High Resolution Record Of Ice Rafted Detritus In Central North Atlantic Deep-Sea Sediment Core V30-100

Abstract

High resolution records from North Atlantic deep-sea sediments have been instrumental in documenting millennial scale climate fluctuations during Marine Isotope Stages (MIS) 4-1, including variations in concentrations of ice rafted detritus (IRD) related to massive iceberg discharges from Northern Hemisphere ice sheets. We have analyzed 149 closely spaced samples from the top 2 meters of North Atlantic piston core V30-100 (44°06.5’N, 32°30’W) and produced detailed records of %IRD (%lithics=(#lithic grains >150 microns)/(#lithic grains >150 microns + #planktic foraminifera >150 microns)*100), IRD per gram (lithic grains >150 microns per gram sediment), and planktic forams per gram (whole planktic foraminifers >150 microns per gram sediment). %IRD reveals 4 distinct intervals of >80% IRD coupled with consistently very low forams per gram at 40-48cm, 80-88cm, 137-149cm, and 179-184cm separated by long intervals of significantly lower IRD (<20%). The IRD per gram (lithics per gram) is consistently above 3000 lithics per gram during the intervals of high %IRD but show considerably more variability. %IRD and lithics per gram show a distinct lack of correlation at higher values. This is likely due to the influence of changes in planktic foram production affecting our proxies of IRD input. Upon analysis of our high-resolution IRD records with the low-resolution carbonate record from V30-100 as well as our detailed comparison to other IRD records from the Central North Atlantic (Hemming, 2003) suggests that the 4 intervals of high %IRD in V30-100 correspond to well documented Heinrich events that occurred in the North Atlantic during the last glacial interval (MIS 4-2). We have correlated the high IRD event centered around 180cm to H5, and the interval centered around 145cm to H4. The IRD events centered around 85cm and 45cm have been correlated to H2 and H1, respectively. If these correlations are correct, H3 has not been recorded in V30-100.