Facies and geometry of an Upper Jurassic-Lower Cretaceous carbonate rimmed-shelf system from Northwestern Sicily

Upper Jurassic-Lower Cretaceous carbonate shallow-water successions, several hundreds of meters thick, outcropping in the Palermo Mountains (NW Sicily, Italy), are analyzed in their sedimentological features for environmental reconstructions. In the Palermo Mts., the northernmost thrust system of the western Sicily fold and thrust belt, tectonic bodies, consisting of Upper Triassic-to-Eocene shallow-water carbonates (Panormide carbonate platform), outcrop. Detailed facies and microfacies analyses, stratigraphic measurements and physical stratigraphy studies of the Tithonian-Neocomian carbonates point out the occurrence of several lithofacies, from tidal flat to reef environments. Due to the strong deformation of the Palermo Mts. belt, the study successions outcrop, frequently, in tectonically separated and isolated bodies, making difficult to recognize their mutual facies relationships. The grouped facies associations, pertain to: a) peritidal platform, consisting of regular alternation of grey wackestone with algae and molluscs, packstone with cavities filled by sparry calcite (birds eyes), stromatolitic laminae, loferitic breccias and oolitic grainstone (tempestites); b) shelf margin, consisting of oolitic and bioclastic packstone-grainstone, alternated to bioclastic wackestone with large mollusc shells, mostly gastropods, algae and benthic foraminifers and bioclastic muddy sands; these deposits are believed to point out the leeward side of a sand bar, passing to the protected shelf lagoon. In other sites, the oolitic lithofacies alternated to bioclastic packstone and fine breccias with reef-derived elements are interpreted as the windward side of the oolite shoal, passing to a high energy zone gradually merging in to reef complex; c) reef margin, consisting of boundstone with corals and hydrozoans (Ellipsactinia sp.), intra-reef breccias and bioclastic grainstone, with rim cements and cavities filled by silt; d) upper slope-fore reef environment, consisting of bioclastic packstone-to-grainstone and lithoclastic rudstone with reef-derived elements. These lithofacies are organized in shallowing-upward cycle sequences. The reconstruction of the lateral relationships among the several facies associations points out that the studied deposits were formed in a carbonate rimmed-shelf depositional system, characterized by aggradational and progradational stratigraphic architecture, along the Sicilian sector of the southern Tethyan margin.