Estructura de inversión tectónica positiva en la cuenca de Anayet (Pirineos Centrales, Huesca)

Zusammenfassung

During Stephanian-Permian times, pull-apart basins were generated around the Axial Zone of the Pyrenees. The Anayet basin lies between the Tena and Aragón valleys in the Western Spanish Axial zone showing an WNW-ESE-trending elongated shape (10 km long and 3 km wide). It is filled by a detrital succession that unconformably overlies a substratum made by Middle Devonian slates and Carboniferous sandstones and slates (“Culm” facies) in the E and, Carboniferous limestones and “Culm” facies, in the W. This basal contact is, for most of its extent, unconformable but, near the Aragón River, it is repolaced by a fault dipping 60º to the N that places Permian rocks, in the hangingwall, over Carboniferous limestones, in the footwall. The fault contact is a 3 m-thick shear zone that develops breccias, fault gouges and sigmoidal S-C tectonites indicating a reverse motion. This, together with the high dip of the contact and the presence of younger rocks in the hangingwall suggests that originally the contact was a normal fault that limited the Anayet basin to the S. This normal fault was reactivated as a high-angle reverse fault during the positive inversion tectonics induced by the Alpine Orogeny.