(Appendix A) Oxygen and carbon isotope results of detrital carbonate grains of Heinrich layers from HU90-013-028 and IODP Sites 303-U1302/U1303/U1308 in the North Atlantic Ocean

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 ppm ± 1.5 ppm (1sigma; n = 166), reflecting values of dolomitic limestone derived from source areas in northeastern Canada. The d18O 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 d18O decreases to - 5 ppm during Heinrich (H) events 1, 2, 4 and 5 relative to a background value of ~ 1 to 2 ppm for biogenic carbonate. Bulk d18O also decreases during H3 and H6 but only attains values of - 1ppm, indicating either a greater proportion of biogenic-to-detrital carbonate or a different source. Because the d18O of detrital carbonate is ~ 9 ppm lower than foraminifer carbonate, any fine-grained detrital carbonate not removed from the inner test chambers will lower foraminifer d18O. We conclude bulk carbonate d18O 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.本研究报道了沿拉布拉多海（Labrador Sea）至北大西洋东部（eastern North Atlantic）断面分布的3个北大西洋站位的海因里希层（Heinrich layers）中碎屑碳酸盐颗粒（detrital carbonate grains）的氧、碳同位素测试结果。所有站位6个海因里希层中单个碎屑碳酸盐颗粒的氧同位素值平均值为-5.6‰±1.5‰（1σ；n=166），反映其源自加拿大东北部物源区的白云质灰岩（dolomitic limestone）。北大西洋东部站位综合大洋钻探计划（Integrated Ocean Drilling Program, IODP）U1308井位（为深海钻探计划（Deep Sea Drilling Project, DSDP）609井位的复钻站位）的整体碳酸盐（bulk carbonate）的δ¹⁸O值记录了碎屑碳酸盐与生物成因碳酸盐（biogenic carbonate）的占比；相较于生物成因碳酸盐~1~2‰的背景值，在海因里希事件（Heinrich events, H）1、2、4、5期间，δ¹⁸O值降至-5‰。在H3和H6事件期间，整体碳酸盐δ¹⁸O值同样出现下降，但仅降至-1‰，这表明要么生物成因碳酸盐相较于碎屑碳酸盐的占比更高，要么物源发生了变化。由于碎屑碳酸盐的δ¹⁸O值相较于有孔虫碳酸盐（foraminifer carbonate）低约9‰，若有细粒碎屑碳酸盐未从有孔虫壳室中去除，则会降低测得的有孔虫δ¹⁸O值。本研究认为，整体碳酸盐δ¹⁸O值是碎屑碳酸盐的灵敏代用指标，可用于识别北大西洋冰筏碎屑（ice-rafted detritus, IRD）带内部及其边缘附近岩芯中的海因里希层。