NOAA/WDS Paleoclimatology - Prydz Bay, East Antarctica 36-33ma Biomarker Data and Climate Reconstructions

The Eocene-Oligocene Transition (EOT) marks the onset of Antarctic glaciation at 33.7 Ma. Although the benthic d18O record defines the major continental ice sheet expansion, recent sedimentary and geochemical evidence suggests the presence of earlier ephemeral ice sheets. Sediment cores from Ocean Drilling Program (ODP) Legs 119 and 188 in Prydz Bay provide an archive of conditions in a major drainage system of East Antarctica. We study biomarker and microfossil evidence to discern how the vegetation and climate shifted between 36-33 Ma. Pollen were dominated by reworked Permian Glossopterid gymnosperms; however, penecontemporaneous Eocene pollen assemblages indicate that vegetation such as moss, ferns, southern beech and podocarp trees grew in the region and survived the glacial advances suggesting some non-glaciated land. At the EOT, brGDGT soil biomarkers indicate abrupt cooling from 13-8C and soil pH increases from 6.0 to 6.7, suggesting drying. The biomarker proxies record cooling in under 50 ka, compared to the gradual trend detected by weathering proxies. Plant wax dD and d13C show further evidence for drying with shifts of 20 per mil and 1.1 per mil respectively across the EOT. Although the terrestrial soil biomarker influx mostly precludes use of TEX86, a few determinations find sea surface temperatures of 12C in the late Eocene cooling to 8C at the EOT. Marine productivity undergoes a sustained increase after the glacial advance, whether promoted by glacial nutrient flux and/or enhanced overturning circulation. Between the two glacial surge events of the Priabonian Oxygen Maximum (PrOM) at 37.3 Ma and the EOT at 33.7 Ma, we observe three warm events at 35.8, 34.9 and 34.7 Ma with a rise in temperature of 2-5C and increases in penecontemporaneous pollen and enhanced marine productivity, capturing the last flickers of Antarctic warmth before almost complete glaciation at the EOT.