Abstract

Western Sicily is part of the Sicilian chain, a sector of the SE-verging Alpine orogenic belt in the central Mediterranean. Interpretation of seismic reflection profiles, boreholes and recent inland geological data, have enabled us to assess the deep structural grain. A wedge of flat-lying Mesozoic–Miocene carbonate and terrigenous rocks (pre-Panormide nappes) is superimposed on NW-trending, 7–8 km thick, Mesozoic–Paleogene carbonate thrust ramps (Trapanese units), arranged in two structural levels extending from the Tyrrhenian coast to western offshore Sicily. Upper Miocene to Pleistocene terrigenous strata, often deformed, fill syntectonic basins above the thrust pile. The main tectonic transport of the thrust pile, developing from Early Miocene to Early–Middle Pleistocene times, was towards the east and southeast.

Initial stacking and deformation of the pre-Panormide allochthon is bracketed between Early and Late Miocene. The Late Miocene–Early Pleistocene underthrusting of the Trapanese–Saccense units, that acted through more recent deep-seated thrusts in the carbonate platform layer, induced late stage refolding and further shortening in the early emplaced pre-Panormide nappe. Previously formed structures appear to have been dissected or reactivated by a right oblique transpression during the Late Pliocene–Pleistocene. The geometry of the carbonate bodies opens new potential perspectives on the existence of structural traps, but the uncertainties of source rock occurrence remain.

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