La Formación Ermita en el sinclinal de Vega de los Viejos

Abstract

The distinction amongst the Upper Devonian Nocedo, Fueyo and Ermita formations in the Vega de los Viejos Syn- cline (SW Cantabrian Zone) is controversial. Either the continuity of the stratigraphic record and the thickness of the Ermita Fm (a few metres vs several hundreds of metres) is a matter of debate. In this work, the basal unconformity of the Ermita Fm has been recognized by means of stratigraphic and structural data. In the area of study a time gap involving part of the Fras- nian and early Famennian has been detected on the basis of the presence of the brachiopods Atrypida indet. and Araratella sp below and above the unconformity, respectively . The Ermita Fm displays a variable thickness, rarely exceeding 20 m, and is organized into a composite fining-upward sequence made up of quartzarenites, calcareous sandstones and limestones with variable textures, including an uppermost crinoidal grainstone of Early Carboniferous age, also named as Baleas or Candamo Fm. All these variations are at least partly explained by the geometry of the basal unconformity (incised valleys). Additionally, the retrodeformation of the syncline shows that the unconformity angle is about 3º.