Uruguay geology contributions no.1

The regional schistosity is the result of the superposition of three deformation phases. The phase generated a metamorphic S1, developing isoclinal folding. Generally, S1 is normal to original stratification, So. At regional level is recognized a mineralogical lineation at foliation planes: Lr. to Owing 1101- So is systematically placed at the same plane with S1 (There is a transposition phenomena So-1). phase Il the structures are controlled by the mechanics properties of the rocks. In uncompetents and anisotropic rocks, schistosity S2 corresponds to a fracture schistosity or to a fracture-folding schistosity. At competent rocks S2 is less penetrative, generating a parallel fracture systeme. Limestones develop metric, isopaque, isoclinal or asymmetric folds. Meanwhile in phyllites are observed kink or chevron folding. Boudinages phenomena were also seen in isoclinal folds. A second lineation is develop as a consequence of S2 intersection with So-1. The phase III is developed near to major tectonic accidents and is characterized by a second fracture schistosity (S3) which deforms S2. Megastructures corresponds fundamentally to phases II and III, and only some originated by phase I are preserved. Phase II megastructures are represented by fracturation with inverse faulting and dextral shearing. The regional rnetarnorphism is contemporaneous with phase I.