Extensional Attenuation of Foreland Thrust Belts in the Western Mediterranean

Extensional denudation in the western Mediterranean formed deep basins in the core of subduction-related orogenic arcs. It has contributed to the exhumation of metamorphic rocks in the hinterland of the Betics, Apennines, Rif and Tell. However, fewer cases have been described as extensional denudation affecting Foreland Thrust Belts (FTB). Here we describe the extensional collapse of FTBs around the western Mediterranean in response to mantle subduction dynamics in a setting of NW-SE convergence between Africa and Eurasia. The extension of FTBs has occurred at the edges of migrating subduction systems like the Gibraltar, Calabrian and Tunisian Tell-Atlas arcs when lithospheric tearing has propagated under the foreland region. Inboard of Subduction Transfer Edge Propagator (STEP) boundaries continental crust can undergo peeling of its mantle lithosphere driving extension, Si-K-rich magmatism and topographic uplift. This tectonic mechanism has been described as edge delamination in the Betics and Rif. We describe examples of extended FTB’s in the Betics, Rif and Tell and their relation to mantle driven tectonic mechanisms.