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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5.2~7.1Φ,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。
The Late Pleistocene hard clay formation in the Yangtze River Delta is of great significance for understanding the environmental changes in the Late Pleistocene and the construction of modern engineering in this area. In this paper, particle size and elemental geochemistry of hard-clay samples from Sinting Boulevard in Suzhou area are analyzed, and their causes and paleoenvironmental significance are discussed. The results show that: (1) The average particle size of hard clay in Suzhou area is 5.2 ~ 7.1Φ, with silt particles as the main component. The contents of medium and fine silt particles are above 65%, and the frequency curve is bimodal. The particle size distribution is (2) The environmental discrimination shows that it is an aeolian deposit, which is similar to the distribution characteristics of Xiashuashu loess in Nanjing and Zhenjiang; (3) The elemental analysis shows that Na, P elemental loss occurs in the hard clay And Mn and Al are enriched and the chemical weathering is in the middle stage of weathering. (4) There is a clear difference in grain size and elemental characteristics between the upper and lower sections of the hard clay layer. The grain size of the lower section is obviously thicker and the weathering degree is relatively weaker.