Provisional geological map of the Southern Cantabrian Mountains (Spain)

The area is mainly covered by Carboniferous sediments. Only two Devonian structures are present. The Devonian yielded sufficient fossils from Eifelian up to Famennian but in the Carboniferous fossils are scarce. Permian and Triassic cover the area unconformably in the east. In the Carboniferous several formations of the Ruesga Group and the Yuso Group have been mapped. The base of the Yuso is marked by its basal conglomerate and its unconformable position upon the Ruesga. The divergency of directions of contemporaneous major folds in the map area is controlled by fundamental faults. Two folding phases can be distinguished; Asturian folds with steep axial planes are superposed upon Sudetic recumbent folds.