Foraminíferos uniloculares calcáreos del Eoceno medio-superior y Oligoceno inferior, Isla Grande de Tierra del Fuego y plataforma continental adyacente, Argentina

Resumen

Unilocular calcareous Foraminifera of the middle-upper Eocene and lower Oligocene from Tierra del Fuego Island and adjacent continental platform, Argentina. The calcareous unilocular Foraminifera of the Leticia Formation (upper middle Eocene), Cerro Colorado Formation (upper middle Eocene-upper Eocene) and the Cabo Peña Formation (lower Oligocene) from Tierra del Fuego Island are described. The Leticia Formation yields scarce unilocular foraminifers that are characterized by species described from the Maastrichtian and the lower Eocene, including Conolagena argentina, C. acuticosta and Sipholagena sp. The Cerro Colorado Formation bears 29 species, almost the half of which (both individuals and species) belong to the Genus Fissurina, with Fissurina bisulcata occurring as the most abundant taxon. The formation also contains species characteristic of either Antarctic waters or the Malvinas current, reflecting the temperature decrease in the oceanic waters during the middle-late Eocene. The Cabo Peña Formation, which contains the Spirosigmoilinella-Martinottiella Assemblage typical of the Antarctic region, yielded 19 species; the dominant unilocular species belong to the genera Fissurina and Parafissurina, and the most conspicuous are fimbriate forms, such as F. fimbriata and F. fueguina, which are associated with Antarctic waters.