Fold-related faults in the Syrian Arc belt of northern Egypt

Abstract

Late Cretaceous–Early Tertiary Syrian Arc folds in northern Egypt include both inversion and non-inversion folds. These folds are well exposed in northern Sinai and the northern Eastern Desert but exist in the subsurface in the northern Western Desert. In northern Sinai, the Maghara, Yelleg, and Halal inversion folds are 45–50 km long. Similar size inversion folds with opposite vergence exist in the subsurface in the northern Western Desert and include the Kattaniya, Mubarak, Alamein-Razzak, and Matruh Basin folds. Smaller non-inversion compressional folds include the Falig and Meneidret El Etheili folds in northern Sinai as well as the Abu Gharadig Anticline in the subsurface in the northern Western Desert; among others.Detailed surface and subsurface structural mapping made use of the excellent exposures and good 2D and 3D seismic data and led to the identification of the fault patterns of the inversion and non-inversion Syrian Arc folds. Inversion folds have fault patterns that differ from the backlimb to the forelimb. The backlimbs are pervasively dissected by long NW-SE oriented normal faults that were formed by the regional stress field. On the contrary, the forelimbs of inversion folds as well as the two limbs of non-inversion folds are affected by the local stress in the folded areas and are dissected by three shorter fault sets; a set of hinge-transverse normal faults and two conjugate sets of hinge-oblique faults that have oblique-slip. The hinge-oblique faults dominate the steeper limbs of asymmetric non-inversion folds.