The bottom ofVillarroya de los Pinares formation, that is, the bottom of Upper Aptian D.S., is made up of terrigenous sediments. These materials show a retrogradational vertical evolution. This evolution started with fluvial channel facies, continuing later with tidal channel facies and finally this evolution finished with shoals facies. These sediments form the low system track of the Upper Aptian D.5. and they are represented in all basin. The continental enviroment sediments are distributed mainly at the western part of the basin and the sea dynamic action is represented at the central and eastern areas of the basin