Mappable units of the Carboniferous in the Southern Cantabrian Mountains (NW-Spain)

Distinct general lithological features, separated by unconformities, serve to distinguish three groups of mappable formations in the Carboniferous of the area, the Ruesga Group, the Yuso Group and the Cea Group. The formations which compose the Ruesga Group can be found in the greater part of the area. In general they start with a limestone series developing upwards and laterally into greywackes. The conglomerates and molasse greywackes formations of the Yuso Group follow and are limited by two major structural zones; in the west the zone that runs over the Pardomino Ridge and the Pontón fault line and in the south the León line. West of the “Pardomino-Pontón” zone other formations have been mapped, but the information is still insufficient for a good correlation of the depositions on both sides of that zone. The mainly continental formations of the upper Cea Group occur mostly in unconformable intramontane basins. In the easternmost part of the area the unconformity is only locally present.