Structural Pattern of Egypt and Its Interpretation

Abstract

Most of the structural elements of Egypt could be fitted into a pattern that appears to have been originated by compressive stresses that acted mainly from N. 10° W. and S. 10° E. During the Precambrian these stresses already were active and they produced shears which were expressed as right- and left-lateral strike-slip faults at the Gulfs of Suez and Aqaba, the Red Sea, and most of the Nile Valley in Egypt. These same stresses, after slightly shifting westward, produced the North Sinai folds. Theoretically, the original forces could have produced nearly east-west thrust faults. However, faults that trend in this direction (other than those associated with major folds) are either gravity or strike-slip faults. It is contended that the walls of the ancient thrus s were peneplaned before the deposition of younger sediments. Later displacements along the same faults were either downdip (gravity) or parallel with their strikes (strike-slip). Several uparching movements, of which the most important occurred during the Paleogene, caused stretching and consequent downfaulting of grabens mostly along the ancient lines of weakness produced by shearing. Differential vertical block movements of adjacent strips of the basement resulted in folding and faulting in the overlying sediments. Supratenuous folds have been formed whenever block movements were contemporaneous with sedimentation. The bearing on the occurrence of petroleum of the integrated structural pattern presented here is discussed.