Structures associated with extensional tectonics in the Suez rift

Abstract

Summary The opening of the Suez rift, which was initiated at the beginning of the Miocene (23 Ma), was the result of a regional extensional stress more or less perpendicular to the rift axis. A detailed study of selected areas within the onshore part of the rift (Abu Durba, Gebel Ekma and Wadi Dib) shows that the fault geometries visible in the Precambrian basement and the overlying sedimentary rocks are distinct; brittle deformation in one, ductile deformation in the other. In the basement (metamorphic and granitic rocks), faults display a rectilinear pattern. Two sets of faults are predominant; (i) N140-150E faults, parallel to the Gulf trend, with pure dip-slip displacement, (ii) cross-faults (transfer faults) trending N00 to N30E with strike-slip component. These faults delineate diamond-shaped tilted blocks. In the overlying sedimentary rocks (Cretaceous-Eocene sands, shales and limestones) faults are spoon-shaped. Spoon faults are generally superimposed over concave wedges of the basement blocks but are decoupled from basement fault sets. The decoupling is accommodated by ductile deformation and detachment in the Cretaceous marks.