| Summary: | The Eocene-Oligocene transition (EOT, ~34 Ma) is marked by changes in calcareous nannofossil assemblages and coincides with variations in sea-surface temperature and nutrient availability. During the EOT, calcareous nannofossil assemblages underwent an abrupt turnover with a permanent decline of warm-oligotrophic taxa, a decrease in species diversity and a remarkable increase in eutrophic taxa. Here, we combined calcareous nannofossil and planktonic foraminifera biostratigraphy from ODP Hole 756C (Ninetyeast Ridge, Indian Ocean), as well as new benthic foraminifera and bulk sediment stable isotope (C, O) records, which documents ocean-climate changes and provides independent chemostratigraphy. Our results provide further support to previous records documenting an invigorated Southern Ocean circulation associated with the transport of cooler and nutrient-enriched waters toward low-middle latitudes.
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