Very-High Resolution Seismo-Acoustic and morphologic investigations of a Holocene transgressive system in the Northern Adriatic Shelf

The reconstruction of the various steps of the sea-level rise, in addition to the academic interest, can be useful in many application areas, such as the seek for exploitable sand bodies and the study of the evolution of a coastal environment under condition of sea transgression. In this work several seismo-acoustic profiles are analyzed, along with other geophysical data from a 45 km2 area of the northern Adriatic Sea; the majority of these data were collected during the CNR-ISMAR Bologna ASCI14 marine survey, onboard of the R/V Urania. Through the analysis of these profiles three detailed 3D paleo-surfaces were reconstructed, representing different moments during the sea-level rise. The combination of data inferred by paleo-morphologies and sedimentary structures allows to hypothesize the evolution of the study area approximately during the last 10 000 years: the depositional environment gradually shifts from an alluvial plain, characterized by meandering-pensile rivers, to a lagoon-brackish swamp, which was then drowned and covered by prodelta-offshore deposits. The area is characterized by the presence of a deep erosive scour, which has been interpreted as a tidal inlet on a stratigraphic and geomorphological basis. This information has interesting implications on the interpretation of the numerous similar erosive features of the northern Adriatic basin. The presence of the tidal inlet represents a clear indicator of the sea-level position and allows to estimate the age of the linked lagoon-brackish swamp deposits which, basing on the observed sea-level rise curve for the Adriatic Sea, is likely comprised between 9 800 and 9 850 years BP. The further comparison of this inferred age with a geophysical model for the sea-level rise in the northern Adriatic Sea allows to estimate a subsidence of 0.02 cm/year for the area, which is well-comparable to other data from published works. This work concludes with the presentation of some paleo and present analogous morphologies and stratigraphies, which may be compared to the study area in order to obtain some important information about their evolutionary history. The Adriatic area is characterized by a huge amount of geophysical data and cores collected during various campaigns; this high-resolution analysis may be therefore performed in other areas, in order to better understand the recent evolutionary history of the Adriatic basin.