EVOLUTION OF THE PYRENEAN AQUITAINE FORELAND BASIN (SW FRANCE)
Abstract
The Aquitaine basin is the retro-foreland basin associated with the Pyrenean orogen. It developed from
Campanian to Mid-Miocene by flexure of the upper (European) plate. The foreland basin forms a synorogenic
sedimentary wedge up to 5.5 km thick in the south, thinning rapidly north. The synorogenic series migrates
northward. The paleo-geographic history of the Aquitaine Basin shows an evolution from deep marine to
continental facies. The continental to marine transition also migrates to the west. We study the spatio-temporal
evolution of tectonic subsidence in the Aquitaine foreland basin, in order to understand the role of different
sources of subsidence at each stage of basin evolution. Our analyses show that the tectonic subsidence in the
Aquitaine Basin is a combination of flexural subsidence, caused by the Pyrenean orogen and dense mantle
bodies within the upper crust, and post-rift thermal subsidence inherited from Early Cretaceous rifting. The
post-rift thermal subsidence increases westward, reaching its maximum above inherited rift-basins (Parentis
and Arzacq rift-basins). In the central Aquitaine Basin, two foreland successions are recognized, corresponding
to 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 southern
part of the European plate was synchronous with post-rift thermal subsidence during this stage. The second
foreland 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 thermal
subsidence strongly influenced facies distribution and the evolution of the flexural Aquitaine foreland basin.