Rejuvenation of the Tethyan passive continental margin of northern Sinai: deformation style and age (Gebel Yelleq area)

Abstract

Detailed field mapping and structural analysis of the northeastern and southeastern parts of Gebel Yelleq (the largest fold among the northern Sinai folds) indicate the presence of two ENE-oriented dextral wrench zones. The northern (Meneidret El Etheili) wrench zone is represented by right-stepped, en échelon doubly plunging folds whereas throughgoing wrench faults characterize the southern (Minsherah) wrench zone. The steep (southeastern) flank of Gebel Yelleq asymmetric fold makes an acute angle with the wrench zones and is orthogonal to the NW-SE-directed shortening direction indicated by mesostructures. Similar structural relations are evident in the other major folds of northern Sinai, Gebels El Maghara and Halal. A structural model is proposed for the deformation of northern Sinai. Late Cretaceous-Tertiary rejuvenation of the early Mesozoic passive continental margin of the Neotethys proceeded via right-lateral wrenching in northern Sinai and is related to the oblique convergence between Africa-Arabia and Eurasia during the closure of the Neotethys. As a result, wrench zones developed above the early rift faults, e.g., Meneidret El Etheili and Minsherah wrench zones. Also, NW-SE-directed shortening related to and parallel to the convergence of Africa-Arabia and Eurasia deformed the blocks lying between the wrench zones through the development of NE-SW-oriented thrust faults, at acute angles to the wrench zones. These thrusts ruptured the Precambrian basement and propagated upward through the overlying sedimentary cover as listric thrust faults forming large fault-propagation folds in Gebels Yelleq, El Maghara and Halal. These thrusts underlie the steep southeastern flanks of these folds and are exposed in Gebels El Maghara and Hamayir. The depth to detachment of these thrusts progressively increases southward to a value, underneath the Gebel Yelleq area, close to the brittle-ductile transition of the crust. The deformation reached its zenith in the early late Senonian and probably continued into the Early Miocene. The northern Sinai fold belt characterizes an unstable crustal block separated from a tectonically stable crustal block to the south, in central and southern Sinai, by a belt of ENE-oriented closely spaced faults forming what is called the central Sinai “hinge belt”.