VERY-HIGH RESOLUTION ANALYSIS OF A TRANSGRESSIVE DEPOSIT IN THE NORTHERN ADRIATIC SEA (ITALY)

The Adriatic Sea is characterized in the northern and central shelf by different generation of isolated transgressive bodiesformed and drowned in-place during the last relative sea-level rise. The continental shelf is characterized by a low gradient and, within thetransgressive deposits the episodic variations in sea level and sediment supply caused the formation of backstepping parasequences. Thetransgressive bodies have been studied in detail because they have considerable amount of sorted sand exploitable for beach nourishment.A transgressive deposit, located south of the Po Delta, offshore Ravenna at depth of 34-35 m, has been investigated with a totalcoverage of very-high resolution (VHR) seismic profiles and high number of cores in order to understand the stratigraphic evolution duringthe late Quaternary sea-level rise. The transgressive body is composed of four seismic units separated by high-amplitude and high continuityreflectors, corresponding to peat and organic-rich layers indicating different depositional phases. The core analysis confirmed the presenceof different units showing sediment variation from clay with peat-layer at the base to fine-grained sand at the top of the deposit. Furthermore,the core analysis gave information about the thickness of the deposit. The thickness of the transgressive body is from 3 to 5 mand each unit varies from 1 to 2 m. In particular, the sand portion reached a maximum thickness of 1.5 meters. The seismic analysis andthe digital elevation model constructed for key surfaces highlighted the channel system direction was towards ENE during Last GlacialMaximum and during sedimentation of Unit 1 and 2, while it shifted toward ESE during the formation of Unit 3. Moreover, to constrain thechronology of the sedimentary evolution, some peat and organic-rich samples, have been dated with 14C method. These organic horizonsare evident seismic reflectors and correspond to key surfaces. They are characterized by brackish lagoon facies and could be a proxyindicator for the relative paleo-sea level. Along with the previous data, they indicated that the sedimentation of the studied transgressivebody occurred around 10,000 cal. a BP.