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tel-00790852, version 1 - 21 Feb 2013 <strong>Quantification</strong> of Pliocene-Quaternary Subsi<strong>de</strong>nce and isostatic readjustment re<strong>la</strong>ted to the Messinian Crisis (using paleobathym<strong>et</strong>ric markers in the Gulf of Lion) M. Rabineau(1), E. Leroux(1, 3), F. Bache(2), D. As<strong>la</strong>nian(3), C. Gorini(4), M. Moulin(5), S. Molliex (1), L. Droz (1), T. Dos Reis(6), JL Rubino (8), JL Oliv<strong>et</strong>(3) Abstract CNRS, UMR6538, Domaines Océaniques, IUEM, 29280 Plouzané, France IFREMER, DRO/GM,BP 70, 29280 Plouzané, France (2012) The sedimentary record of the offshore part of continental margins is characterized by an important tectonic and thermic subsi<strong>de</strong>nce, which favours a good preservation of sedimentary sequences (as opposed generally to the onshore part of margins). This sedimentation in turn enhances the subsi<strong>de</strong>nce because of loading effects. The quantification of this total postrift subsi<strong>de</strong>nce and more specifically <strong>de</strong>ciphering the re<strong>la</strong>tive effect of the different factors is not easy, especially when no wells are avai<strong>la</strong>ble in the area. We present here a direct estimation based on the geom<strong>et</strong>ry and the interpr<strong>et</strong>ation of sedimentary markers as seen on seismic data, in the Gulf of Lion, to evaluate total subsi<strong>de</strong>nce rate from the coast to the outer shelf and in the <strong>de</strong>ep sea from the end of Messinian to present day (the <strong>la</strong>st circa 5.6 Ma) with minimal assumptions. On the shelf, the Pliocene-Quaternary subsi<strong>de</strong>nce shows a seaward tilting reaching a rate of 240-260 m/Ma at the shelf break (70 km from the present day coastline), i.e. a total angle of rotation of 0.88°, with a hinge point (rotation point) located 13 km <strong>la</strong>ndward of present day coastline (around Sète city). This rate is the same as the rate calcu<strong>la</strong>ted for the <strong>la</strong>st 500,000 years at 70 Km (Rabineau <strong>et</strong> al., 2006, 2007). This suggests that subsi<strong>de</strong>nce rate has been constant <strong>du</strong>ring the Pliocene-Quaternary, creating, continuously and regu<strong>la</strong>rly a <strong>la</strong>rge amount of accommodation to be filled by
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