巴丹吉林沙漠南缘高台盐湖记录的中晚全新世气候变化

Mid-to-Late Holocene climate changes on the southern margin of the Badain Jaran Desert: Evidence from the Gaotai Lake sediments

  • 摘要: 位于季风边缘区和受西风环流显著影响的巴丹吉林沙漠南缘的高台盐湖提供了中晚全新世亚洲干旱区气候变化的可靠记录。在OSL测年的基础上,通过对高台盐湖剖面CaCO3含量、色度(L*、a*、b*)、粒度端元组分(EM)等环境代用指标的综合分析,重建了我国西北地区中晚全新世的气候变化。结果表明,中晚全新世高台盐湖地区气候变化经历了4个阶段:约7.1~5.3 ka,代表河流作用的EM2占主导,为浅湖/滨湖相沉积环境,气候相对干旱;5.3~1.2 ka期间,代表悬移作用的EM1占主导,指示深湖相沉积环境,CaCO3含量和a*和b*指示流域降水增多,地表侵蚀加强,近源物质输入较多,为中晚全新世以来的最湿润期;1.2~0.2 ka期间,EM2指示沉积环境转为滨湖/浅湖相沉积,气候变干;0.2 ka以来,气候进一步变干,湖泊消亡,演变为现代沙丘堆积。区域古气候替代记录的对比表明,高台地区中晚全新世以来演化过程与中亚干旱区湖泊记录具有一致性,气候变化主要受西风环流与高纬度北大西洋共同影响。

     

    Abstract: The Gaotai Lake is located on the southern margin of the Badain Jaran Desert. Under the influence of Asia monsoon and westerlies, there preserve reliable records of climatic changes for the Asia’s interior during the Mid-to-Late Holocene. Based on OSL dating and high-resolution multi-proxy records such as carbonate content, color, grain-size end-member (EM) modeling, it is inferred that the lake has experienced four distinct phases of climatic changes during the period from Mid-to-Late Holocene. Our results suggest that it used to be a shallow lake or nearshore environment during 7.1~5.3 ka, under a relatively dry climate condition. During the period of 5.3~1.2 ka, the lake was expanded and reached its highest level. Also, the records of carbonate content and a* and b* indices indicate that precipitation was increased and erosion intensified, representing the wettest period during the time of Mid-to-Late Holocene. In the period of 1.2~0.2 ka, the region changed back to a shallow lake or nearhore environment, and the climate turned to dry again. After 0.2 ka, the lake disappeared and the place is predominated by modern sand dunes under a drier climate. Regional proxy records show that the evolution of the Gaotai Lake is consistent and comparable with the lake records in arid Central Asia, where the climate is mainly affected by the westerlies and the high-latitude North Atlantic Ocean.

     

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