Multibeam backscatter as a tool for sea-floor characterization and identification of oil spills in the Galicia Bank

This study is focused on the potential of using the multibeam acoustic backscatter both for sea-floor characterization of the Galicia Bank and for identification of sea-bottom oil spills. An extended multibeam data set was acquired during the RG-1 and RG-2 surveys aboard RV Hespérides in 2003 for the geological and geophysical characterization of the Galicia Bank, where the oil tanker Prestige wreck is located. 3-D images have been made by integrating bathymetry and backscatter data. Multibeam data have been additionally supported by gravity core information in order to correlate sea-floor acoustic backscatter with the surficial sediments and their physical properties. The major factors that seem to control the zonation of the backscatter intensity images are (i) the type of the sedimentary processes (gravitational, turbiditic, hemipelagic), which control at the same time, the grain size distribution, and (ii) the sea-bottom morphologies, such as basement outcrops. However, there are some backscatter halos that cannot be explained by these processes. In the backscatter maps, the bow and stern of the Prestige wreck are clearly marked by a high-backscatter intensity anomaly, whose existence is discussed.