STRUCTURAL STYLE AND EVOLUTION OF THE GULF-OF-LION OLIGOMIOCENE RIFTING - ROLE OF THE PYRENEAN OROGENY

The Gulf of Lion margin results from the Oligo-Aquitanian rifting and Burdigalian crustal separation between continental Europe and Corsica-Sardinia. Immediately before the onset of extension, the area of the Gulf of Lion was affected by the Pyrenean orogeny which controlled the structural style of the evolving margin. During extension, the foreland of the Pyrenean orogen was affected by extensional thin-skinned tectonics. The decollement level ramped down into the basement, in areas where the latter was thickened during orogeny. In this intermediate part, the margin was extended by several crustal-scale low-angle faults, which generated small amounts of syn-rift sedimentation compared with the accumulation of post-rift sediments. However, more than 4 km of syn-rift sediments were deposited in the Camargue basin, which is located at the transition between thin- and thick-skinned extensional systems. Kinematic restorations and stratigraphy suggest a pre-rift surface elevation above sea-level of at least 1 km in the intermediate part of the margin, which is in agreement with reduced syn-rift sedimentation. The slope area extends seaward of the North Pyrenean Fault, a terrane boundary inherited from the Pyrenean collision. This part of the margin was stretched by seaward dipping low-angle block tilting of the upper crust, and antithetic lower crustal and sub-crustal detachment. The lithospheric structures inherited from the Pyrenean orogeny exerted a strong control on the kinematics of the rifting and on the distribution and history of subsidence. Such parameters need to be integrated in the definition of pre-rift initial conditions in future basin-modelling of the Gulf of Lion.