Geomorphological characterization and marine geohazard assessment of mass transport deposits in the Graham Bank (Sicily Channel, Central Mediterranean)
摘要
Subaqueous gravity-driven mass movements and their resulting mass transport deposits (MTDs) are primary agents in shaping continental margins and volcanic edifices. This study provides a high-resolution geomorphological and geophysical characterization of MTDs in the Graham Bank, a complex setting in the Sicily Channel (Central Mediterranean) where active rifting, anorogenic volcanism, and vigorous oceanographic circulation converge. High-resolution multibeam bathymetry (5 m grid) integrated with sub-bottom CHIRP seismic profiles documents a complex seafloor shaped by the interaction of tectonics, volcanism, and oceanographic processes at water depths between ~ 10 and 350 m. We mapped and classified a diverse spectrum of deposits into three thematic categories: (i) large-scale volcaniclastic debris avalanches (up to 2.2 km2 and thicknesses exceeding 20–30 m) characterized by blocky topography and amphitheater scars; (ii) tectonically-controlled rockfalls at the foot of steep escarpments; and (iii) soft-sediment deformation structures (slumps and channelized-fills) showing mounded hummocky facies and basal erosional unconformities. These features are variably distributed across three main physiographic domains: the volcanic sector, a fault-bounded erosive channel, and an adjacent flat outer-shelf area. Our findings suggest a conceptual "cascading" morphogenetic framework where tectonic rifting with NW–SE-oriented normal faulting and high regional heat flow (75–100 mW/m2) pre-condition the slopes, while regional seismicity (ML ≥ 5) and bottom-current erosion (Atlantic Ionian Stream) act as possible transient destabilizing mechanisms. Volcanic-driven instabilities may be related to volcanic activity; the 1831 eruption illustrates the system’s capacity for rapid morphodynamic change, though direct temporal links to individual MTDs cannot be established without sediment dating. The Graham Bank thus represents a high-instability environment where MTDs record the combined effects of internal geodynamic forcing and external oceanographic modulation, providing a key natural laboratory for assessing gravity-driven processes. The proximity of these features to submarine cables and pipelines, coupled with the recent volcanic history of the area (e.g., the 1831 eruption), underscores a preliminary geohazard concern warranting further investigation in this sector of the Mediterranean.