苏州地区硬粘土粒度和元素地球化学特征及其环境意义  

Characteristics of Grain Size,Element Geochemistry and Their Environmental Implications of Hard Clay from Suzhou Area,China

作　　者：玄晓娜 赵庆[1] 周立旻[1] 杨华玮 徐洪阳 任少芳[1] 郑祥民[1] 刘峰[1] 陈璞皎 

机构地区：[1]华东师范大学地理科学学院地理信息科学教育部重点实验室,上海200241

出　　处：《地球与环境》2017年第5期555-566,共12页Earth and Environment

基　　金：国家基础科学人才培养基金项目(J1310028);国家自然科学基金项目(41371032)

摘　　要：长江三角洲晚更新世硬质粘土地层对于认识该区域晚更新世环境变化、现代工程建设等均具有重要意义,而其成因尚存较大争议。本文通过对苏州地区葑亭大道钻孔硬粘土地层样品进行粒度与元素地球化学分析,探讨其成因与古环境指示意义。结果表明:(1)苏州地区硬粘土平均粒径为5.2~7.1Φ,以粉砂颗粒为主,中、细粉砂颗粒含量在65%以上,频率曲线呈双峰分布,粒度谱分布为正偏态,分选较差;(2)环境判别显示其为风成堆积物,与南京、镇江下蜀黄土分布特征相似;(3)元素分析显示,硬粘土出现不同程度Na、P元素亏损和Mn、Al元素富集,化学风化作用处于中等风化阶段;(4)硬粘土层的上段和下段在粒度和元素特征上有明显区别,下段粒度明显偏粗,风化程度相对较弱。Based on systematical analysis of grain size and element geochemistry of the hard clay samples from Suzhou Area,China,it is found that the hard clay consists essentially of silty grains of 4 to 63 μm in size,with an average grain diameter of 5.2 to 7.1 Φ and also a small amount of fraction with diagram higher than 63 pm.It tends to display the bimodal patterns of distribution.The grain size characteristics of the hard clay samples are very close to those of the Xiashu Loess;they show characteristics of typical eolian sediments;The discriminant parameter for the sedimentological environment calculated by the statistical parameters of grain size and the CM plots of the hard clay show the same result.Results also show that the hard clay underwent moderate chemical wreathing.The major elements such as Na and P were migrated and leached,while the elements Mn and A1 were slightly enriched during the chemical weathering process.Results reveal that the hard clay from Suzhou area have the same origin as the Xiashu Loess;it＇s a kind of aeolian deposition.In addition,the grain size and chemical characteristics of the upper hard clay are obviously different from the lower.The lower hard clay is coarse in size,and its chemical weathering intensity is much weaker than the upper.The reason is that they might have been deposited during last glacial maximum;the stronger winter monsoon severely influenced the loess of the upper hard clay.

关 键 词：粒度特征 元素地球化学 古气候 硬粘土 苏州 

分 类 号：P595[天文地球—地球化学] X142[天文地球—地质学]