Stratigraphy and structural context of the Neogene basins in the Termini Imerese area (NW Sicily)

This paper illustrates the results of a stratigraphical study carried out on the upper-Miocene deposits, outcropping in the north-western Sicily between Palermo and the Madonie Mountains. The stratigraphy and facies of the upper Tortonian-early Messinian siliciclastic deposits (Terravecchia Fm.) show a different evolution between the south-eastern and the south-western sectors of the examined area. In the Ciminna-Pizzo Bosco zone (south-western sector), the sediments of the Terravecchia Fm. indicate the infilling of structural depressions by a fining-upward deltaic succession. The paleocurrents data indicate flow towards the south. In the western side of Ciminna-Pizzo Bosco zone, two thick evaporitic successions are exposed, the lower one being strongly folded; the upper is subhorizontal, thus postdating a syn-depositional tectonics affecting the Messinian deposits. In the Scillato zone (south-eastern sector) the upper Miocene terrigenous sediments, consist of an alluvial fan evolving to shallow water marine environments, arranged into three distinct depositional systems, northward prograding and lapping down the substratum. The paleocurrents data indicate flow towards the north. In this sector the evaporitic deposits are poorly developed and the whole succession is undisturbed. These features indicate that the two basins evolved within different structural contexts. The Ciminna-Pizzo Bosco basin originated in the footwall of active thrusts, while the Scillato basin developed in a northern sector, controlled by extensional faults affecting the hangingwall of the thrusts. The present-day position of the Scillato basin, with respect to the Ciminna-Pizzo Bosco basin, is probably the result of a dextral offset along a transcurrent faults oriented N120 degrees E, connected to the recent evolution of the southern Tyrrhenian margin.