Cooling and ice growth across the Eocene-Oligocene transition

• Published in: Geology
• Main Authors: Lear, Caroline Helen, Bailey, Trevor R., Pearson, Paul Nicholas, Coxall, Helen Kathrine, Rosenthal, Yair
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Geological Society of America 2008
• Subjects: GC Oceanography; QE Geology; Antarctic; Antarc*
• Online Access: https://orca.cardiff.ac.uk/id/eprint/10101/; https://doi.org/10.1130/G24584A.1

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.