Quantification de la subsidence et du réajustement isostatique messinien à partir de paléomarqueurs sédimentaires : exemples en Méditerranée Occidentale

Marina Rabineau (1) , Romain Pellen , Estelle Leroux (1) , Daniel Aslanian (2) , Stéphane Molliex (1) , Malyline Moulin , Christian Gorini (3) , François Bache (3) , Laurence Droz (1) , Antonio Tadeu dos Reis (4) , Jean-Loup Rubino (5) , François Guillocheau (6)

1 LDO - Domaines Océaniques
2 GM - Géosciences Marines
3 iSTeP - Institut des Sciences de la Terre de Paris
4 Departamento de Oceanografia Geológica - Faculdade de Oceanografia
5 TOTAL S.A.
6 GR - Géosciences Rennes

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. On the shelf, the Pliocene-Quaternary subsidence shows a seaward tilt reaching a rate of 240 m/Ma ( 15 m/Ma) at the shelf break (70 km from the present day coastline) (i.e. a total angle of rotation of 0.88°(0.16°/Ma).We also quantifed for the first time the Messinian salinity crisis isostatic rebound of the outer shelf. This value is reaches up to 1.3 km of uplift during the crisis around the Herault-Sète canyon heads (around 1.8 km/Ma). On the slope, we also find a seaward tilting subsidence from Km 90 to Km 180 with a measured angle of 1.41°. From 180 Km to the deepest part of the basin, the total subsidence is then almost vertical and reaches 960 m/Ma ( 40 m/Ma) during the last 5.7 Ma ( 0.25 Ma) in the deepest part of the basin. The subsidence is organised in three compartments that seem related to the very deep structure of the margin during the opening of the Liguroprovencal basin. 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 Pliocene-Quaternary that make of the Gulf of Lion a a unique archive. These results have been extended in 3D during Estelle Leroux PhD but also onland during Stéphane Molliex postdoc and towards the Valencia basin were similar measurements are under process within Romain Pellen PHD (see their respective presentations).

Domains: Earth Sciences

Marina Rabineau, Romain Pellen, Estelle Leroux, Daniel Aslanian, Stéphane Molliex, et al.. Quantification de la subsidence et du réajustement isostatique messinien à partir de paléomarqueurs sédimentaires : exemples en Méditerranée Occidentale. 24 ème Réunion des sciences de la Terre 2014, Oct 2014, Pau, France. pp.75. ⟨insu-01080496⟩