Census of calcareous nannofossil taxa expressed as percent of total number of individuals counted, ODP Legs 113, 114, 119, 120

• Main Author: Wei, Wuchang
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1991
• Subjects: 113-689; 114-699; 114-703; 119-744; 120-748; COMPCORE; Composite Core; Indian Ocean; Joides Resolution; Leg113; Leg114; Leg119; Leg120; Ocean Drilling Program; ODP; South Atlantic Ocean; South Indian Ridge; South Indian Ocean; Southern Ocean
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.712626; https://doi.org/10.1594/PANGAEA.712626

Quantitative analysis of upper Eocene-upper Oligocene calcareous nannofossil assemblages from five Ocean Drilling Program sites in the Atlantic and Indian Ocean sectors of the Southern Ocean reveals an abrupt increase in cool-water taxa at the top of magnetic Subchron C13R ca. 35.9 Ma, coincident with an enrichment of ~1‰ d18O in the planktonic foraminifers at these sites. The synchrony of the abrupt increase in cool-water taxa in the Southern Ocean renders this event a useful biostratigraphic datum at southern high latitudes. This earliest Oligocene cool-water taxa increase was the sharpest and largest during the late Eocene-late Oligocene interval and indicates a drop in surface-water temperature of more than 3°C in the Southern Ocean. This suggests that the earliest Oligocene d18O shift represents primarily a temperature signal; a small portion (~0.2‰) is attributable to a global ice-volume increase.