GNGTS 2014 - Atti del 33° Convegno Nazionale

intra UU salt layer in the deep basin and a main erosional surface, already locally recognized in some West-Mediterranean margins and called IES (Intermediate Erosional Surface) by Lofi et al. (2011), on the lower slope. Geletti et al. (2014) hypothesized that these two features are coeval and could be originated by a sea level drop during the UU deposition. This represents a still open question about the evidences of more Messinian sea levels drops which produced not only the main salt units of the Messinian trilogy, but eventually also further internal intercalations. In theAlgero-Balearic abyssal plain (Sabat et al. , 1995; Camerlenghi et al. , 2009, 2014�� ��� ), and in the eastern Sardo-Provençal basin (Geletti et al. , 2014; Del Ben et al. , 2014) the Messinian evaporite sequences evidence salt domes and diapirs with associated normal faults; the domes and diapirs have been originated by movement of the Messinian salt of the MU and, locally, also by the salt layer inner the UU (Geletti et al. , 2014). The halokinetic processes started during the Late Messinian, as testified by some growth strata of the UU, and developed till recent, locally affecting the seabed. The Pliocene-Quaternary sediments showed internal unconformity related to the final emplacement of the diapirs, which are more recently active at the foot of the escarpments. Messinian evaporite sequence has been recently interpreted in a wide study of Maillard and Mauffret (2013), along seismic profiles from the Ibiza channel to Alicante; they interpreted the Miocene/Pliocene boundary either as an erosional surface that cuts the underlying reflectors and/or dividing two different seismic facies, in that case associated to the Marginal Erosional Surface observed along the Mediterranean margins (MES, Lofi et al. , 2011). Sometimes the boundary is represented as the top of chaotic reflections interpreted as MSC-related deposits [Chaotic Unit, clastics and/or evaporites, by Lofi et al. (2011)]. Otherwise the evaporite are well recognizable thanks to high amplitude reflections. Salt-induced abyssal plain sediment deformation have been recently identified by Camerlenghi et al. (2009) below the EBE in the area south of Ibiza classifying four different kinds of deformational structures: 1) a belt of elongated abyssal plain seahills, 2) anastomosing knolls in the Menorca fan area, 3) abyssal knolls and seahills across the basin and 4) a mud volcano extruding sediments and fluids of likely pre-Messinian origin. Seismic datasets. The seismic datasets used in this work belong to two different research projects that involved the R/V OGS Explora to investigate the Messinian and post-Messinian sedimentary sequences. A general purpose to explore also the uncalibrated pre-Messinian sequence represents a very difficult goal, due to the high absorption of seismic energy by the evaporite layer that requires higher energization and lower frequency of the seismic source. For both the multichannel seismic datasets the used acquisition parameters allowed to improve the resolution of the pre-existing profiles in this region (MS and CROP seismic data) and obtain the better compromise between resolution and penetration of investigation. In 2010, the West Sardinia project (WS10) has been performed within the eastern sector of the Sardo – Provençal basin and on its passive margin (location in Fig. 1). 15 MCS profiles were acquired: seismic source made up of an array two GI-guns with a total volume of 16.3 litres, towed at 4 m depth, shot interval 25 m, 1.5 km length of digital streamer and 120 traces with spacing interval 12.5 m. Seismic processing has been performed using industrial software packages Focus, Geodepth by Paradigm and Promax by Halliburton; Academic grant of Petrel (Schlumberger) have been used (Geletti et al. , 2014). In 2012 a seismic dataset of 12 multichannel reflection profiles, sub-bottom profiler and multibeam bathymetry have been acquired within the Eurofleet project SALTFLU: Salt deformation and sub-salt fluid circulation in the Algero abyssal plain (location in Fig. 1). The used sources for seismic data were made up of two arrays of four GI-guns towed at 3 meters depth and shot interval of 25 meters, 3km length of digital streamer and 240 traces with spacing interval 12.5 meters. The seismic profiles presented in this work are post-stack migrated section (Camerlenghi et al. , 2014). 158 GNGTS 2014 S essione 1.2