EVOLUTION OF THE PYRENEAN AQUITAINE FORELAND BASIN (SW FRANCE)

International audienceThe Aquitaine basin is the retro-foreland basin associated with the Pyrenean orogen. It developed fromCampanian to Mid-Miocene by flexure of the upper (European) plate. The foreland basin forms a synorogenicsedimentary wedge up to 5.5 km thick in the south, thinning rapidly north. The synorogenic series migratesnorthward. The paleo-geographic history of the Aquitaine Basin shows an evolution from deep marine tocontinental facies. The continental to marine transition also migrates to the west. We study the spatio-temporalevolution of tectonic subsidence in the Aquitaine foreland basin, in order to understand the role of differentsources of subsidence at each stage of basin evolution. Our analyses show that the tectonic subsidence in theAquitaine Basin is a combination of flexural subsidence, caused by the Pyrenean orogen and dense mantlebodies within the upper crust, and post-rift thermal subsidence inherited from Early Cretaceous rifting. Thepost-rift thermal subsidence increases westward, reaching its maximum above inherited rift-basins (Parentisand Arzacq rift-basins). In the central Aquitaine Basin, two foreland successions are recognized, correspondingto distinct stages in the tectonic evolution of the Pyrenean orogenic system. The first succession (Campano-Maastrichtian) was deposited during the early inversion of the rifted domain. Early loading on the southernpart of the European plate was synchronous with post-rift thermal subsidence during this stage. The secondforeland succession (Eocene to Mid-Miocene) was deposited during main continental collision of the Pyrenees.These two foreland successions are separated by a Paleocene quiet phase. We show that the inherited thermalsubsidence strongly influenced facies distribution and the evolution of the flexural Aquitaine foreland basin