Print this pagePrecambrian Fractures of the Gulf of Suez, Egypt, and Its Role In the Miocene Rifting
YOUNES, AMGAD I., KEN McCLAY, and TERRY SPELL
Analysis of Landsat images, outcrop and well log data shows that faults and fractures in the Gulf of Suez cluster around north-south and northwest trends, both which are associated with Precambrian north-south and northeast compression respectively. Ar{40}/Ar{39} dates of northwest-oriented, fracture-filling dikes yield 554 +/- 2 Ma. North-south fractures dominate the Older granites (577 +/- 2 Ma) whereas the northwest fractures dominate the Younger granites (476 +/- 2 Ma) which were emplaced during NW extension accompanied by rift-parallel, rhyolitic dike intrusions (503 +/-2 Ma). This extension remained until the Late Cambrian when both trends were reactivated forming longitudinal basins in which the Nubia Sandstone deposited.
During the Miocene, N60 degrees E extension reactivated both trends simultaneously such as the northwest trends were dominated by dip-slip movements, and the north-south trends were dominated by left-lateral oblique-slip components. The intersection of both trends divided the rift into rhomboidal basins, and determined the plunge direction (depo-center) of the fault blocks: either into the obtuse angle of intersection or, less commonly, away from the acute angle. The north-south trend, being unfavorable for extension, was utilized as transfer zones and relays connecting the north-west segments. Within a fault block, older northwest fabric distributed the deformation into discrete fault throws which rarely exceed 1 m. In contrast, north-south faults occur in localized zones which can be matched across the Gulf of Suez rift and along the Red Sea coast. Major north-south fault zones in the Gulf of Suez occur at the tips of the trans-rift accommodation zones and perhaps have controlled their locations.