NORTH ATLANTIC OCEAN CIRCULATION RESPONSE TO CLIMATE CHANGE AT EOCENE-OLIGOCENE TRANSITION, IODP SITE U1411, NEWFOUNDLAND RIDGE DRIFT COMPLEX
The main objectives of the grain-size analysis are to obtain data on (1) the ‘sortable silt’ (SS) fraction (10-63 µm) to generate a record of relative change in current velocity and (2) the abundance of lithogenic sand (>63 µm), which might relate to the occurrence of ice-rafted detritus. Preliminary data reveal a change across the EOT, from highly variable mean SS in the Eocene to a more restricted mean SS in the Oligocene. The data also show a long-term increase in mean grain size over the studied interval, which is most apparent in the measured range (1-63 µm). These results suggest a change in the DWBC at the EOT from a temporally variable current intensity to a relatively stable one, which may support hypotheses of EOT invigoration of ocean circulation. The abundance of lithogenic sand increases from negligible to measurable weight percentages across the EOT with a long-term increase through the Oligocene. More detailed examination of the grain-size distributions of the fine fraction, as well as comparisons to other proxies, will be helpful in deciphering the nature of DWBC changes and in informing our understanding of the evolution of ocean circulation during the EOT.