Sedimentology of a drowned carbonate platform from the Sciacca area (southwestern Sicily): Insights into the Jurassic palaeogeography of Western Tethys

Abstract

A sedimentological-stratigraphic study of the Mesozoic carbonates exposed in two inactive quarries in southwestern Sicily has provided new insights into the palaeogeographic evolution of the southern sector of the Western Tethys margin during the Jurassic.

The Lower–Upper Jurassic succession consists of shallow-water peritidal carbonates, intersected by neptunian dykes and sills, which transition upwards into condensed pelagic limestone. Microfacies analysis of the shallow-water peritidal carbonates has led to their reassignment to the Hettangian–Pliensbachian (p.p.), previously attributed to the Late Triassic. Furthermore, variations in biodiversity within these stratigraphic horizons reflect the survival and recovery interval following the end-Triassic mass extinction event.

The abrupt transition to condensed pelagic limestone indicates the drowning of the carbonate platform. Lateral facies variations observed within the condensed pelagic limestone suggest different sedimentological processes, influenced by a complex system of structural highs and basins related to the Pangea continental rift. The presence of distinctive micro- and macrofacies, such as micritic oolites and FeMn hardgrounds, indicates a varied palaeotopographic setting for each section, where sedimentation is further controlled by bottom-current activity and low sedimentation rates.