Distribution, morphology and triggers of submarine mass wasting in the Sea of Marmara

An overview is given of mass wasting features along the slopes of the Sea of Marmara, Turkey, based on new data and previously published information. The Sea of Marmara is characterized by active tectonics along the North Anatolian Fault and by eustatic sea level changes controlling the connections both to the Mediterranean and Black Sea (i.e. lacustrine and marine conditions during sea-level low and high stands, respectively). High resolution bathymetric data, subsurface echo-sounder and seismic reflection profiling, seafloor visual observations, as well as stratigraphic analysis of sediment cores have been used to identify, map and date submarine slope failures and mass wasting deposits. Gravity mass movements are widespread on the steep slopes of the Sea of Marmara, and range from small scale slope failures, mainly located within the canyons, to wider unstable areas (20 to 80 km2). The largest mass wasting features, i.e. the Tuzla, Ganos and Yalova complexes, have been analyzed in connection with crustal deformation. These gravitational gliding masses are probably induced by the transtensional deformation within the crust. Moreover, age determination of landslides and debris flows indicate that they were more frequent during the last transgressive phase, when the rate of terrigenous sediments supplied by the canyons to the deep basin was higher. We discuss these results taking into account activity, pre-conditioning and trigger mechanisms for slope instability with respect to tectonics and paleo-environmental changes induced by sea-level oscillations.