The use of high-resolution elevation histograms for mapping submerged terraces: Tests from the Eastern Tyrrhenian Sea and the Eastern Atlantic Ocean

Abstract Histogram plots can be used as a cost- and time-efficient tool to detect horizontal or gently dipping geomorphic surfaces within a background regional topography. One of the main classes of these surfaces is typified by terraces formed during marine still-stands. This contribution uses elevation histogram plots as morphometric indicators for detecting the possible existence of concealed terrace orders in Digital Elevation Models (DEMs) derived by the processing of bathymetric data. The approach is particularly useful when dealing with submerged terraces and platforms, because of the obvious difficulties in mapping those surfaces. The advantage of using this indicator consists in the rapid identification of DEM recurrent bathymetric values. This tool is most powerful when dealing with shortly developed terraces and/or multiple terrace orders, whose detection could have been missed by direct observation. Two case studies characterized by the presence of a single terracing event are tested: the southern slope of the Ischia Island and the top of the Palinuro Seamount, both located in the Eastern Tyrrhenian Sea Margin. Elevation histograms are used for terrace order computation in a more complex setting, the Gorringe Bank, located offshore SW Portugal in the Eastern Atlantic Ocean. The results show that a joint use of elevation histogram computation and geomorphologic analysis can be particularly efficient in the study of planar surfaces.