VARIATIONS IN PLANKTONIC FORAMINIFERA ASSEMBLAGES ACROSS THE LAST DEGLACIATION: A HIGH-RESOLUTION EXAMINATION OF A NORTH ATLANTIC DEEP-SEA SEDIMENT CORE

Analysis of marine proxies have shown that the deep-ocean circulation system during the last glacial was significantly different than today. Furthermore, these changes have been observed during the abrupt climate changes that punctuated the last deglacial interval, like Heinrich-1 (H1), the Younger Dryas (YD), the Bølling-Allerød (BA). The North Atlantic Ocean is a critical area of deep-water formation, therefore understanding the perturbations to the surface and deep-water systems in this area is critical to understanding the mechanisms that control these abrupt climate changes.

Core 15JPC (2230 m), taken from the Eirik Drift, was selected for this study because it contains an expanded section (> 2 m) of the last deglaciation and has good age control with 10 AMS ¹⁴C dates. Geochemical and sedimentological records, including benthic and planktonic d¹⁸O and d¹³C records, ice-rafted detritus counts, sedimentation rates, and percent coarse fraction records have already been generated for this core. This study conducted downcore planktonic foraminiferal species counts to further evaluate the rapid climate and water mass changes from the LGM to today, as well as during the rapid climatic events.

Research is ongoing but preliminary results show the expected trends with cold-water species like Neogloboquadrina pachyderma (sinistral) dominating the record, and warm-water species like Neogloboquadrina pachyderma (dextral) and Globigerina bulloides peaking during warmer events. Abundances remain static in all species at this site through the LGM and H1 and show changes to warmer waters during the BA. N. pachyderma (s) values peak, while all warm-water species decrease during the YD before abundances in all species return to LGM like values at the start of the Holocene. Interestingly, changes in surface and intermediate waters are only recorded during the YD at this site despite the fact that surface water processes are often invoked for the observed reductions in deep-water production during the YD and H1 event. This could indicate that the proposed surface water processes were significantly different during the YD and the H1 event, or that Core 15JPC was located near the source of these influxes during the YD and not during H1. Further work is needed to investigate these trends further.