Landsliding analyses at site GeoB14401 and GeoB14403, NE Gela Basin, Strait of Sicily, Mediterranean Sea

This study uses an integrated chronological framework from two MeBo boreholes and complementary ultra-high-resolution acoustic profiling in order to assess (1) the frequency of submarine landsliding at the continental margin of NE Gela Basin and (2) the associated mechanisms of failure. Accurate age control was achieved through absolute radiocarbon dating and indirect dating relying on isotope stratigraphic and micropaleontological reconstructions. A total of nine major slope failure events have been recognized that occurred within the last 87 kyr (~10 kyr return frequency), though there is evidence for additional syn-depositional, small-scaled transport processes of lower volume. The majority of recognized events occurred during conditions of sea level fall and lowstand. Preferential failure involves translational movement of mudflows along sub-horizontal key surfaces that are induced by sedimentological changes relating to pre-failure stratal architecture. Along with sequence-stratigraphic boundaries reflecting paleoenvironmental fluctuations, intercalated volcanoclastic layers are shown to be key to the basal confinement and lateral movement of these events. Another major predisposing factor in this area is given by rapid loading of fine-grained homogenous strata and successive generation of excess pore pressure, as expressed by several fluid escape structures. Recurrent failure, however, requires repeated generation of favorable conditions and seismic activity, though low in this area if compared to many other Mediterranean settings, is shown to represent a legitimate trigger mechanism.