Lithostratigraphy and subdivision of the Fueyo Formation (Famennian, Upper Devonian) in the Bernesga valley, southern Cantabrian Mountains, Spain

This study presents an analysis of the Famennian (Upper Devonian) Fueyo Formation of the southern Cantabrian Mountains. The stratigraphic position of the Upper Devonian Unconformity in the External Zone of the Asturo-Leonese facies domain has been changed from the base of the sandstone unit overlying the Fueyo shales to the uppermost part of the sandstone unit. This revision leads to a re-interpretation of the Famennian succession, and the formal introduction of a new lithostratigraphic unit, the Santas Martas Formation. This study outlines the stratigraphic features and spatial distribution of these revised and newly established units.