The Alps in the Cretaceous: a doubly vergent pre-collisional orogen

Terra Nova, 24, 351356, 2012 Abstract Current palaeotectonic models see the Alps chiefly as a collisional orogen, with the Southalpine retrobelt developed only as a post-collisional feature. New structural and geochronological data show, instead, that the continental margin of Africa-Adria was being structured as a doubly vergent orogen during subduction of Alpine Tethys in the Cretaceous, tens of million years before collision with Europe. Subduction is envisaged here to have nucleated in the latest Albian/Cenomanian within the attenuated Adriatic margin. Most continental slivers exhumed as eclogites in the axial part of the Cretaceous orogen contain gabbros and relics of HT/LP metamorphic rocks, indicating inheritance from Permian to Jurassic rifting. Cretaceous shortening in the Southalpine retrobelt is indicated by several lines of evidence, including orogen-derived turbidites and syn-sedimentary compressional activity since the Cenomanian, Upper Cretaceous pseudotachylytes dating major S/SE-verging thick-skinned thrusts, and widespread fold-and-thrust deformation cut by Eocene plutons and dikes.