Unexpected fast rate of morphological evolution of geologically-active continental margins during Quaternary: Examples from selected areas in the Italian seas

In the last few decades, seafloor imagery systems have drastically changed our vision of a mostly regular and depositional marine landscape, evidencing how erosive and mass-wasting processes are widespread in the marine environments, with particular reference to geologically-active areas. Most of the previous studies have focused on the characterization of these features, whereas a very few ones have tried to estimate what is the extent and order of magnitude of erosion rates in these areas. In this paper, we show several examples from some of the most geologically-active margins off Southern Italy aimed to a) quantify the spatial extent of such processes, b) better understand the role of submarine erosion in the morphogenesis of the coastal sector, and c) try to roughly estimate the order of magnitude of erosion rates in these areas. The results are impressive, with mass-wasting features widespread from coast down to 2600, affecting from the 52% up to 97% of the whole continental slope. Because of the narrow or totally lacking shelves in these areas, mass-wasting processes often occur close to the coast and match embayment of the coast, so indicating a key role in the morphogenesis of coastal sector, with significant implication on the related geohazard. Finally, based on a morphological approach integrated by available stratigraphic constraints we have roughly estimated average erosion rates in these areas, ranging from (at least) some mm/year to a few cm/year, i.e., some hundreds of meters up to kilometers eroded in each eustatic cycle. Despite the large uncertainties of these estimates as well as their spatial and temporal variability in response to regional and local factors, the obtained values are very high and they should be considered for future model of margin evolution, source-to-sink computation and marine/coastal geohazard assessment. (C) 2017 Elsevier Ltd. All rights reserved.