郎溪剖面石英粒度和沉积物粒度特征对比与意义分析

在郎溪剖面全样中提取石英矿物，与原始沉积物在各粒度特征上有着显著异同。粒度组成上粉砂＞黏粒＞砂砾，而沉积物粒度黏粒含量更高且在下蜀黄土层出现不一致的分布规律；石英中值粒径偏大而二者众数粒径范围相似；石英平均粒径偏大，分选系数较好，偏度多为近对称态而沉积物粒度多为负偏态；石英峰态更加尖锐。通过引入粒度频率曲线、累积频率曲线以及粒度端元分解法对二者粒度特征做出解析，指出：石英作为稳定矿物较易保存原始沉积环境的粒度信息；红土形成时期曾遭受强风化作用导致沉积物黏粒增多；加积型红土形成环境可能与下蜀黄土存在一定差异；二者粒度参数分布虽呈现不一致的特征，但总体上都具有相同的指示性；黏粒可能由自然成壤改造作用形成；细粉砂可能是冬季风远距离搬运的沙漠黄土物质；粗粉砂可能是冬季风近距离搬运的河漫滩物质；砂砾可能是夏季风近距离搬运的粗粒跃移组分。对郎溪剖面形成时期沉积动力与沉积环境做出判断，对于印证石英与沉积物在各粒度特征上的应用性，以及恢复气候旋回背景下的古环境变化具有独特的研究意义。

Comparison and Significance Analysis of Quartz Grain Size and Sediment Grain Size in Langxi Section

Quartz minerals are extracted from the whole Langxi section, and there are significant similarities and differences in grain size characteristics with the original sediments. The particle size composition is silt > clay > gravel, while the sediment particle size and clay content are higher and the distribution law is inconsistent in the loess layer of Xiashu; the median particle size of quartz is larger and the modal particle size range is similar; The particle size is larger, the sorting coefficient is better, the skewness is mostly near-symmetric and the sediment particle size is mostly negative skew; the quartz kurtosis is more sharp. By introducing the particle size frequency curve, the cumulative frequency curve and the particle size endmember decomposition method, the particle size characteristics of the two are analyzed.It is pointed out that quartz, as a stable mineral, can easily preserve the particle size information of the original depositional environment; The formation environment of agglomerated laterite may be different from that of Xiashu loess; although the particle size parameter distributions of the two are inconsistent, they have the same indication on the whole; the clay may be transformed by natural soil formation. The fine silt may be the desert loess material transported by the winter monsoon; the coarse silt may be the floodplain material transported by the winter monsoon; the gravel may be the coarse-grained transition component transported by the summer monsoon. Judging the sedimentary dynamics and sedimentary environment during the formation of the Langxi profile has unique research significance for confirming the applicability of quartz and sediments in various grain size characteristics, and for restoring paleoenvironmental changes in the context of climate cycles.