Detailed seismic-reflection and sedimentary study of turbidite sediment waves on the Var Sedimentary Ridge (SE France):: significance for sediment transport and deposition and for the mechanisms of sediment-wave construction

Sediment waves have been observed on the backside of levees in deep-sea turbidite systems where they are built by turbidity currents that spill out of channels and spread sediment over the levees. In an attempt to understand the way in which, sediment waves are initiated, prograde and/or aggrade, two sediment waves were selected within the present Var turbidite system (Ligurian Sea, north-western Mediterranean) for a detailed sedimentary study. The data include high-resolution seismic-reflection profiles, 3.5-kHz echo-sounder profile, high-resolution side-scan imagery and cores collected from the upstream flank, crest, and downstream flank of both sediment waves. Core-to-core correlations allow interpretation of the dynamic of gravity-flows across the sediment waves. The asymmetrical internal structure of the waves results from higher rates of sediment deposition on the upstream flank and lower rates of deposition and erasion on the downstream flank and further results from active progradation stages during periods of greater gravity-flow activity. The strong differences of depositional processes across the sediment waves result through time in the individualisation of large and interconnected sand bodies in the distal part of the levee. (C) 2001 Published by Elsevier Science Ltd.