| 内蒙古达里湖沉积记录的中晚全新世干旱事件 |
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| 引用本文： | 范佳伟,肖举乐,温锐林,张生瑞,黄云.内蒙古达里湖沉积记录的中晚全新世干旱事件[J].第四纪研究,2019(3):701-716. |
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| 作者姓名： | 范佳伟 肖举乐 温锐林 张生瑞 黄云 |
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| 作者单位： | 中国科学院地质与地球物理研究所;中国科学院地球科学研究院;中国地震局地质研究所;中国科学院大学地球与行星科学学院;河北师范大学资源与环境科学学院 |
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| 基金项目： | 国家重点基础研究发展计划项目(批准号:2017YFA0603400);中国科学院(B类)战略性先导科技专项项目(批准号:XDB26020203);国家自然科学基金项目(批准号:41130101、41702179和41672166);中国博士后基金项目(批准号:2018T110138和2017M610111)共同资助. |
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| 摘 要： | 最近20年位于东亚夏季风北部边缘的我国北方半干旱区遭遇更为频繁、更为严重的干旱事件。然而,有关该区域过去不同时间尺度气候干旱事件的特征及机制仍知之甚少。文章详细分析了内蒙古中东部达里湖DL04岩芯上部6.5 m沉积物中< 38 μm碳酸盐的Ca和Mg含量、δ^18O和δ^13C值以及全样有机质TOC和TN含量、TOC/TN(C/N)比值,基于高精度的AMS^14C年代标尺,恢复了最近6000年(日历年)湖区的水文、气候变化详细过程。结果表明:达里湖< 38 μm碳酸盐主要为湖泊水体沉淀的内生方解石,其Ca和Mg含量、δ^18O和δ^13C值增大反映湖水蒸发量超过补给水量,进而指示湖区干旱事件。TOC和TN含量减少以及C/N比值减小总体反映地表径流减弱引起的陆生有机质入湖减少以及湖泊初始生产率下降。达里湖沉积内生碳酸盐和有机质地球化学数据表明,在6000~5300 cal.a B.P.、3200~2800 cal.a B.P.、1650~1150 cal.a B.P.和650~300 cal.a B.P.,流域地表径流显著减弱、湖面显著降低、湖泊生产率显著下降、湖区气候显著变干、东亚夏季风显著减弱。最近6000年东亚夏季风显著减弱事件在定年误差范围内与北大西洋冰漂碎屑事件一致,而与热带西太平洋海表温度变化和太阳活动变化相关性较差,表明千、百年尺度东亚夏季风突变主要受控于北半球高纬气候变冷。
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| 关 键 词： | 达里湖 地球化学 水文 气候 东亚夏季风 最近6000年 |
Middle to Late Holocene drought events recorded by the sediments from Dali Lake,Inner Mongolia |
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| Fan Jiawei,Xiao Jule,Wen Ruilin,Zhang Shengrui,Huang Yun.Middle to Late Holocene drought events recorded by the sediments from Dali Lake,Inner Mongolia[J].Quaternary Sciences,2019(3):701-716. |
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| Authors: | Fan Jiawei Xiao Jule Wen Ruilin Zhang Shengrui Huang Yun |
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| Institution: | (Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029;Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029;Institute of Geology, China Earthquake Administration, Beijing 100029;College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049;College of Resources and Environmental Sciences, Hebei Normal University, Shijiazhuang 050024, Hebei) |
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| Abstract: | The semi-arid areas in Northern China at the northern margin of the East Asian summer monsoon(EASM) have experienced an increased frequency and severity of drought in recent two decades. However, little is known about the characteristics and mechanisms of past drought events in this region on different timescales. In this study, the upper 6.5 m of a sediment core(DL04)(43°15.68'N, 116°36.26'E) recovered from Dali Lake(43°13'~43°23'N, 116°29'~116°45'E) in central-eastern Inner Mongolia is analyzed for Ca and Mg concentrations,δ^18O and δ^13C values of < 38-μm carbonates;and for total organic carbon(TOC) and total nitrogen(TN) concentrations and TOC/TN(C/N) ratio of organic matter in bulk sediments. Based on the precise AMS^14C dates, these proxy data document a detailed process of changes in the hydrology and climate in the region during the last 6000 cal.a. The results indicate that the < 38-μm carbonates in the Dali Lake sediments are predominated by endogenic calcites precipitated within the water body of the lake. Increases in the Ca and Mg concentrations,δ^18O and δ^13C values are interpreted as the intensive evaporative losses overwhelming the water input to the lake and thus the drought events in the region. Meanwhile, decreases in the TOC and TN concentrations and C/N ratios generally reflect decreases in the terrestrial organic matter input to the lake and declines in the primary productivity of the lake induced by weakened surface runoffs. The geochemical data of endogenic carbonates and organic matter from the Dali Lake sediments suggest that significant weakening in the surface runoffs, decreases in the lake level and phytoplankton productivity and drying in the regional climate, and thus significantly weakening in the EASM intensity occurred at the intervals of 6000~5300 cal.a B. P., 3200~2800 cal.a B. P., 1650~1150 cal.a B. P. and 650~300 cal.a B. P. Large declines in the EASM intensity during the last 6000 cal.a correspond, within age uncertainties, to the occurrences of ice rafted debris in the North Atlantic, but not coincide well with the changes in the sea surface temperature of the western tropical Pacific and in the solar activity, indicating that millennial and centennial abrupt changes in the EASM intensity are mainly triggered by climatic cooling occurring in the northern high latitudes. |
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| Keywords: | Dali Lake geochemistry hydrology climate East Asian summer monsoon last 6000 cal a |
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