Rb and Sr Geochemical Characterization of the Chinese Loess Stratigraphy and Its Implications for Palaeomonsoon Climate
Rb and Sr Geochemical Characterization of the Chinese Loess Stratigraphy and Its Implications for Palaeomonsoon Climate
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DOI：
10.1111/j.1755-6724.2000.tb00462.x
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发表时间：
2000-06
期刊：
影响因子：
--
通讯作者：
Chen Jun.;Yongjin Wang;Chengjin Yang;Lianwen Liu;Junfeng Ji;Lu Huayu
中科院分区：
文献类型：
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作者：
Chen Jun.;Yongjin Wang;Chengjin Yang;Lianwen Liu;Junfeng Ji;Lu Huayu
研究了洛川剖面黄土和古土壤样品中Rb和Sr的含量和分布特征。结果表明，Rb主要富集在小于2 μm的粒级中，仅存在于残渣相中; Sr主要分布在砂和粉砂粒级中，存在于残渣相和碳酸盐相中。因此，黄土和古土壤中Rb和Sr含量的变化不仅与冬季风强度所决定的降尘成分密切相关，而且与夏季风引起的成壤强度密切相关。这表明中国黄土序列中Rb/Sr比值的变化代表了东亚夏季风和冬季风气候在轨道时间尺度上的周期性变化。Sr浓度沿着序列的变化与过去2.5 Ma深海沉积物的氧同位素记录具有很高的相似性，而Rb浓度的变化则与同一剖面的重复样品的磁化率记录具有很好的一致性。这表明：（1）高纬冰量是东亚季风变化的主要原因;（2）中国黄土序列磁化率信号主要取决于成土作用。
Concentrations and distributions of Rb and Sr in loess and palaeosol samples from the Luochuan profile have been studied, in grain‐size fractions and chemical forms. Results show that Rb is quite rich in the fraction of less than 2 μm, and exits only in the residual phase, while Sr is distributed in sand and silt fractions, occurring in the residual and carbonate phases. Therefore, variations of the concentrations of Rb and Sr in loess and palaeosols are closely related not only to dustfall compositions depending on winter monsoon wind strength but also to summer monsoon‐induced pedogenic intensity. This indicates that variations of Rb/Sr ratio in Chinese loess sequences represent cyclic alternations of East Asian summer and winter monsoon climates on the orbital time‐scale. Variations in Sr concentrations along the sequence bear a high similarity to the oxygen isotope record of the deep sea sediments over the past 2.5 Ma, whereas variations in Rb concentrations are in good agreement with the record of magnetic susceptibility determined with the duplicated samples from the same profile. This suggests that (1) the high‐latitude ice volume is responsible for East Asian monsoon variations and (2) the signal of magnetic susceptibility depends dominantly on pedogenesis in Chinese loess sequences.