The West Sardinian offshore represents the east passive continental margin of the Ligure-Provencal oceanic basin. Since the Upper Oligocene the westward subduction of the Tethyan ocean below the Europe plate originated the opening of the Ligure-Provencal-Balearic back-arc basin. It was related to the separation from Europe plate and the anticlockwise rotation of the Corso-Sardinian block time. The rift sequence fills the graben and onlaps the north-sud horst of the basement (fig. 1.1A). After the end of the drift phase, during the MSC strongly affected the West Sardinian margin originating the erosional truncation (MES) on the slope and the evaporate deposition (Messinian trilogy of Rehault et al., 1984) on the deep basin (fig. 1.2). As in the main Mediterranean Sea, in the studied area the Lower Pliocene Trubi marls represents the quick drop of the sea level. The overlaying Upper Pliocene-Quaternary sequence is thick on the deep basin, while on the slope the sea bottom currents take a main role with erosion and reduced deposition on some limited throughs. Seismic facies of MSC unconformities and units are described.