Oxygen and carbon isotopes of detrital carbonate in North Atlantic Heinrich Events

• Published in: Marine Geology
• Main Authors: Hodell, David A., Curtis, Jason H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2008
• Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems; Canada; Labrador Sea; North Atlantic
• Online Access: http://eprints.esc.cam.ac.uk/2274/; http://eprints.esc.cam.ac.uk/2274/1/hodell.pdf; http://elsevier-apps.sciverse.com/GoogleMaps/index.jsp?doi=10.1016/j.margeo.2008.09.010; https://doi.org/10.1016/j.margeo.2008.09.010

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‰ ± 1.5‰ (1σ; n = 166), reflecting values of dolomitic limestone derived from source areas in northeastern Canada. The δ18O 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 δ18O decreases to − 5‰ during Heinrich (H) events 1, 2, 4 and 5 relative to a background value of ∼ 1 to 2‰ for biogenic carbonate. Bulk δ18O also decreases during H3 and H6 but only attains values of − 1‰, indicating either a greater proportion of biogenic-to-detrital carbonate or a different source. Because the δ18O of detrital carbonate is ∼ 9‰ lower than foraminifer carbonate, any fine-grained detrital carbonate not removed from the inner test chambers will lower foraminifer δ18O. We conclude bulk carbonate δ18O 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.