Searching for the Record of Historical Earthquakes, Floods and Anthropogenic Activities in the Var Sedimentary Ridge (NW Mediterranean)

Abstract

Submarine landslides on continental slopes are triggered by diverse mechanisms such as sea-level variations, climate-driven sediment supply fluctuations, slope steepening related to long term tectonics, earthquakes and human activities. In the present work, we try to discriminate the origin of major gravity events recorded in three sediment cores collected on the Var Sedimentary Ridge (NW Mediterranean) by means of X-ray imaging, grain-size distributions and 210Pb-based chronologies supported by 137Cs and AMS 14C dating. An alternation of hemipelagic mud and sandy turbidite layers is apparent in all cores. In two of them, the topmost turbidite can be correlated to the well-known 1979 Nice-Airport land slide. A sub-surficial sandy layer is identified in all three cores with an approximate age of 120 years, suggesting for the first time a relationship with the largest earthquake in the region (1887; MwD6.9). Below the depth of that major event, sand beds are tentatively related to older local earthquakes and centennial floods