Tethys-Atlantic Interaction Along the Boundaries of the Iberian Plate: Pyrenees and Betics Mountain Belts

10th Alpine workshop "CorseAlp2011", 10-16 April 2011, Saint-Florent (Corsica)Detailed movements of small tectonic plates between larger plates have been difficult to assess due to their facility to move independently of those limiting plates and because the frequent vertical axis rotations they experienced during their evolution. The Iberian plate, located at the western boundary of the Tethys Ocean, is one of these conflicting plates. As has been pointed out in several published works the combined study of large scale plate motions together with field based results along plate boundaries must constrain as much as possible their evolution. The feedback between these two different scales of work should provide a better understanding of the evolution of the Iberian plate although there are still large conflicting areas and time periods that need to be understood. In this paper we try to discuss field observations from the Pyrenees and Betics within the frame of published large scale Iberian plate reconstructions. Starting in the Early-Middle Jurassic times the central Atlantic connected to the Alpine-Tethys separating Iberia from the north of Africa. The Iberia-Africa boundary resulted in a segmented margin characterized by a thinned crust with strong and multiple evidences of upper mantle exhumation and formation of oceanic crust (e.g., Schettino and Turco 2010). The northern propagation of the Northern Atlantic in Early Cretaceous times produced the abandonment of the Alpine-Tethys but the opening of the Bay of Biscay along the already rifted Pyrenean corridor with the concomitant counterclockwise rotation of Iberia. Upper mantle rocks were exhumed along the western side of the Pyrenees in the eastern oceanic crust pinpoint (e.g., Jammes et al., 2010). Further northern propagation of the North Atlantic Ocean also produced the end of the Pyrenean transtension close to the Early to Late Cretaceous boundary. The Iberian plate was thus an independent plate when Africa started northwards convergence against Eurasia during the youngest part of the Late Cretaceous (Santonian to Maastrichtian). During this northwards convergence the two Iberian plate boundaries closed producing the Pyrenees and the Betics (Betic-Rif system). The Pyrenees show double vergence and about 150 km of shortening and a partial north-dipping subduction of Iberia beneath Europe that is clearly imaged in the ECORS crustal seismic profile (e.g., Choukroune et al., 1989). The foreland developed as under filled and marine from Late Cretaceous to the latest middle Eocene time at about 36 Ma and then overfilled and continental from deposition of the Cardona evaporitic level to the end of shortening during the Oligocene (e.g., Verges et al., 2002). The end of deformation determined by magnetostratigraphy on growth strata attached to the front of the Pyrenean fold-and-thrust belt occurred during upper Oligocene times (~24.7 Ma) although major basement fast uplift, determined from fission track cooling ages in central Pyrenees, ended at about 30 Ma followed by a much slower rate up to about 25 Ma (e.g., Metcalf et al. 2009)