Pleistocene North Atlantic Deep Water Production; A Southern Hemisphere Perspective

Faunal counts and stable isotopes of planktonic foraminifera are used to identify glacial-interglacial and millennial scale change in Pleistocene Atlantic interhemispheric transport. The sampling site, ODP Site 1085, has a sedimentation rate of approximately 5 cm/k.y. Samples were taken every 2 cm throughout the sections of the core representing the last 200 k.y., giving the site a resolution of approximately 500 years, high enough to observe glacial-interglacial variation, Dansgaard/Oeschger temperature cycles, and Heinrich events, within the Nyquist frequency. Globigerina bulloides, found in cold, nutrient-rich water, is used as a proxy for upwelling (Girardeau 1992). At Site 1085, G. bulloides peaks both during glacial and interglacial periods. The interglacial peaks covary with peaks of terrigenous sediment greater than 10 microns, an indicator of aeolian transport (Stuut et al. 2002), indicating a link between upwelling and wind strength at that time. The glacial peaks broadly correlate to a low C/N ratio, indicating a probable marine cause for the upwelling, such as an enhanced Benguela Current. Additionally, there is higher-frequency (sub-Milankovitch) variability through both the glacial and interglacial periods.