GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 3.2 533 The used approach has allowed to obtain comparable information for all the margins of the Italian Peninsula without a strong influence of local and particular aspects (Aiello and Budillon, 2004). The last Late Quaternary sea level rise, having an excursion of 120 m and a maximum rate in the order of 10 m/1000 y has left an imprint on the morphologic and stratigraphic setting of many continental margins of the earth. The deposits related to this process are strongly different in several areas as a function of variable sedimentary supply, morphologic setting and oceanographic regimes. Through this approach the facies, the internal geometries and the thickness of the Quaternary deposits may be studied. These factors record the process of eustatic sea level rise in differential ways on several continental margins. The geologic interpretation of the seismic sections has been carried out according to the criteria of seismic stratigraphy. This has allowed to distinguish the main seismo-stratigraphic units occurring in the subsurface, separated by main reflectors, corresponding with main surfaces of conformity or unconformity. The interpretation of seismic sections has allowed to carry out a distinction between the acoustic basement, cropping out in wide sectors of the nearshore area, for an extension at the sea bottom resulting higher with respect to that one singled out by previous studies (Coppa et al. , 1988; Ferraro et al. , 1997) and the zones of accumulation of sediments. The geologic interpretation of Chirp profiles located in the Licosa morpho-structural high has evidenced the occurrence of the acoustic basement on Chirp lines (unit S), cropping out at the sea bottom nearshore and dipping seawards under the Quaternary deposits, forming the recent sedimentary cover. Unit S correlates with the Cilento Flysch Formation, widely cropping out in adjacent emerged sectors of the Cilento Promontory. The remnants of terraced surfaces located at different water depths, detected on seismic lines have evidenced the complex morpho- evolution of the acoustic basement during the Late Quaternary. The seismic data analysis has suggested that the acoustic basement was involved in several phases of erosion/emersion, development of terraces and successive transgression, as a consequence of both the Late Quaternary glacio-eustatic sea level fluctuations and of the Pleistocene tectonic uplift. The outcrops of the acoustic basement, related with the “Flysch del Cilento” Auct. , widely cropping out in the surrounding emerged sectors, are widely diffused in the bathymetric belt ranging between the –10 m and the –50 m of water depths (then in the inner shelf) and form terraced surfaces having a low gradient occurring in the inner shelf between the Solofrone river mouth and the Licosa Cape. Four orders of terraced surfaces have been recognized based on geologic interpretation of Chirp lines. The oldest ones are located at water depths ranging between 50 m and 43 m. They are genetically related with the terraced surfaces disposed at several water depths, ranging between 46 m and 44 m in the Palinuro Cape area (Antonioli et al. , 1997). The second order of terraced surfaces has been identified at water depths ranging between –18 m and –24 m in the Palinuro Cape area (Antonioli et al. , 1997). The third order of terraced surfaces has been recognized at water depths ranging between –10 m and –14 m and is related with similar surfaces disposed at water depths ranging between –12 m and –14 m in the Palinuro Cape area (Antonioli et al. , 1997). Finally, the terrace rims occurring at –8 m are coeval, if not older, than the last interglacial and are related with the last part of the isotopic stage 3. On the basis of high resolution reflection seismics it has not been possible to recognize the Eutyrrhenian palaeo-sea level mark or related deposits. The analysis of the seismic signal and the correlation with Sidescan Sonar sonograms recorded on the same navigation lines of Subbottom Chirp lines have evidenced the occurrence of widespread grasses of Posidonia oceanica and Cymodocea nodosa , particularly occurring in shallow sea bottoms up to –50 m of water depth. Proceeding seawards, the acoustic basement is downthrown by normal faults below the recent sedimentary cover, which is organized in three main seismo-stratigraphic units separated by unconformities.