Relative sea-level rise, sediment accumulation and subsidence in the Caorle Lagoon (northern Adriatic sea, Italy) during the Holocene

Abstract

The litho-biostratigraphic analysis and radiocarbon dating of the lagoon deposits found subsoil in the eastern Venetian plain (Portogruaro -Valle Vecchia borehole transect) has allowed the definition of the accretionary status of Caorle Lagoon and the accretion rate of deposits (AR). The knowledge of these two factors has permitted the evaluation of the relative sea level rise values of the coastal zone. For this estimation, has been used the relation which links the accretionary status of the lagoons to the accretion rate (AR) of tidal deposits and relative sea-level rise (RSL) proposed by Nichols (1989) has been used. The comparison of the various relative sea-level rise trends obtained from the deposits of Caorle and Marano Lagoons has demonstrated that significant variations exist between these lagoons, in a manner to be ascribed to different subsidence values which have affected the coastline of the Venice Gulf. Whilst proving these processes that influence the decrease of the soil level which exists in this zone, it is highlighted that the most recent contemporary deposits in Caorle lagoon show height differences, progressively increasing from the littoral zone to the hinterland deposits up to reaching maximum values of 2.8 m. Such variations correspond to the maximum absolute settling of the eastern Venetian coastal plain, recently reclaimed.