Towards an orbital time scale for chinese loess deposits
Towards an orbital time scale for chinese loess deposits
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DOI：
10.1016/0277-3791(94)90124-4
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发表时间：
1994
影响因子：
4
通讯作者：
Z. Ding;Z. Yu;N. Rutter;Tung-sheng Liu
中科院分区：
文献类型：
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作者：
Z. Ding;Z. Yu;N. Rutter;Tung-sheng Liu
本文以宝鸡黄土-土壤序列为研究对象，分析了每10 cm的粒度特征。结果表明，黄土粒度变化对黄土-土壤交替非常敏感，黄土单元比土壤单元粗得多。黄土颗粒的这种变化被解释为西伯利亚冬季季风强度的冰川-间冰期循环变化的结果。因此，粒度记录被用作冬季风环流的代理指标，并与Berger和Loutre（1991）最近计算的主要磁反转控制下的轨道记录相一致。调谐与深海沉积物中δ 18 O信号的任何相关性无关。由此得到的粒度时间尺度受到严格的约束，这表明：（1）从轨道时间尺度上的粒度数据中过滤出的磁率和岁差分量与理论轨道记录非常吻合，（2）由粒度时间尺度估算的主要磁反转年龄与KAr年龄吻合较好;（3）在整个0- 2.5Ma期间，宝鸡粒度时间序列与轨道频率带的轨道变化具有密切的相关性;（4）在轨道时间尺度上的粒度记录与轨道调谐的DSDP Site 607和ODP Site 677 δ 18 O记录非常相似。粒度记录随时间变化的特征表明，有两个主要的转变，在长期的季风周期，一个发生在约0.8 Ma BP和其他约1.7 Ma BP的主导周期。
In this study, we analyzed the grain size of the Baoji loess-soil sequence at 10 cm intervals. Results show that grain size variations are very sensitive to loess-soil alternations, with loess units being much coarser than soils. Such a change in loess-soil grains is interpreted as the result of the glacial-interglacial cyclic variations in the intensity of the winter monsoon winds out of Siberia. The grain size record is thus employed as a proxy indicator of the winter monsoon circulation and tuned to the orbital records calculated recently by Berger and Loutre (1991) under the control of major magnetic reversals. The tuning is independent of any correlation with δ 18 O signals in the deep-sea sediments. The resulting grain size time scale is tightly constrained, as suggested by the following facts:(1) the filtered obliquity and precession components from the grain size data on the orbital time scale closely match the theoretical orbital records;(2) ages of the major magnetic reversals estimated from the grain size time scale are in good agreement with the K Ar-dated ages;(3) there is close coherence between the Baoji grain size time series and the orbital variations at the orbital frequency bands over the entire 0–2.5 Ma period; and (4) the grain size record on the orbital time scale shows a close similarity to the orbitally-tuned DSDP Site 607 and ODP Site 677 δ 18 O records. Examination of time-dependent characteristics of the grain size record suggests that there are two major shifts of dominant periodicities in the long-term monsoonal cycles, one occurring at about 0.8 Ma BP and the other around 1.7 Ma BP.