is related to slip on NW-NNW listric faults. Fault plane slickenside lineations indicate predominant NE-SW extension as well as a subordinate E-W to ESE-WNW extension. The latter is perhaps related to post-Miocene mild deformation. Slip on the major faults of the rift is associated with drape folding and footwall deformation. Both lead to the development of rift-facing monoclines. The deformed parts of the footwall are spindle-shaped and link to the main faults via N-NNE transfer faults. Footwall deformation also results where a major fault bends out leaving a protrusion of the footwall. Rift extension is transferred beyond the rift boundary via some transfer faults and affects some parts of the shoulder. © 1993.