Plio-Pleistocene wrench tectonics in the Western Sicily Chain

Abstract

Western Sicily represents a fragment of the Apenninic-Maghrebian Chain, largely built during the Miocene and formed by a set of tectonic units with southern vergence of folds and ramp-flat style of thrust surfaces. The thrust tectonics-related structures are displaced by a high-angle fault system, which bounds the main Mesozoic “carbonatic massifs” and generally interpreted as a neotectonic dip-slip extensional tectonics-related faults. The present paper, with the support of mesostructural analysis, presents an important Plio-Pleistocene strike-slip tectonics, represented by high-angle net- and strike-slip fault system. Different scale flower structures and associated fold systems, which cut the Miocene tectonic units, characterise the areas along the main transcurrent fault zones. Strike-slip neotectonics is mostly represented by right-lateral NW-SE/W-E and left-lateral N-S/NE-SW transcurrent faults, which may represent a W-E trending deep-seated Riedel system connected to the Tyrrhenian spreading. The NW-SE first order synthetic structures appear to control the opening of several rhomboidal tectonic depressions located in north-western Sicily and its offshore, and are counteracted by W-E trending transpressional structures located in the central Sicily mainland. An attempt at semi-quantitative restoration show’s the neotectonic evolution of north-western Sicily during the Pliocene and Pleistocene, characterised by the progressive activation towards the east of en-echelon strike-slip fault strand, in an overall horsetail splay geometry, which produced releasing bends in off-shore and restraining bends in the mainland.