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1 School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3YE, UK
2 Geology Department, Amgueddfa Cymru–National Museum Wales, Cathays Park, Cardiff CF10 3NP, UK
3 School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3YE, UK
4 Institute of Marine and Coastal Sciences and Department of Geology, Rutgers, The State University of New Jersey, 71 Dudley Road, New Brunswick, New Jersey 08901, USA
The Eocene-Oligocene (E-O) climate transition (ca. 34 Ma) marks a period of Antarctic ice growth and a major step from early Cenozoic greenhouse conditions toward today's glaciated climate state. The transition is represented by an increase in deep-sea benthic foraminiferal oxygen isotope (
18O) values occurring in two main steps that reflect the temperature and
18O of seawater. Existing benthic Mg/Ca paleotemperature records do not display a cooling across the transition, possibly reflecting a saturation state effect on benthic foraminiferal Mg/Ca ratios at deep-water sites. Here we present data from exceptionally well preserved foraminifera deposited well above the calcite compensation depth that provide the first proxy evidence for an
2.5 °C ocean cooling associated with the ice growth. This permits interpretation of E-O
18O records without invoking Northern Hemisphere continental-scale ice.
Key Words: Eocene Oligocene climate ice sheets temperature Cenozoic
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