GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 3.1 55 Fig. 3 – A) Comparison among vertical resolutions of WS, WMR, CROP seismic data and seismostratigraphy of the eastern Sardo-Provençal basin. B) Seismostratigraphy of the Western Sardinian Margin. C) Isochron map of the Plio- Quaternary sequence. out at 4 s TWT depth. Vertical load by the sedimentary overburden and seawater column produced a great amount of diapirs in the deep basin. In the upper slope LU, MU, UU are no more present and the lower unit (Lower Pliocene) of the PQ sequence directly overlays the pre-MSC sequences clearly depicted by the MES angular unconformity (Fig. 3B). The Plio-Quaternary isochron map (Fig. 3C) shows a time-thickness that increases toward the north-western basin, where locally it reaches the maximum value of 1.7 s TWT (in correspondence of increased accommodation space for the presence of weld). The Plio- Quaternary sediment supply has been much higher in the Gulf of Lion than that in the eastern part (Aslanian et al. , 2012; Geletti et al. , 2014). In this way, at the end of the Messinian salinity crisis event, the depo-centre of the study area moved in the eastern sector of the north-western Mediterranean deep basin. Conclusion. This work analysed the Messinian to recent geological evolution of the eastern sector of the Sardo-Provençal basin. The reprocessing of a selected part of the seismic profiles has been very useful to improve the imaging of the deep reflections below the salt layer. The depth migration is particularly useful as it reduces the pull up velocity effects when salt layers are present. Several velocity analyses were conducted on CMP gathers and related semblance panels (in time domain). On the basis of different trial methods however, all exhibit strong lateral velocity variations, due to the dense presence of salt diapirs in the investigated area.