Post-Jurassic brittle deformation of Lusitanian Basin in the context of W Iberia evolution

A detailed structural analysis of the fracture network exposed in the Jurassic strata is used to reconstruct the Lusitanian Basin's brittle tectonic history related to the Meso-Cenozoic paleostress trajectories of the Iberian plate. Structural analysis is made by high-resolution virtual outcrop models and orthophoto mosaics, along with information obtained in the field. The paleostress regime is determined based on the fault-slip inversion method. Structural features are predominantly NNE-SSW, NE-SW and NW-SE-trending extensional fractures, including joints, veins, normal faults, and similar to E-W-oriented strike-slip faults. These structures remained active in the early basin evolution and were repeatedly reactivated by shearing and contraction. The chronological succession and paleostress reconstruction revealed three tectonic regimes (i) NE-oriented extension, (ii) NE-oriented strike-slip and (iii) NW-shortening. The first stress regime was driven by the North Atlantic rift propagation in the Iberia's west and northwest margins in the Late Jurassic-Early Cretaceous. The younger stress states involve reactivation and inversion of pre-existing fractures by Africa-Europe convergence since the Late Cretaceous. The findings are consistent with the regional stress field which the Iberian plate has experienced since the Meso-Cenozoic.