Structural setting of the central part of the Cairo-Suez District

Abstract

Detailed field mapping and structural study of the central part of the Cairo-Suez District was achieved as a second step in the detailed study and mapping of the whole Cairo-Suez District. Three sets of predominantly normal faults affect the exposed rocks of the study area and are oriented E-W, NW, and NNW. The E-W and some of the NW faults have a left-stepped en echelon arrangement in five E-W elongated belts which are proposed to overlie E-W deep-seated faults. The NW faults form a pervasive structural grain in this part of the Cairo-Suez District. They are not controlled by the en echelon fault belts whereas the NNW faults are restricted to the areas bounded by these belts. The NW faults link the E-W en echelon fault belts and form a characteristic zigzag pattern in the study area. Also, NW faults of the northern part of the Suez rift are joined to E-W faults of the Cairo-Suez District forming the same zigzag pattern. In this way, some of the displacement on the NW faults of the rift is transferred into the plate interior outside the rift. The model proposed for the structural deformation of the Cairo-Suez District indicates that some of the NW faults of the Suez rift propagated into the Cairo-Suez District at the early rifting stage. They acquired a zigzag geometry as they got connected to segments of E-W deep-seated faults of the District. The linked segments of the latter faults were rejuvenated by diagonal-slip movement with a subordinate right-lateral strike-slip component. The latter led to the development of en echelon fault belts in the overlying sedimentary section. Intrablock extension in the areas bounded by the E-W deep-seated faults led to the formation of the NNW faults.