SEDIMENTARY MARKERS : A TOOL FOR THE QUANTIFICATION OF SUBSIDENCE AND ISOSTATIC MOVMENTS: EXEMPLES FROM THE OCCIDENTAL MEDITERRANEAN SEA

Abstract : Passive margins are characterised by an important tectonic and thermal subsidence, which favours a good preservation of sedimentary sequences. This sedimentation in turn enhances the subsidence because of loading effects. We present here a direct method based on sedimentary markers seen on seismic data, to evaluate total subsidence rates from the coast to the outer shelf and to the deep basin in the Gulf of Lion, from the beginning of massive salt deposition up to present day (the last circa 6 Ma) with minimal theoretical assumptions. The subsidence is organised in three compartments that are related to the very deep structure of the margin during the opening of the Liguro-provencal basin (Leroux et al., 2015). We also quantifed for the first time the Messinian salinity crisis isostatic rebound of the outer shelf (Rabineau et al., 2014). These very high total subsidence rates enable high sedimentation rates along the margin with sediments provided by the Rhône river flowing from the Alps, which in turn enable the detailed record of climate evolution during the Neogene that make the Gulf of Lion a unique archive (Rabineau et al., 2015). These results have been extended in 3D (Leroux et al., 2015) but also onland during Stéphane Molliex postdoc and towards the Valencia basin were similar measurements were undertaken (Pellen et al., 2016 ; Pellen et al., in progres).