Mass wasting dynamics at the deeper slope of the Ligurian Margin (Southern France)

Abstract

Submarine landslides are very common on the tectonically and seismically active Ligurian margin, NW-Mediterranean Sea. We present geophysical, sedimentological and geotechnical results from two extensive landslide complexes in water depth exceeding 1, 500 m on the steep continental slope (> 11°) near the Var Canyon. At the Western Landslide Complex, facing the Var Canyon, we observe multiple headwalls and tilted layering. Undisturbed and failed sediments are characterised by a downward increase in bulk density and shear strength, the failed portion of which shows low intrinsic friction coefficients of 0.27. Otherwise, at the Eastern Landslide Complex, which shows smooth headwall features containing debrites and hemipelagic silty clays with pebbles, we observed constant bulk density of the failed sediments; however the shear strength in the remobilized sediment is lower than in the hemipelagites. This indicates that the failed material may have incorporated seawater and has retained its underconsolidated state until the present. The material is hence prone to future landsliding in case of seismic loading and/or the occurrence of other factors destabilizing the sediment. © Springer Science + Business Media B.V. 2010.