Evidence for Mantle Exhumation Along the Arabian Margin in the Zagros (Kermanshah Area, Iran)

Abstract

The Kermanshah Crush Zone (Zagros, Iran) comprises elements from the Tethys Ocean and the former ocean–continent transition. Serpentinites and gabbros exposed in this area were formerly interpreted as originated fromTethys ocean and other residual Tethys oceanic domains all situated northeast of the Bisotoun platform. However, the structural relationships between these ultramafic units remained unclear. New field work in the Kermanshah–Harsin area led to the description of detachment faults over serpentinised mantle. “Mid-Cretaceous” carbonate “extensional allochthons” (prerift) and pelagic sediments (syn- to post-rift) dated from the Liassic are exposed above these detachments. Such an age mismatch can be explained by a polyphased mantle exhumation in a narrow basin along the Arabian margin with the assumption that no radiolarite nappe has been thrusted over the Bisotoun. Another detachment has been identified further to the NE on Eocene gabbro. So far, this one is considered as an intra-oceanic detachment from the residual Tethys. A first evolution model is proposed from early Jurassic to late Cretaceous obduction along with how this interpretation may be improved by future field work.