ARCHITECTURE AND EVOLUTION OF THE ALPINE-MEDITERRANEAN COLLISION ZONE

The Alps exhibit a subduction polarity opposite to most Mediterranean orogens. They exceptionally well preserve the crustal and lithosphere-scale architecture due to “hard” collision during Cretaceous to Cenozoic Adria-Europe plate convergence (Schmid et al. 2006; Handy et al 2010). The Dinarides-Hellenides further to the east exhibit a subduction polarity with Adria occupying a lower plate position. The Dinaridic-Hellenidic orogen started to form by obduction of very young oceanic lithosphere derived from the northern branch of Neotethys onto Adria in latest Jurassic times, i.e. at the same time the Alpine Tethys started to open (Schmid et al. 2008). Massive roll back in the Aegean, starting in Late Eocene times, did not alter the polarity of subduction but led to extension in the upper plate at a rate that approximately equals rate of subduction.

The transition from subduction driven by overall Africa-Europe plate convergence (“hard collision”) to subduction induced by the negative buoyancy of the subducting slab (“soft collision”) led to a more dramatic reorganization within the Western Mediterranean realm starting in latest Eocene times. This reorganization led to the opening of large new oceanic domains in the Western Mediterranean while old branches of Alpine Tethys totally disappeared by subduction or obduction, and additionally, to a reversal of subduction polarity affecting the SW intra-oceanic prolongation of the former Alps (Handy et al 2010). Rollback subduction of the Ligurian part of Alpine Tethys attached to the Adria microplate involved the formation of the eastward retreating Calabrian arc since about 35 Ma ago, linked to orogeny in the Apennines and Northern Africa. The westward retreating Gibraltar arc represents a second arc-trench system. These reorganizations were driven primarily by the pull of the gravitationally unstable, retreating oceanic parts of the Adriatic and African slabs during slow convergence of Africa and Europe.

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Schmid, S.M., Fügenschuh, B., Kissling, E. and Schuster, R., 2004. Eclogae geologicae Helvetiae 97: 93-117.

Schmid, S.M., Bernoulli, D., Fügenschuh, B., Matenco, L., Schefer, S., Schuster, R., Tischler, M. & Ustaszewski, K., 2008. Swiss Journal of Geosciences, 101(1): 139-183.