中文摘要：

选择黄土高原南部的XJN,XMC和JYC全新世剖面为研究对象。通过对地层中Ca,Ba,Rb和Sr元素分布的研究,发现Ba/Sr和Rb/Sr比值在不同地层中含量差异十分明显,并与成土作用强度显著正相关,可作为良好的气候替代指标;表生环境中Rb和Ba较稳定,Sr和Ca元素十分活跃,易于迁移,其中Ca的迁移能力高于Sr元素;从XJN→XMC→JYC剖面,Rb和Ba元素含量增加,而Sr和Ca元素含量降低,这与区域环境差异有关;全新世中期暖湿的亚热带气候主要出现关中盆地地区,六盘山以西则是暖温带气候。

英文摘要：

The Holocene loess-soil sequences are of great values in the study of paleoclimate. Loess and soil samples from three Holocene sites at Xujianan （XJN） , Xiamengcun （ XMC ） , and Jiangyangcun （ JYC ） in the southern Loess Plateau were analyzed for their Ca, Ba, Rb, and Sr concentrations. Experimental results show that Ca, Ba, Rb, and Sr element concentrations and Ba/Sr and Rb/Sr ratios have obvious differentiation in palaeosol and loess layers, and an obvious differentiation of geochemical properties of the XJN, XMC, and JYC sites has been recognized. The Ba/Sr and Rb/Sr ratios of soil So gradually increase when soil type varies from the Eluvial Cinnamon soil of the JYC site to the Heilutu soil of the XJN site. These results indicate that the Ba/Sr and Rb/Sr ratios are very sensitive to climatic change and are thus good proxy indexes of climatic change during the Holocene. High value of Ba/Sr and Rb/Sr ratios indicates strong weathering, high precipitation and strong life activity, while low value indicates decreased weathering intensity, lower precipitation and increasing accumulation of aeolian dust. In comparison with Sr and Ca elements, under hypergene environments Rb and Ba elements are relatively stable and thus remain in palaeosol layers, while Sr and Ca are more active and easily leached out from palaeosol layers. Our results suggest that migration ability of Ca is higher than that of Sr. Statistic analyses suggest that there is a close relation between Ca, Ba, Rb, Sr element concentrations and grain size. The Ba and Rb elements tend to distribute in particle of less than 25μm in diameter, while the Ca and Sr elements tend to distribute in particle of more than 25 μm in diameter. Research results show that there exists an obvious positive correlation between Ba and Rb element contents and particle of less than 10μm in diameter, and an obvious positive correlation between Ca and Sr element contents and particle between 10 -50μm. The XJN site displays some differences from the XMC and JYC sit