Evolution of Strike-Slip Duplexes and Wrench-Related Folding in the Central Part of Al Jabal Al Akhdar, NE Libya

The deformation in the central part of Al Jabal Al Akhdar, NE Libya, is dominated by E-W right-lateral strike-slip fault zones that form a conjugate system with the N-S left-lateral strike-slip faulting. The dextral wrench-dominated transpression is responsible for the formation of strike-slip duplexes, en echelon folds, and thrusts that deform the Cretaceous-Eocene sedimentary sequences. The strike-slip duplex is formed by the progressive linkage of horsetail-like structures at the western tip of the Al Bayda strike-slip fault that joined splays coming from other dextral strike-slip faults. The master linear fault branches into second-order dextral or sinistral faults that regroup into a linear single fault. Faults started from arrays of en echelon extensional/extensional-shear fractures that then coalesced into throughgoing strike-slip faults. Shortening was accompanied by significant N-S-striking left-lateral strike-slip displacements, with the development of NE- to ESE- and SW-plunging major folds, N-directed thrusts, and NW-striking normal faults. These major folds are C-system wrench-related folding, of the sort that usually play an important role in oil and gas accumulation. Three major compressional events occurred in the Santonian, Campanian-Maastrichtian, and early Late Eocene, alternating with extensional periods in the Oligocene, Early–Middle Miocene, and Pliocene. These events developed the folding of the Syrian Arc and strike-slip faulting along the NE African–northern Arabian margin, including Al Jabal Al Akhdar.