The role of pre-salt relief and detachment surfaces in thin-skinned tectonics: The Palmahim rapidly gliding corridor and the Dor rollover anticline, offshore Israel

Abstract The post-Messinian thin-skinned extensional belt along the Levant continental margin (offshore Israel in the Mediterranean Sea) is explained by basinward gliding of a sedimentary section above a downward-flowing salt layer. Such gliding systems are common above salt wedges, where the salt-lying section moves away from its landward stationary part. Here we study two ambiguous bathymetric “disturbances” that deviate from this well-explained process. To clarify their origin, we explore the role of two key elements controlling salt tectonics: (1) The dual behavior of salt, which mainly acts as an active motion driver carrying its overlying rocks with it (coupled motion), but sometimes serves as a passive lubricant allowing overlying rocks to slide above it (detached motion). (2) The pre-salt relief, which controls the shape and thickness of the salt infill, and in turn controls the deformation above it. Based on detailed seismic mapping and structural restoration, we show that the Palmahim disturbance is a rapidly gliding corridor covering an ancient salt-filled canyon. The relative motion between this corridor and its surroundings formed two strike-slip faults on both sides. We illustrate that the relatively low area/perimeter ratio of the Palmahim narrow and elongated structure increases its resistance to failure and thus delayed its formation by ~2 m.y. compared with the regional initiation of salt tectonics. Distinctly, the Dor disturbance is a rollover anticline developed over an amphitheater-like salt-filled bay. The higher area/perimeter ratio of the Dor structure increased its susceptibility to failure, which thus started immediately with the regional salt tectonics. Initially, the Dor structure formed by gliding over a flowing salt layer (salt as an active driver). However, since the salt wedge had withdrawn from under the Dor structure, the upper block continues sliding over a salt remnant detachment surface (salt as a mere lubricant).