Pyrenean orogeny and plate kinematics

The evolution of the Pyrenees, a mountain range between Iberia and Eurasia, has remained the subject of many debates between geologists and geophysicists for a long time. By combining the identification of seafloor spreading anomalies A33o to M0 in the Bay of Biscay with those in the North Atlantic, we have derived a position of a mean pole of rotation for the entire opening of the Bay of Biscay. Four hundred kilometers of shortening took place between the Iberian and Eurasian plates in the Pyrenean domain during the opening of the Bay of Biscay, from chrons M0 to A33o time (118 to 80 Ma). The deep seismic Etude Continentale et Oceanique par Reflexion et refraction Sismique (ECORS) profile shot across the Pyrenees and teleseismic data show the presence of two distinct slabs, which dip to the north. The southern slab is linked to the subduction of the neo-Tethys Ocean, which was created from late Jurassic to early Aptian. Simultaneously, elongated back arc basins formed along the future Pyrenean domain. This slab was active from at least 118 Ma ( early Aptian) to 100 Ma (late Albian). The northern slab, active since 85 Ma, is linked to the subduction of the lower continental crust located south of the Pyrenean domain. In the upper crust, normal faults as well as the north Pyrenean fault became reverse faults, and former back arc basins were inverted, giving rise to the uplift of the Pyrenees as a double asymmetrical wedge.