Journal
MARINE GEOLOGY
Volume 256, Issue 1-4, Pages 30-35Publisher
ELSEVIER
DOI: 10.1016/j.margeo.2008.09.010
Keywords
Heinrich events; oxygen isotopes; detrital carbonate
Categories
Funding
- United States Science Support Program
- National Environmental Research Council [NE/G001448/1]
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We report oxygen and carbon isotope results of detrital carbonate grains from Heinrich layers at three sites in the North Atlantic located along a transect from the Labrador Sea to the eastern North Atlantic. Oxygen isotopic values of individual detrital carbonate grains from six Heinrich layers at all sites average -5.6 parts per thousand +/- 1.5 parts per thousand (1 sigma: n=166), reflecting values of dolomitic limestone derived from source areas in northeastern Canada. The delta O-18 of bulk carbonate at Integrated Ocean Drilling Program (IODP) Site U1308 (re-occupation of Deep Sea Drilling Project (DSDP) Site 609) in the eastern North Atlantic records the proportion of detrital to biogenic carbonate and delta O-18 decreases to -5 parts per thousand during Heinrich (H) events 1, 2,4 and 5 relative to a background value of similar to 1 to 2 parts per thousand for biogenic carbonate. Bulk delta O-18 also decreases during H3 and H6 but only attains values of -1 parts per thousand, indicating either a greater proportion of biogenic-to-detrital carbonate or a different source. Because the delta O-18 of detrital carbonate is similar to 9 parts per thousand lower than foraminifer carbonate, any fine-grained detrital carbonate not removed from the inner test chambers will lower foraminifer delta O-18. We conclude bulk carbonate delta O-18 is a sensitive proxy for detrital carbonate and may be useful for identifying Heinrich layers in cores within and near the margins of the North Atlantic ice-rafted detritus (IRD) belt. (C) 2008 Elsevier B.V. All rights reserved.
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