Distribution of Rb and Sr in the Luochuan loess- paleosol sequence of China during the last 800 ka |
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| Authors: | Jun Chen Zhisheng An Yongjin Wang Junfeng Ji Yang Chen Huayu Lu |
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| Institution: | (1) Department of Earth Sciences, State Key Laboratory of Mineral Deposit Research, Nanjing University, 210093 Nanjing, China;(2) State Key Laboratory of Loess and Quaternary Geology, Chinese Academy of Sciences, 710054 Xi’an, China;(3) Department of Geography, Nanjing Normal University, 210097 Nanjing, China |
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| Abstract: | The concentrations of Rb and Sr, and magnetic susceptibility in loess and paleosol samples from the Luochum profile have been
measured. The loess units deposited in different geological periods display a very similar pattern of Rb and Sr distribution
while paleosol units exhibit a dramatic increase in the Rb/Sr ratio, ranging from 20% to 120% in increase amplitude. Owing
to different geochemical behavior of the two elements, Rb appears to be immobile while Sr appears to be mobile in the processes
of weathering and pedogenesis. So variations of the Rb/Sr ratio in the loess-paleosol sequences could reflect intensities
of weathering and pedogenesis, thus recording the relative wind strength of the East Asian summer monsoon circulation. This
could be supported by the high degree of cornlation between the Rb/Sr ratio and the magnetic susceptibility. A continuous
record of the Rb/Sr ratio in the Luochuan profile over the last 800 ka bears a striking resemblance to the δ18 O curve of the deep sea sediments and is in accordance with the SPECMAP chronology. Such similarity between the terrestrial
and the deep sea records suggests that variability in global ice volume is a primary dynamic factor controlling long-term
changes of the East Asian summer monsoon intensity.
Project supported by the National Natural Science Foundation of China (Grant No. 49725307). |
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| Keywords: | loess Rb/Sr ratio paleomonsoon variation chemical weathering |
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