Transpressional inversion and fold superimposition in the southern Eastern Desert of Egypt, East African Orogenic Belt
Mohamed A. Abd El‐Wahed, Mohamed Attia
Abstract
Transpressional deformation had a key role during the Neoproterozoic development of the East African Orogenic Belt and the Arabian–Nubian Shield. This study examined the folding structures in the Kharit Shear Zone (KSZ) in the southern Eastern Desert of Egypt. We investigated the relationship between the development of large-scale folds and the mechanism of transpressional inversion within the KSZ. Structural analysis showed the occurrence of extensive folds formed through three generations of folding and their associated fabrics. The F1 folds developed during an early phase of north–south shortening, whereas the F2 folds, distinguished by their overturned and doubly plunging forms, are associated with dextral transpressional deformation along the KSZ. The subsequent F3 folds, by contrast, are indicative of sinistral transpressional shearing, implying a transpressional inversion that evolved from pure shear to increasingly intricate patterns of fold interference throughout the shear zone. Regionally, the interference pattern changes from west to east, transitioning from lobate-cuspate shapes to mushroom shapes and then to crescent shapes. The refolding of map-scale NE-trending folds by NW- and WNW-trending folds led to the formation of this fold interference structure. Transpressional shear systems rework and reactivate rocks along opposing kinematic planes. This shear sense reversal emerged from the oblique convergence of East and West Gondwana, coinciding with the activity of the Najd fault system between 620 and 540 Ma.