Failure processes and gravity-flow transformation revealed by high-resolution AUV swath bathymetry on the Nice continental slope (Ligurian Sea)

Abstract

International audienceThe continental slope offshore Nice is a natural laboratory to investigate submarine landslides and gravity-flow processes. Using EM300 bathymetry data (spatial resolution of 25 m), about 250 scars with volume less than 8 × 108 m3 were identified. The AUV bathymetric data (spatial resolution of 2 m) revealed a greater number of scar-related failures with two main morphologies: some scars are affected by retrogressive processes of erosion, suggesting failures were triggered a long time ago, while other scars exhibit no evidence of post-failure erosion, suggesting they could have been triggered recently. Downslope from the scars, there are scattered blocks, on average 5-m high and 40-m wide, and well-developed asymmetrical waves, on average 2-m high and 20-m in wavelength. Such evolution could be evidence for the transformation of the remobilized deposits into cohesive flows then turbulent flows. Such transformation took place over a distance of less than 6-8 km