Structural framework and crustal characteristics of the Sardinia Channel Alpine transect in the central Mediterranean

Abstract

The submerged area located between the Sardinia Channel and the western Sicily offshore has been investigated based on deep crustal and conventional seismic lines with the aim of illustrating the relationships between the crust and its overlying crystalline and sedimentary thrust wedge. Analyses of seismic attributes and reflector pattern, supported by dredge hauls, also provided data in areas where stratigraphic and lithologic control is absent. Crustal geometries, tectonic processes and timing of the deformation are discussed here. North of the Elimi chain (central Sardinia Channel) the reflecting body consists of superposed tectonic wedges of crystalline rocks and their Meso-Cenozoic carbonatic and terrigenous cover (Sardinian and Kabilian–Calabrian units). The Kabilian–Calabrian units overthrust the Maghrebian–Apenninic units along the Drepano thrust front (Elimi chain), which is traceable on-land in eastern Sicily (Nebrodi–Peloritani Mountains). This lineament roots on the crustal–mantle discontinuity, where the local superposition of two different crusts occurs. The thrust front of the crystalline Kabilian–Calabrian units marks the boundary between thick-skinned and thin-skinned tectonics in the chain. The Apenninic segment of the chain develops between the Elimi sector and the Sciacca offshore (south-west Sicily). The crust is not as thick as expected in Alpine chain areas, suggesting pre-orogenic thinning of the African continental crust. The accretionary wedge is a southeast-vergent embricate fan consisting of four groups of thrust units formed by carbonate basinal and platform ramps with duplex geometries. The Mesozoic carbonate units are detached from the crystalline basement not involved in the deformation. The Tertiary terrigenous rocks are their roof thrust. The Upper Miocene clastic–terrigenous successions, sealing most of the structures, appear, in turn, detached and piled up. The intramountain Plio-Pleistocene basins display tectonic features that point out the area underwent both extensional and contractional tectonics.