Facies Architecture and Evolution of a Cretaceous, Tectonically-Controlled, Carbonate Slope from Western Sicily (Italy)

The stratigraphic architecture of a Cretaceous carbonate slope from north western Sicily (Italy) has been reconstructed on the basis of detailed field sections. The wire cut walls of a number of quarries that extract the Cretaceous limestones as ornamental stones allowed the mapping of the stratal architecture and lithologies at various scales. The vertical and lateral facies relationships in this about 1000 m thick depositional system account for a complex sedimentary dynamics along a carbonate platform escarpment that was strongly influenced by syn-sedimentary transtensional tectonics associated to magmatism. Although the original relationships with the carbonate platform were obscured by the Maghrebian orogeny, the source area of the clastic carbonates can be envisaged in the Panormide Platform, a paleogeographic unit Late Triassic to Eocene in age that crops out in northern Sicily. The most common facies along the Cretaceous slope are mass transport deposits (MTD) with large (decimetre to metre-scale) elements of rudist limestone in a matrix of skeletal rudstone. They alternate to finer grained gravity flow deposits. Thin intercalations of Scaglia-type calcilutites (background sediments) point to occasional interruptions of the gravity flows. The onset of the slope sedimentation occured in the Berriasian, as documented by the abrupt overlap of MTD with ellipsactinids/corals extraclasts on calpionellid wackestone. This event points to the conversion of a gentle ramp into a faulted escarpment that has favourded the collapse of the ellipsactinid-bearing extraclasts. Two subsequent episodes of dissection of the slope are indicated by pillow basalt intercalations. Based on the benthic communities in the overlapping sediments the lava emissions could be constrained to the Aptian and Albian. As recorded in many others carbonate platform-basin systems, the Cenomanian records a maximun downslope shedding of skeletal debris transported by turbidites and grain flows. A progressive decrease of the clastic supply along slope is recorded from Senonian onward as a consequence of the gradual drowning of the adjacent platform. However, the resedimentation pulses lasted at least up to the Maastrichtian thus indicating the perduration of a shallow water carbonate production in small isolated patches. The study provides new insights for the understanding of the sedimentary dynamics along Cretaceous escarpments from western Tethys controlled by crustal extensional deformations