Evolución tectónica del borde oriental de la Cuenca del Viar (Zona Sudportuguesa)

Laburpena

The Viar Basin is filled up by molasse-type detritic fluvial and lacustrine sediments, interbedded with basic lava flows. The lower levels have abundant fossil flora of Autunian age (Lower Permian). The eastern Viar Basin margin is coincident with the boundary between the Ossa-Morena and South-Portuguese zones (Spanish Iberian Massif). This boundary is a brittle shear zone marked by the development of reverse faults and thrusts. The main thrust dips to the northest. A cylindrical fold appears in the footwall to the main thrust (Viar Basin). The upward movement of the hanging wall produced the erosion of the Permian cover materials. The process of brittle deformation took place during the Autunian and later on, and finished with the superimposition of the Ossa-Morena zone on the Viar Basin. The fault analysis does not record major changes in the orientation of the paleostress axes (two of the main stress axes are horizontal, one of them with a NE-SW trend, and the third one is vertical), but only the exchange of relative values of these axes. These data are consistent with an extensional episode during the Autunian with a NE-SW extension and a post-Autunian compressional episode, that gave place to the Viar reverse fault and with a NE-SW orientated compressional axis.