Estratigrafía y estructura del Antiforme del Ollo de Sapo en el área de Viana do Bolo-A Gudiña (Provincia de Orense, NO de España): nuevos datos sobre la posición estratigráfica de la Formación porfiroide Ollo de Sapo

Detailed mapping of the Viana do Bolo-A Gudina area furnished new data on the stratigraphy and structure of the Ollo de Sapo Antiform in the sector located between the Verin and Truchas synclines. The stratigraphic sequence is formed by several mappable lithological units that can be correlated with the Lower Cambrian-Upper Ordovician succession in the West Asturian-leonese Zone. The Ollo de Sapo formation is interbeded within the Upper CambrianLower Ordovician Cabos Series, which is consistent with the ca. 480 Ma isotopic ages recently obtained in other localities. The general structure of this antiform is characterized by the existence of kilometre-scale open folds with related subvertical crenulation cleavage, developed during the last variscan refolding event. These folds deform previous overturned and N-vergent folds, related with the first variscan deformation event. The whole area is affected by different variscan metamorphic and magmatic events. The strongest one is the high-T metamorphism associated with the intrusion of S-type two-mica granites that lead to partial melting in the metasediments and metavolcanics.