GNGTS 2015 - Atti del 34° Convegno Nazionale

106 GNGTS 2015 S essione 1.2 channel related patch drifts, to migrating sediment waves and internal erosional discontinuities that are attributable to the effects of sea bottom currents. Along a seismic profile close to the shoreline, some peculiar geometries show a Plio- Quaternary sequence fractured in few blocks rotated over the MES. The inclined horizons seem to be not due to sea bottom currents, but probably to a local tectonic event. We are analyzing it using the Move software through a flattening of the strata and applying retro-deformation techniques. This approach allows the reconstruction of the original setting of the layers and to evaluate the possible correlation with local tectonics produced by a close magmatic event. In the uppermost sediments some profiles evidence a prograding sequence that is locally evidenced with an enlargement of more than 10 km toward the basin of the continental shelf. Conclusion. On the west Sardinian continental margin some characteristic geometries have been observed into the Plio-Quaternary sequence. Some multiple reflectors affected the seismic profiles caused by the shallow sea bottom in the continental shelf. These multiples were representing a noise partially covering the PQ primary reflectors. For this reason, a re-processing of the seismic data was applied. The de-multiplex processing, based on an f-k filtering, gave an improvement of the seismic signals and a better imaging of the structural features. The interpretation of the data have highlighted a clear base of the PQ sequence, represented by the MES or, more locally, by the top of the Gessoso-Solfifera Formation. A Lower Pliocene semi-transparent sequence has been recognized in the upper slope and in the shallow platform; it is characterized by a change to a more reflecting seismic facies that has been ascribed to a different sedimentary supply. The overlaying sediments (Upper Pliocene-Quaternary) show a more reflecting facies, often joined to a strong effect of the sea bottom currents. Finally, a prograding sequence is locally present in the northern sector of the studied area, largely developed toward the basin. The Plio-Quaternary layers are often crossed by some volcanic buildings directly overlaying the MES: their position inside the sediments and the (onlapping or smearing or pinching-out) terminations of the same sediments on the volcanic bodies makes difficult the evaluation of the age of this magmatic activity, regionally ascribed to the Tyrrhenian opening. These buildings Fig. 3 – Interpreted seismic profile: the MES is clearly evidenced by erosional truncation (on the left) and by the high amplitude reflectors at the top of the Messinian sequence. The semi-transparent Lower Pliocene is covered by the Upper Pliocene/Quaternary sediments which show complex geometry probably due to the sea bottom currents effect. A main volcanic building crosses the PQ sequence and affects the sea bottom.