The Ussana “Fm”: insight about the Sardinian rift from a syn-tectonic unit evolving through space and time

The meaning and the space-and-time variable depositional features of the Ussana “Fm” and of the related coeval units, base of the Late Oligocene - Miocene succession of the Sardinian rift, are discussed. These features, and the presence/absence itself of the Ussana Fm, are related to tectonic and paleomorphologic characters of the Sardinian rift shoulders and their evolution. The features of the Ussana Fm evidence the changing characteristics of the Sardinian rift up to the southern Corsica area. Giving the extremely variable characters of the stratigraphic sections of the Ussana Fm from S to N and also at short distance, a possible lithostratigrahic upgrade of the unit to litostratigrpahic group is proposed.