贵州双河洞国家地质公园洞穴冲积物的粒度组成及环境意义——以山王洞为例

Grain Size Characteristics and Environmental Significance of the Cave Alluvium in the Shuanghe Cave National Geopark of Guizhou Province——A Case Study of the Shanwang Cave

通过采集双河洞国家地质公园的山王洞洞穴冲积物，利用Mastersizer2000对40个沉积物样品的粒度进行测试分析并计算平均粒径（Mz）、标准偏差（σ I）、偏度（SK I）和峰度（K G）等相关参数。结果表明：（1）山王洞地下古河道沉积物优势粒级以粉砂、黏土为主，其含量占总体水平的70％以上，整个冲积剖面表现为2套（9—1号与40～31号样品）由粗到细变化的砂体相互叠置和1套（30—10号样品）粒级含量相对稳定且粒级较小的砂体构成；（2）山王洞冲积物分选性差，具有河成沉积物的特点，冲积物粒径大小表明可能存在两个降雨量较大阶段和一个降雨量较小阶段；（3）沉积物颗粒较地表河沉积粒度细且分布集中，悬浮总体的累积百分含量高，反映洞穴古河道河流总体水位稳定或水动力较弱，可能与洞穴流域范围内地表植被好，地表侵蚀不严重有关。

Through sampling alluvium from the Shanwang Cave in the Shuanghe Cave National Geopark,testing the grain size of 40 samples by Mastersizer 2000 and counting M z, σ I , SK I, K G, etc, we found that： （1）silt and clay are the dominant grain fractions of sediments in the Shanwang Cave ancient underground channel, whose content level is over 70%. The alluvium section is composed of two series of sand whose size varies from big to small （samples from 9th to 1th and 40th to 31th ）and one series whose size is small and the grain size level is uniform （samples from 30th to 10th） ; （2）the size classification level is low, whose characteristics are similar to river deposition and the progress of deposition possibly has two stages of strong rainfall and one stage of weak rainfall; （3）the grain size is smaller and the concentrated distrihution is compared with the grain size of river deposition, and the suspension component level of deposition is high, which makes it clear that the water level of cave river is steady or shows a weakly hydrodynamic force, the ground vegetation is better and soil erosion is weak in the watershed range as well.