A refined calcareous nannofossil biostratigraphy for the middle Eocene–early Oligocene Southern Ocean ODP sites

This work presents the stratigraphic distribution of several species of calcareous nannofossil in the middle Eocene early–Oligocene from four Ocean Drilling Program (ODP) sites located between 60° and 65°S paleolatitude in the Southern Atlantic and Indian Oceans. Useful nannofossil datums that should facilitate construction of age-models and contribute to an integrated chronology for the upper Paleogene Southern Ocean sediments from ~ 42 to 33 Ma are summarized. The distribution patterns of calcareous nannofossils, studied by means of quantitative and semiquantitative methods, provide an improvement of the classical Southern Ocean biozonations, introducing new biostratigraphically useful biohorizons, and testing their reproducibility within and outside the region.