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A Late Glacial to Holocene Sediment Record of Ice-Rafted Detritus from Orphan Knoll, Northwest Atlantic Ocean
Anastopoulos, Kristen M. Anastopoulos, Kristen M. Cullen, James L. Cullen, James L.
Anastopoulos, Kristen M.
Anastopoulos, Kristen M.
Cullen, James L.
Cullen, James L.
Title
A Late Glacial to Holocene Sediment Record of Ice-Rafted Detritus from Orphan Knoll, Northwest Atlantic Ocean
Date
2021-05-01
Subject
Atlantic
Detrital
Heinrich Event
IRD
Sediment
Detrital
Heinrich Event
IRD
Sediment
Material type
Collections
Abstract
High-resolution sediment records from North Atlantic deep-sea sediments have been used to document millennial-scale abrupt climate oscillations during the last glacial cycle. A five-meter core (DY081-GVY002) was recovered from the Orphan Knoll, Northwest Atlantic Ocean during the RRS Discovery Cruise ICY LAB in 2017. Forty-closely spaced samples from the top 65cm (1-2 cm spacing) have been used to generate two proxies that record changes in the input of ice-rafted detritus (IRD): IRD/g, lithic grains >150µm per gram of sediment, %IRD ((number of lithic grains >150µm) / (number of lithic grains >150µm + number of planktic foraminifers >150µm)) x 100). Our record, which significantly improves the resolution previously presented by Gugliemli et al. (2020), reveals a series of abrupt increases in IRD input ranging from 4,000-7,200 lithic grains/g within a background of 3,000 or less lithic grains/g, at 5cm, 10cm, 25cm, 38cm and 44cm. The %IRD record reveals high values over the interval of 34cm-55cm that correspond to high IRD/g input which can be correlated to an interval of high Ca/Sr ratios, a proxy that has been previously used to indicate the input of detrital carbonates composed of dolomite and/or inorganic calcite (Hodell et al. 2008). We have preliminarily correlated this interval to Heinrich event 1 (H1), one of a series of abrupt increases in IRD input that occurred throughout the North Atlantic during the last glacial (MIS 4-2); (Heinrich 1988). Another high interval in the Ca/Sr ratio occurs at 12-15cm this corresponds to a peak in %IRD, we have preliminarily correlated this interval as Heinrich event 0 (H0). Our data suggests a closer relationship between %IRD and Ca/Sr proxies, whereas IRD/g is more easily influenced by other factors. The other peaks in IRD/g that also record low %IRD occur when Ca/Sr ratios are at lower background levels, suggesting the decoupling of these proxies for reasons we have not been able to explain yet.