The Viveiro fault is a ductile normal fault of Hercynian age which separates two distinct lithological units metamorphic evolution and tectonic styles. The foot wall in the east forms the Lugo dome, made with diferent Cambrian and pre-Cambrian metasediments with dominant flat-lying foliation and E-W trending stretching lineation. The hanging-wall in the west consist of a domain of tight upright folds with associated west dipping dominant foliation. An upright synform with a core of Silurian rocks is pinched between the Viveiro fault and the westerly located complex Olio de Sapo antiform