Fusulines of the Hoyo Oscuro section, Ándara massif of Picos de Europa (Cantabrian Zone, N Spain). New constraints about the onset of the Variscan deformation

Abstract

The Hoyo Oscuro section (Ándara Massif, southeastern part of Picos de Europa) is a comparatively small exposure of Pennsylvanian syntectonic deposits that shown angular unconformity on the fairly extensive pre-tectonic carbonate platform strata of Pennsylvanian age accumulated in the distalmost realms of the Variscan foreland basin of the Cantabrian Zone. Fusuline-bearing strata from this section yielded species belonging to the genera Pseudostaffella, Ozawainella, Fusulinella, Protriticites, Pseudotriticites, Fusulina and Quasifusulinoides; one of these forms, Protriticites schulzei Villa, is described as a new species from the Cantabrian Mountains. Fusuline assemblages allow us to correlate the Hoyo Oscuro strata with the syntectonic successions of the northern part of Picos de Europa (Gamonedo area) and with specific intervals of the Picos de Europa Formation that, according to currently accepted models, were pre-tectonic. The age data obtained for the oldest syntectonic deposits of the studied section are of key importance, since they constitute a new anchor point confirming the onset of the Variscan Orogeny in this part of the Cantabrian Zone.