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Diao Guiyi; Wen Qizhong(Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences, Guangzhou 510640)  
The contents of CaCO_3, Fe_2O_3, FeO and free Fe_2O_3 in the sediments of the Weinan Loess Section have been analyzed in order to investigate the geochemical feature of different layers and to explore paleoclimate change during formation of the section The results show that the contents of CaCO_3 and the ratios of Fe_2O_3/FeO (oxidation index of iron) may be taken as substitute indexes for precipitation and temperature changes during strata formation, respectively. And the degree of pedogenesis may be reflected by the ratio variation of free Fe_2O_3/FeO (free index of iron). Based on the distribution of CaCO_3 contents and the variation of ratio Fe_2O_3/FeO and free Fe_2O_3/Fe_2O_3 in the section, the paleoclimate since 142ka B. P. may be divided into six stages in this region: in the first stage (about 142-135ka B. P.), the paleoclimate was characterized by a more humid and slight warm climate; in the second stage (abuot 135-73ka B. P.), by a humid and warm climate; in the third stage (abuot 73-52ka B. P.), by a dry and cold climate; in the fourth stage (about 52 22ka B. P.), by a cool and slight humid climate with a stable temperature and larger variation of precipitation than that in other stages; in the fifth stage (about 22-11ka B. P.), by a very cold and dry climate and in the sixth stage (about 11ka B. P.-present), the climate was relatively humid and warm. The precipitation was suddenly changed when the cold stage converted to warm one and it was gradually changed when the warm stage converted to a cold one. The temperature was always gradually changed at both conversions.
【Fund】: 国家自然科学基金
【CateGory Index】: P532
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