GNGTS 2013 - Atti del 32° Convegno Nazionale

sponsored by CNR, Ente Nazionale Energia Elettrica (ENEL) and Ente Nazionale Idrocarburi (ENI); high resolution seismic profiles of the WS10 Project acquired and processed in 2010 by the R/V OGS Explora in the western Sardinian offshore. Geological setting. Seismic profiles of the Mediterranean basins have been analysed by many Authors (CIESM, 2008; Lofi et al. , 2012 with cited references) to reconstruct the different seismic signature of the Messinian Units. The “Messinian trilogy” recognized in the Balearic abyssal plain (Rehault et al. , 1984), has been expanded on with the interpretation of the different seismic facies that form the Lower evaporite Unit (LU), the salt Mobile Unit (MU) and the Upper evaporite mainly gypsiferous Unit (UU). On the lower continental slope of the West Sardinia margin, which represents the eastern passive margin of the Balearic Basin, a thinning salt layer overlayed by the Upper Unit, turns into the Messinian Erosional Surface (MES): it is generally characterized by a strong reflector which truncates the top lapping pre- Messinian reflectors. The Ionian oceanic crust underthrusts below the Calabrian and Hellenic Arcs forming active subducting slabs. In the deep basin the Messinian event is commonly evidenced by gypsum and salt layer that was piled up by compressive tectonics for a total thickness of some hundred meters (Finetti, 1982). The Ionian Basin represents, with the Levantine Basin in the Eastern Mediterranean Sea, the remnant of the Permo-Triassic Neo-Tethys (Finetti, 2005; Stampfli, 2005); the basin is characterized by a thick sedimentary package overlying the oceanic crust where the Messinian salt is often affected by plastic deformation. The Messinian trilogy seems to be absent and only MU, with some internal reflectors, has been recognized (Lofi et al. , 2012), bounded by two erosional surfaces on the top and on the bottom. Fig. 2 - A:seismic profile WS 10-07 located in map where the continental slope and basin domains are respectively highlighted in frames B and C. In B the stratified Plio Quaternary sequence covers the Upper Units (UU) deformed by salt tectonics where the Mobile Unit (MU) is evidenced with transparent facies. The underlying Lower Unit (LU) is weakly reflecting, due to the high absorption by the diapir structures. In C the Messinian Erosional Surface (MES) on the slope clearly truncates the pre-Messinian horizons. 57 GNGTS 2013 S essione 3.1