Rb and Sr Geochemical Characterization of the Chinese Loess Stratigraphy and Its Implications for Palaeomonsoon Climate |
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作者姓名: | CHEN Jun |
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作者单位: | CHEN JunDepartment of Earth Sciences,Nanjing University,Nanjing 210093WANG Yongjin,Department of Geography,Nanjing Normal University,Nanjing 210097CHEN Yang,LIU Lianwen,JI Junfeng Department of Earth Sciences,Nanjing University,Nanjing 210093and LU Huayu Xi 'an State Key Laboratory of Loess and Quaternary Geology,Chinese Academy of Sciences,Xi 'an 710061 |
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基金项目: | 中国科学院资助项目,the Doctoral Foundation of the Ministry of Education of China,49725307,,, |
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摘 要: | 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 2μm, 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
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关 键 词: | Rb and Sr geochemical characterization Rb/Sr ratios loess sequence palaeomonsoon climate Loess Plateau |
Rb and Sr Geochemical Characterization of the Chinese Loess Stratigraphy and Its Implications for Palaeomonsoon Climate |
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Authors: | CHEN Jun |
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Institution: | CHEN JunDepartment of Earth Sciences,Nanjing University,Nanjing WANG Yongjin,Department of Geography,Nanjing Normal University,Nanjing CHEN Yang,LIU Lianwen,JI Junfeng Department of Earth Sciences,Nanjing University,Nanjing and LU Huayu Xi 'an State Key Laboratory of Loess and Quaternary Geology,Chinese Academy of Sciences,Xi 'an |
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Abstract: | 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 m m, 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. |
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Keywords: | Rb and Sr geochemical characterization Rb/Sr ratios loess sequence palaeomonsoon climate Loess Plateau |
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