Timing and magnitude of rotations in the frontal thrust systems of southwestern Sicily

We report new paleomagnetic and anisotropy of magnetic susceptibility (AMS) results from upper Tortonian to middle Pleistocene sediments which were de posited upon and adjacent to active thrust structures in southwestern Sicil y. The data show that the Plio-Pleistocene sediments from the Belice and Me nfi basins (covering the Saccense shelf limestones) underwent any internal shortening after the early Pleistocene (Santernian), as well as any net rot ation. Sediments around this area (which overlie basinal Meso-Cenozoic succ essions) record systematic rotations: one upper Tortonian site to the west is similar to 30 degrees counterclockwise rotated, while to the east, lower Pliocene to middle lower Pleistocene sites within the Gela Nappe domain sh ow 25 degrees to 56 degrees clockwise (CW) rotations. These data show that the ductile basinal sediments were bent and rotated around the rigid Saccen se carbonates during the thin-skinned southward propagation of the orogenic front. We document here that the coastal sediments from the southwestern G ela Nappe underwent both a post middle early Pleistocene similar to 30 degr ees CW rotation and a post middle Pleistocene E-W to ESE-WNW flattening (re vealed by AMS). Our data then constrain to the late Pleistocene-Holocene th e age of the last shortening episode occurring in the southwestern Gela Nap pe front. Pleistocene rotations of similar amount also characterize the Sic anian domain, implying that it was incorporated in the Gela Nappe wedge dur ing the recentmost episodes of deformation. This evidence allows us to bett er understand the very large (up to 114 degrees) post Mesozoic rotations re ported by Channell et al. [1980, 1990] for the Sicanian limestones, as rela ted to both Miocene (or older?) deformational episodes and the Plio-Pleisto cene evolution of the Gela Nappe.