Foraminíferos del Aaleniense en el sector suroccidental de la Cuenca Vasco-Cantábrica

Abstract

Uppermost Toarcian and Aalenian foraminiferal assemblages from Cillamayor and San Andrés Sections (southwest sector of the Basque-Cantabrian Basin) have been studied. These sections show some differences about facies and thickness. Cillamayor section would be located near the margin basin, while San Andrés section would be situated in a more distal zone in the platform. 53 foraminiferal species belonging to 5 suborders have been identified. In both areas Lagenina is the best represented suborder. All the foraminiferal assemblages are dominated by Vaginulinidae, genus Lenticulina. The number of specimens and identified species is larger at Cillamayor section than San Andrés section. Uppermost Toarcian assemblages are poor. Diversity increases from Opalinum Biozone in San Andrés section and from Murchisonae Biozone at Cillamayor section. From the middle of Bradfordensis Subzone the assemblages become poor in both areas. The stratigraphical ranges of common species are similar, but there are differences in some taxa; the first appearance of some species is delayed in Cillamayor section (Nodosaria fontinensis Terquem, Lenticulina exgaleata Diem...). No Tethysian taxa have been found; all the foraminiferal assemblages are "boreals".