Resumen
The Santa María-Hualfín Basin in the NW Pampean Ranges started during the extensional faulting of a large NNW-SSE elongated dome, developed abo ve a peneplained basement. The faulted blocks were tilted outwards from the axis of the dome. Subsequently, the Neogene sedimentation (Santa María Group) was concentrated along listric faults bounding hemigrabens, reaching up to 3,000 m thick in these áreas. An intrabasin volcanic event occured during 11-6 Ma and was associated to asthenospheric upwelling and crustal thickening. A change from extensional to compressive tectonism, represented by the Intra-Aldalhuala disconformity, occurred at 4.8-5.2 Ma, resulting in approximately 9% shortening. Subsequently, during Pliocene times, thermal subsidence took place.