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高校地质学报 ›› 2023, Vol. 29 ›› Issue (2): 316-324.DOI: 10.16108/j.issn1006-7493.2021051

• 其他学科 • 上一篇    

近百年来二龙湾沉积物粒度端元分析及其环境意义

廖东霞,郭海婷,吴孟孟,潘少明*   

  1. 南京大学 地理与海洋科学学院,南京 210023
  • 出版日期:2023-04-20 发布日期:2023-04-20

End Member Model Analysis of Sediments Grain-size from Erlongwan Maar Lake and Corresponding Environmental Implication in the Past 100 Years

LIAO Dongxia,GUO Haiting,WU Mengmeng,PAN Shaoming*   

  1. School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China
  • Online:2023-04-20 Published:2023-04-20

摘要: 沉积物粒度蕴含着区域降水强度、湖泊水位波动、沉积物物源等古环境信息。文章以二龙湾2个沉积物岩芯为研究对象,利用GMX30P-A高纯Ge同轴探测器和英国Mastersize2000型激光粒度仪对样品进行137Cs比活度和粒度测试,运用参数化EMA端元模型对沉积物样品的粒度数据集进行端元分解,探讨二龙湾近百年来沉积物质来源和沉积环境特征。二龙湾沉积物主要为水成沉积,含少量风成沉积,EM1和EM2指示水动力较弱的封闭湖泊沉积环境,EM3指示强地表径流搬运过程。坡面径流挟带的流域碎屑颗粒物是沉积物的主要物源,高空西风携带的远源粘粒级颗粒和中尺度区域风搬运的近源粉尘物质对沉积物有一定的贡献。近百年来二龙湾经历封闭湖泊沉积过程,沉积环境较为稳定,湖心沉积速率小于近岸沉积速率。1963年后沉积物中细颗粒物质含量增加,粗颗粒物质占比大幅下降,表明吉林龙湾国家级然保护区的建成对流域的水土保持有重要作用。

关键词: 二龙湾, 粒度端元模型, 沉积环境

Abstract:

Sediment grain size contains paleo-environmental information such as regional precipitation intensity, water level fluctuation and sediment provenance. The end-member modeling analysis can extract the end members representing different sedimentary dynamic processes. We collected two sediment cores from the center and the shore of the Erlongwan Maar Lake. 137Cs activities were measured by Coaxial High Purity Germanium Detector GMX30P-A Series, particle size was measured by the Malvern Mastersizer 2000. The parametric EMA modeling was used to analyze the grain size data of sediment cores in Erlongwan Maar Lake. Based on the results, we analyzed the sediment source and the sedimentary environment of Erlongwan Maar Lake in the past 100 years. The results indicate that the parametric EMA modeling has recognized three end members. The sediments in
Erlongwan Maar Lake are thought to be aqueous mainly, and the eolian deposits are relatively less. From EM1 to EM3, the mode
particle size increases successively. EM1 represents eolian deposits and fine-grained materials carried into the lake by flowing water. EM2 comes from the erosion of debris in the basin by surface runoff, which is the major component of sediments. EM1 and EM2 indicate a closed lake sedimentary environment with weak hydrodynamics, and EM3 indicates a process of strong surface runoff transport. The detrital material derived from continent is the main source of sediments. The distant clayey particles carried by the upper westerly wind and the near dust particles carried by meso-scale regional wind also contribute to the sediments. The sedimentary environment is relatively stable during recent 100 years. The sedimentation rate of the lake core is lower than that of the lakeshore. After 1963, the content of fine-grained materials increased, while the proportion of coarse-grained components decreased. This means the improvement of ecological environmental and the decrease of surface materials loss, which indicates that the establishment of Jilin Longwan National Nature Reserve plays an important role in soil and water conservation. 

Key words: Erlongwan Maar Lake, end member model, sedimentary environment

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