Thrusting and foreland basin evolution in the southern Pyrenees

The geometry and the infill of the south Pyrenean foreland basin mainly depend on the tectonic subsidence history due to the flexure of the crust, which in turn can be related to the structural evolution of the mountain chain at a crustal scale. Characteristics of the infill of the basin as well as the relationships between structures and synorogenic deposits allow distinction of four stages in the evolution of the south Pyrenean foreland basin. These stages can be related to the structural evolution of the crust as deduced from partial restored cross-section construction through the central Pyrenees. Stage I (Upper Cretaceous) is characterized by strong subsident turbiditic troughs deposited over a thinned crust. Uniform distribution of continental facies and a crust restored to its initial thickness corresponds to the stage II (Palaeocene). During Stage III, turbiditic troughs developed synchronously with the initial subduction of the lower crust (Lower and Middle Eocene). Stage IV (Uppermost Eocene-Oligocene) is characterized by continental deposition coeval with the increase of the crustal cross-sectional area, produced by both piggy-back and break-back thrust sequences