EVOLUTION OF THE ITALIAN LITHOSPHERE FROM S RECEIVER FUNCTIONS

Mediterranean tectonics has been characterized by an irregular, complex temporal evolution with episodic rollback and retreat of the subducted plate followed by period of slow trench-migration. To provide insight into the evolution of the entire peninsular Italy and south to the Calabrian arc, we image the characteristics and lithospheric structure of the entire convergent margin using teleseismic S-to-P converted phases. The lithosphere of the forelands (Apulian and Hyblean) at each cusp of the Calabrian arc are continental in nature, buoyant compared to the subducting oceanic lithosphere. They have previously been interpreted as mostly undeformed carbonate platforms, yet we image different thickness and morphology, which can be understood in terms of subduction dynamics. Our receiver function images show evidence of lithospheric erosion and thinning of these forelands closest to Mt. Etna and Mt. Vulture, two volcanoes which have been associated with asthenospheric upwelling and mantle flow around of the sides the slab. We suggest that as the continental lithosphere resists being subducted it is being thermo-mechanically modified by toroidal flow around the edges of the subducting oceanic lithosphere of the Calabrian arc. In contrast our receiver function images along the Northern Tyrrhenian Sea it appears that the lithosphere is thinned to approximately 60-km thick, where the Eurasia plate has been stretched by the retreat of the subduction zone eastwards towards the Adriatic Sea. We also find evidence for an extremely complex lithospheric and upper mantle structure along parts of the peninsula, where two different negative S-velocity jumps are present at approximately 90 and 160 km depth, which we attribute to stacked continental and oceanic lithosphere in regions where active subduction is still occurring.