Estratigrafía y edad del Grupo Lena en el sector de Lois-Ciguera (Cuenca Carbonífera Central, NO de España)

Abstract

The stratigraphic succession of the Central Coal Basin (Cantabrian Zone, NW Spain) becomes increasingly more calcareous southeastwards. In the Lois-Ciguera sector, at its SE end, Iimestones are predominant, although they still alternate with siliciclastics. In this paper it is shown that most of the Carboniferous succession of this area belongs to the Lena Group. This lithostratigraphic unit has been previously known in other areas of the Central Coa! Basin and now is for the first time subdivided so in Iesser units that are provisionally described in an informal way: Yordas limestone, Lois shales, Bachende Iimestone, Dueñas Iutites and sandstones, Ciguera Iimestone and Anciles Iutites and Iimestones. The study of different fossil groups, mainly the fusulinid- fauna, shows that nearly the en tire Bashkirian and Moscovian of the Carboniferous System are represented in this series. Finally, a correlation is proposed between different parts of the basin. The comparison shows a striking decrease of thickness in a southeastern direction. The zone situated in the southeast end (the Lois-Ciguera sector) shows more clear and continuous marine conditions with characteristics typical of a shallow carbonated shelf.