(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至北大西洋东部断面分布的3个北大西洋站位的海因里希层（Heinrich layers）碎屑碳酸盐颗粒的氧、碳同位素测试结果。所有站位6个海因里希层的单个碎屑碳酸盐颗粒的氧同位素值平均为-5.6‰±1.5‰（1σ；n=166），其数值对应源自加拿大东北部物源区的白云质灰岩的同位素特征。位于北大西洋东部的综合大洋钻探计划（Integrated Ocean Drilling Program, IODP）U1308站位（为深海钻探计划（Deep Sea Drilling Project, DSDP）609站位的复钻站位）的全岩碳酸盐δ¹⁸O记录了碎屑碳酸盐与生物成因碳酸盐的占比情况：相较于生物成因碳酸盐约1~2‰的背景值，海因里希（Heinrich，简称H）事件1、2、4、5期间的δ¹⁸O降至-5‰。H3与H6事件期间，全岩δ¹⁸O同样出现下降，但仅降至-1‰，这提示要么生物成因碳酸盐相较于碎屑碳酸盐的占比更高，要么物源存在差异。由于碎屑碳酸盐的δ¹⁸O较有孔虫碳酸盐低约9‰，若细粒碎屑碳酸盐未被清除出有孔虫壳体的内腔，则会导致测得的有孔虫δ¹⁸O值偏低。本研究得出结论：全岩碳酸盐δ¹⁸O是反映碎屑碳酸盐含量的敏感代用指标，可用于识别北大西洋冰筏碎屑（ice-rafted detritus, IRD）带内部及邻近岩芯中的海因里希层。