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Evidence for early (>= 12.7 Ma) eolian dust impact on river chemistry in the northeastern Tibetan Plateau
Ruan, XB (Ruan, Xiaobai)1,3,4; Yang, YB (Yang, Yibo)1,2; Galy, A (Galy, Albert)4; Fang, XM (Fang, Xiaomin)1,2,3; Jin, ZD (Jin, Zhangdong)5; Zhang, F (Zhang, Fei)5; Yang, RS (Yang, Rongsheng)1,3,4; Deng, L (Deng, Li)5; Meng, QQ (Meng, Qingquan)6,7; Ye, CC (Ye, Chengcheng)1; Zhang, WL (Zhang, Weilin)1,2

As one of the largest dust sources on the Earth's surface, dryland in Central Asia gives rise to thick eolian deposits over East Asia (e.g., the Chinese Loess Plateau, CLP) and significantly influences the regional hydrochemistry in the downwind drainage areas. However, the formation of thick eolian dust deposits requires not only climatic prerequisites for dust emission and transport but also climatic and topographic conditions favourable for deposition and accumulation. The scarcity of widespread eolian deposition around the CLP before 7-8 Ma hinders a full understanding of the processes and mechanisms of Central Asian aridification. The deposition of eolian dust also impacts the hydrogeochemistry of fluvial systems and the precipitation of authigenic phases in continental sedimentary systems could be an archive for studying eolian dust dynamics when pure eolian deposits are scarce. Here, we present the Ca-Mg-Sr concentrations and Sr-87/Sr-86 isotope compositions of bulk carbonates in a new fluvial sequence (12.7-4.8 Ma) of the Xining Basin. The Mg/Ca and Sr/Ca ratios of the carbonate describe a power law relationship with a power coefficient of 0.8, lower than the coefficient characteristic of prior calcite precipitation (PCP). An input of eolian dust with the dissolution of Mg-rich carbonate is likely responsible for the deviation from a pure PCP process. The bulk carbonates also show a general decrease of Sr-87/Sr-86 ratios from 12.7 to 4.8 Ma, with a transition around 8.6 Ma revealed by lower Sr/Mg ratios. The comparison of these proxies to a previously reported fluvial section (12.2-5.1 Ma) in the Linxia Basin, similar to 200 km to the southeast, shows that the Sr-87/Sr-86 ratios of the bulk carbonates and water-soluble salts in the Linxia Basin are around 0.7098, which is 0.0018 lower than those in the Xining Basin before 8.6 Ma, but shows a significant rise between 8.6 and 7.0 Ma. The two basins share the same range of carbonate Sr-87/Sr-86 ratios when sediments are younger than 7 Ma. For the last 7 Myrs, the evolution of the Sr-87/Sr-86 ratios in bulk carbonates of fluvial sediments and Pliocene-Quaternary eolian deposits found in the Xining Basin are similar to those in typical eolian red clays/loess-palaeosol sequences on the CLP. These results suggest a transition of the hydrochemical regime at 8.6 Ma in the Linxia Basin from a catchment only influenced by the weathering of its bedrock to one significantly impacted by eolian dust input. In the Xining Basin, the carbonate elemental and Sr-87/Sr-86 ratios are consistent with a hydrochemistry more impacted by the presence of the eolian dust. There, the dust input occurred earlier, at >= 12.7 Ma, though it has strengthened since 8.6 Ma. The eolian dust impact on fluvial systems in the Xining Basin was much earlier than in the Linxia Basin and also preceded the initial accumulation of widespread eolian red clays on the CLP (7-8 Ma), suggesting a temporally propagating and spatially stepwise expansion of eolian dust delivery across the Asian inland during the late Cenozoic. (C) 2019 Elsevier B.V. All rights reserved.

Subject AreaGeosciences
WOS IDWOS:000466251400008
Indexed BySCI
KeywordChinese Loess Plateau Xining Basin Phased Uplift Carbonate Evolution Deposits Calcites Pacific Monsoon Origin
WOS Research AreaGeochemistry & Geophysics
WOS SubjectGeochemistry & Geophysics
Cooperation Status国际
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Document Type期刊论文
Corresponding AuthorYang, YB (Yang, Yibo); Fang, XM (Fang, Xiaomin)
Affiliation1.Chinese Acad Sci, Inst Tibetan Plateau Res, Key Lab Continental Collis & Plateau Uplift, Beijing 100101, Peoples R China;
2.Chinese Acad Sci, CAS Ctr Excellence Tibetan Plateau Earth Sci, Beijing 100101, Peoples R China;
3.Univ Chinese Acad Sci, Beijing 100049, Peoples R China;
4.Univ Lorraine, CNRS, UMR7358, Ctr Rech Petrog & Geochim, F-54500 Vandoeuvre Les Nancy, France;
5.Chinese Acad Sci, Inst Earth Environm, State Key Lab Loess & Quaternary Geol, Xian 710075, Shaanxi, Peoples R China;
6.Lanzhou Univ, Sch Earth Sci, Lanzhou 730000, Gansu, Peoples R China;
7.Lanzhou Univ, Key Lab Western Chinas Mineral Resources Gansu Pr, Lanzhou 730000, Gansu, Peoples R China.
Recommended Citation
GB/T 7714
Ruan, XB ,Yang, YB ,Galy, A ,et al. Evidence for early (>= 12.7 Ma) eolian dust impact on river chemistry in the northeastern Tibetan Plateau[J]. EARTH AND PLANETARY SCIENCE LETTERS,2019,515(0):79-89.
APA Ruan, XB .,Yang, YB .,Galy, A .,Fang, XM .,Jin, ZD .,...&Zhang, WL .(2019).Evidence for early (>= 12.7 Ma) eolian dust impact on river chemistry in the northeastern Tibetan Plateau.EARTH AND PLANETARY SCIENCE LETTERS,515(0),79-89.
MLA Ruan, XB ,et al."Evidence for early (>= 12.7 Ma) eolian dust impact on river chemistry in the northeastern Tibetan Plateau".EARTH AND PLANETARY SCIENCE LETTERS 515.0(2019):79-89.
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