A Rb/Sr record of catchment weathering response to Holocene climate change in Inner Mongolia

Authors

  • Zhangdong Jin,

    Corresponding author
    1. Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710054, China
    2. Nanjing Institute of Geography & Limnology, Chinese Academy of Sciences, Nanjing, 210008, China
    3. Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK
    • *Correspondence to: Z. Jin, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710054, China.
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  • Junji Cao,

    1. Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710054, China
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  • Jinglu Wu,

    1. Nanjing Institute of Geography & Limnology, Chinese Academy of Sciences, Nanjing, 210008, China
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  • Sumin Wang

    1. Nanjing Institute of Geography & Limnology, Chinese Academy of Sciences, Nanjing, 210008, China
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Abstract

Variation in the rubidium to strontium (Rb/Sr) ratio of the loess–palaeosol sequences has been proposed to reflect the degree of pedogenesis and weathering in the northwestern region of China. To characterize the Rb/Sr ratio of the dissolved loads of a single catchment, we analysed a 12·08 m sediment core from Daihai Lake in Inner Mongolia, north China. Dating control was provided by 210Pb, 137Cs and AMS-14C. Sequential extraction experiments were conducted to investigate the concentrations of Rb and Sr on various chemical fractions in the lake sediments. Down-core variation in the Rb/Sr ratios provides a record of Holocene weathering history. From 9 to 3·5 ka bp, accelerated chemical weathering was experienced throughout the Daihai catchment under mainly warm and humid conditions, and this reached a maximum at c. 5 ka bp. However, weathering was reduced between c. 8·25 and 7·90 ka bp, which may reflect the global 8·2 ka cooling event. After c. 2·5 ka bp, increased Rb/Sr ratios with higher frequency of fluctuations indicate reduced weathering within the Daihai catchment. The highest Rb/Sr ratios in the Little Ice Age lake sediments indicate the weakest phase of Holocene chemical weathering, resulting from a marked reduction in Sr flux into the basin. The Rb/Sr record also shows an enhancement of chemical weathering under today's climate, but its intensity is less than that of the Medieval Warm Period. Increased Rb/Sr in lake sediment corresponding to reduced catchment weathering is in striking contrast to Rb/Sr decrease in the glacial loess layers in the loess–palaeosol sequence. Copyright © 2005 John Wiley & Sons, Ltd.

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