Structural Style and Timing of Syrian Arc Deformation in Northern Egypt

By

 Adel R. Moustafa¹

(1) Ain Shams University, Cairo, Egypt

 Syrian arc structures form a NE-SW oriented belt of compressional features affecting the Mesozoic rocks in northern Egypt. They extend from N. Sinai to the NE part of the Western Desert in excellent exposures but gradually get buried westward where they are recognized in the subsurface. Integrated surface (field mapping) and subsurface (seismic and borehole) studies indicate the tectonic evolution of these structures and its effect on the hydrocarbon systems in northern Egypt. These compressional structures were formed by positive structural inversion of old extensional basins formed during the Jurassic and Early Cretaceous opening of the Neotethys. Although the early normal faults have a predominant ENE orientation, other trends are also common, e.g. NNE and WNW. The magnitude of inversion increases northeastward where total inversion is clear in northern Sinai. Inversion took place in several phases. It started mildly in the Turonian but was severe during the Campanian-Maastrichtian and late Middle Eocene phases. Many of the Syrian arc folds formed islands in the Eocene seas while the intervening (synclinal) areas witnessed continuous sedimentation. Positive structural inversion in response to WNW-ESE shortening due to the convergence between the Afro-Arabian and Eurasian plates reactivated the Early Mesozoic normal faults differently based on their orientation. Pure reverse slip reactivated the NNE-oriented faults whereas oblique-slip with dextral component reactivated the ENE-oriented faults. Late Cretaceous-Early Tertiary Syrian-arc shortening ended in the Oligo-Miocene time in northern Egypt by opening of the Gulf of Suez-Red Sea rift orthogonal to the Syrian arc compressional structures.