Evolution of seawater 87Sr86Sr over the last 400 ka: the absence of glacial/interglacial cycles
Evolution of seawater 87Sr86Sr over the last 400 ka: the absence of glacial/interglacial cycles
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过去 400ka 海水 87Sr86Sr 的演化：冰期/间冰期循环的缺失
DOI：
10.1016/0012-821x(94)90176-7
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发表时间：
1994
影响因子：
5.3
通讯作者：
N. Shackleton
中科院分区：
文献类型：
--
作者：
G. Henderson;D. J. Martel;R. O’nions;N. Shackleton
近年来已有研究报道了海水87 Sr - 86 Sr比值随冰期/间冰期气候变化的波动，但仍存在很大争议。为了研究这些潜在的波动，我们对来自印度洋和太平洋岩心的浮游有孔虫进行了高精度（13 ppm） 87 Sr 86 Sr测量。在岩心顶部和50 ka样品中，来自三种不同有孔虫物种的87sr - 86sr比值难以区分，表明成岩作用或污染引起的变化不会影响测量结果。太平洋和印度洋样品的平均87 Sr - 86 Sr比在三个区间（岩心顶部、50 ka和300-370 ka）也无法区分，表明海洋在Sr方面保持了良好的混合。此外，87 Sr - 86 Sr比不受样品预清洗变化的影响。Dia等人的研究中使用的太平洋岩心V28-238的测量结果并没有再现先前研究中看到的旋回，而且在统计上可以很好地解释为海水87 Sr - 86 Sr比值的线性增加。在之前的研究中，似乎是一种分析人工制品导致了这种循环。在Clemens等人的研究中使用的ODP站点758的两个关键岩心部分的测量结果，并没有再现先前研究中看到的最大位移，尽管这里报道的精度要高得多。Clemens等人的[2]数据中明显的周期性也被认为是由于未知的分析伪象。这里给出的48个测量值在统计上很好地符合Δ 87 Sr (ppm)= - 0.0613×年龄（ka）定义的直线。在13 ppm的精度水平上，没有发现海水87 Sr - 86 Sr比出现冰期/间冰期变化的证据。冰期/间冰期变化可能仍然存在，但这一数据将其最大振幅限制在6 - 9ppm，这相当于河流Sr通量的变化≈30%。
Abstract Fluctuations in the 87 Sr 86 Sr ratio of seawater accompanying glacial/interglacial climate changes have been reported in recent studies but remain highly controversial. To investigate these potential fluctuations we present very high precision (13 ppm) 87 Sr 86 Sr measurements on planktonic foraminifera from Indian Ocean and Pacific cores. 87 Sr 86 Sr ratios from three different foraminiferal species are indistinguishable from one another in both core-top and 50 ka samples, demonstrating that changes due to diagenesis or contamination do not influence the measurements. Average 87 Sr 86 Sr ratios for Pacific Ocean and Indian Ocean samples are also indistinguishable at three intervals (core-top, 50 ka and 300–370 ka), demonstrating that the oceans have remained well mixed with respect to Sr. Also, 87 Sr 86 Sr ratios are not affected by changes in the precleaning of samples. Measurements from Pacific core V28-238, that used in the study of Dia et al.[1], do not reproduce the cycles seen in the previous study and are statistically well explained by a linear increase in the seawater 87 Sr 86 Sr ratio. It seems likely that an analytical artefact caused the cycles in the previous study. Measurements from two key sections of core from ODP site 758, that used in the study of Clemens et al.[2], do not reproduce the largest shifts seen in the previous study, despite the considerably better precision reported here. The apparent cyclicity in the Clemens et al.[2] data is also suggested to be due to an unknown analytical artefact. The 48 measurements presented here are a statistically good fit to a straight line defined by Δ 87 Sr (ppm)=− 0.0613× age (ka). At the 13 ppm level of precision no evidence for a glacial/interglacial variation in the seawater 87 Sr 86 Sr ratio is seen. Glacial/interglacial variation may still exist but this data constraints its maximum amplitude to 6–9 ppm, which would correspond to changes in the riverine Sr flux of≈ 30%.