| 柴达木盆地察尔汗湖相沉积物的粒度分布模式及其环境意义 |
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| 引用本文： | 安福元,马海州,魏海成,樊启顺,韩文霞.柴达木盆地察尔汗湖相沉积物的粒度分布模式及其环境意义[J].干旱区地理,2013,36(2):212-220. |
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| 作者姓名： | 安福元 马海州 魏海成 樊启顺 韩文霞 |
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| 作者单位： | 1. 中国科学院青海盐湖所盐湖资源与化学重点实验室,青海西宁810008;中国科学院研究生院,北京100049
2. 中国科学院青海盐湖所盐湖资源与化学重点实验室,青海西宁,810008 |
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| 摘 要： | 对柴达木盆地察尔汗地区ISL1A孔的湖相沉积物样品进行了粒度分布特征分析，研究表明：（1）样品的粒度特征呈三峰模式，部分高盐阶段样品缺失第三峰，为双峰模式；（2）2～10 μm部分以湖成组份为主；10～70 μm和70～650 μm部分以风成组份为主；（3）<2 μm的组份可能与湖泊的生物化学成因有关。上述各组份与气候变化密切相关，且各自代表的环境意义也不同：<2 μm和2～10 μm部分反映了湖泊淡化-咸化程度和水量变化过程。10～70 μm部分可能在一定程度上反映了东亚冬季风的强度；70～650 μm部分反映了尘暴天气的程度。环境指标的对比分析很好地验证了ISL1A孔样品粒度各个组份划分的准确性，并可反演92.9 ka以来该地区的古气候演化过程。
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| 关 键 词： | 湖相沉积物 粒度分布模式 环境意义 柴达木盆地 察尔汗 |
| 收稿时间： | 2012-07-18; |
Grain-size distribution patterns of lacustrine sediments of Qarhan area and its environmental significance |
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| AN Fu-yuan,MA Hai-zhou,WEI Haicheng,FAN Qi-shun,Han Wen-xia.Grain-size distribution patterns of lacustrine sediments of Qarhan area and its environmental significance[J].Arid Land Geography,2013,36(2):212-220. |
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| Authors: | AN Fu-yuan MA Hai-zhou WEI Haicheng FAN Qi-shun Han Wen-xia |
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| Institution: | （1 Key Laboratory of Salt Lake Resources and Chemistry, Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining 810008, Qinghai，China; 2 Graduate University of Chinese Academy of Sciences，Beijing 100049，China） |
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| Abstract: | The Qarhan playa located in the eastern-central Qaidam Basin，surrounded by Gobi and yardang fields in actively folding sedimentary strata，has been become a lacustrine deposition center of the Tarim basin since the Quaternary. As a huge pitfall，the palaeolake traps a mass of aeolian deposits，so the sediments of this area are a mixed volume，which contains multiple components （such as lacustrine component，aeolian component，fluvial component and so on） and its grain-size frequency distribution curves show polymodal pattern. However，so far，these multiple components and their significance are still one of the fundamental enigmas. This study aims to distinguish the above multiple components and demonstrate the environmental significance of each component. Here a 102.13-meter-long lacustrine sediment core （labeled ISL1A） is presented obtained from the Qarhan playa. Through observing the grain-size frequency distribution curves for samples of ISL1A core，it is found that the grain-size distribution patterns of most lacustrine samples are trimodal，but part samples of hyperhaline phase are bimodal，absenting the third peaks. Based on grain-size parameter analysis as well as the method which is comparing the grain-size frequency distribution curves for samples of ISL1A core with that for several classic sediments，it is found that the curves of 2-10 μm fraction for this core are similar as that of stable lacustrine sediment，suggesting they are mainly lacustrine component; the curves of 10-70 μm and 70-650 μm fraction are similar as the that of loess and dust storm sediment，suggesting they are both mainly aeolian component; Grain-size distribution patterns of different evolution phases （salt-forming phase，semiarid phase and humid phase） show the fraction of less then 2 μm may relate to the origin of microorganismal chemistry，because the fraction disappears in hyperhaline phase but presents in semiarid and humid phase. In order to testify the above conclusion，the multi-proxies records are introduced （halite，calcite，Fe content，A/C value for pollen and F value for grain-size） and found that the respective component of grain-size all relates to the change-process of palaeoclimate. Moreover，different components indicate the different paleoclimate significances: the fractions of less than 2 μm and 2-10 μm reflect salinity of paleolake and the runoff intensity of catchment; 10-70 μm fraction probably indicates variation of the East Asian winter monsoon; 70-650 μm fraction indicates the intensity of dust storms of in the past. Finally，the multi-proxies records well testify our previous conclusion and can reconstruct the paleoclimate evolution course since 92.9 ka in the Qaidam Basin: 92.8-83.1 ka （MIS 5b），the climate was somewhat droughty; 83.1-71.0ka （MIS 5a），the climate became rather humid; 71.0-64.0ka （MIS 4），the climate was relatively dry; 64.0-47.1ka （MIS 3c），the palaeoclimate was very humid，the lake became freshwater-lake; 47.2-34.3 ka （MIS 3b），the climate became pretty dry，the palaeolake turned into a saline lake，and the East Asian Winter Monsoon （EAWM） was rather strong; 34.3-22.2 ka （MIS 3a），the climate got humid again; 22.2-14.1 ka （MIS 2），the palaeoclimate appeared very degradational，the lake went into the second salt period，and the EAWM was strengthen sharply; 14.1-9.0 ka （MIS 1），it went into post glacial and the climate began to improve. |
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| Keywords: | Lacustrine sediments Grain-size distribution pattern environmental significance Qaidam Basin Qarhan area |
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