Osmium isotope record of Late Pleistocene sediments@en

We report high temporal resolution osmium isotopes records of bulk sediment and sediment leachates from DSDP Site 480 (Gulf of California) over the last 30 ka; from ODP Site 849 (Eastern equatorial Pacific) from the last 200 ka and from ODP Site 1002C (Cariaco Basin) across the 9–17 ka time interval in order to critically evaluate claims of a global 10% shift in the 187Os/188Os of seawater from glacial to interglacial intervals. We use organic-rich continental margin sites and carbonate-rich pelagic sites to isolate the temporal variations of the osmium seawater isotopic composition. Our results reveal that variations in 187Os/188Os fail to correlate with global changes in temperature across glacials/interglacials cycles as previously claimed. Instead, these results indicate differences of a few percent in the measured 187Os/188Os between each oceanic basin. We argue that these differences strongly suggest that seawater is not well homogenized with respect to its Os isotope composition.本研究报道了过去30 ka以来加利福尼亚湾深海钻探计划（Deep Sea Drilling Project, DSDP）480站位全沉积物与沉积物浸提物的高时间分辨率锇同位素（osmium isotopes）记录；同时纳入了过去200 ka以来东赤道太平洋大洋钻探计划（Ocean Drilling Program, ODP）849站位的相关数据，以及9~17 ka时间区间内卡里亚科盆地ODP 1002C站位的记录，以此严格评估关于冰期至间冰期时段海水187Os/188Os比值发生全球10%偏移的论断。本研究选取富有机质陆缘站位与富碳酸盐远洋站位，以解析海水锇同位素组成的时间变化特征。研究结果显示，187Os/188Os比值的变化与此前所提出的冰期-间冰期旋回全球温度变化并无关联。与之相反，本结果表明不同大洋盆地间测得的187Os/188Os比值存在百分之几的差异。据此我们认为，上述差异清晰表明海水的锇同位素组成并未达到完全均一化的状态。