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额济纳旗两种地貌类型戈壁纵剖面沉积物粒度特征
1,2, 1,2, 1,2, 3

(1.zhongguokexueyuan dilikexueyuziyuanyanjiusuoludishuixunhuanjidibiaoguochengzhongdianshiyanshi, beijing 100101; 2.zhongguokexueyuandaxue, beijing 100049; 3.hebeilangfangshihuanjingjiancezhongxin, hebei langfang 065000)

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Characteristics of Grain Sizes of Sediments in Two Typical Regions of Ejina Gobi
XIAO Jingan1,2, PEI Liang1,2, SUN Liying1,2, MA Wenxiu3

(1.institute of geographic sciences and natural resources research, chinese academy of sciences, beijing 100101, china; 2.university of chinese academy of sciences, beijing 100049, china; 3.hebei langfang environmental monitoring center, langfang, hebei 065000, china)

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备注

采用野外实地调查取样与室内粒度测试结合的方法,通过矩法计算平均粒径、分选系数、偏度、峰态等粒度参数对额济纳旗戈壁两种地貌类型纵剖面沉积物粒度特征进行分析,采用独立样本均值t检验判断两种地貌类型沉积物粒度组成与粒度参数有无显著差异。结果表明:(1)湖岸上层沉积物颗粒以砾石和沙子为主,其余剖面层以沙子和粉土为主,古河道0—10 cm层沉积物颗粒主要以沙子为主,10—20 cm层沉积物颗粒主要以砾石和沙子为主,湖岸沉积物较古河道沉积物,黏土、粉土含量显著更高,沙子含量接近,砾石含量显著更低;(2)湖岸沉积物沿纵剖面方向,平均粒径变大,颗粒逐渐细化; 古河道整个采样层均为砾石与沙混合,上下层平均粒径接近,下层较上层颗粒更粗; 湖岸平均粒径显著大于古河道;(3)两种地貌类型分选系数无显著差异,分选状况均呈分选差或分选较差;(4)两种地貌类型沉积物偏度均以正偏、极正偏占主导,主要以侵蚀过程为主,颗粒粗化明显;(5)两种地貌类型沉积物粒度频率曲线均以很宽平和非常宽平为主。总之,两种地貌类型戈壁纵剖面沉积物的粒度特征整体呈平均粒径由粗变细,分选差或较差,偏度呈正偏、极正偏分布,峰态很宽平和非常宽平的特点,湖岸采样点平均粒径显著大于古河道采样点,分选系数、偏度、峰态则无显著差异,综合反映了两种地貌类型戈壁不同层次颗粒的沉积环境、侵蚀与堆积方式的异同,可为戈壁类型划分提供依据。
By using the method of field survey and indoor particle size test, the particle size parameters such as average particle size, sorting coefficient, skewness and kurtosis were calculated by the moment method to analyze the grain size characteristics of the two typical regional vertical profiles in the Gobi of Ejina Banner. The independent sample mean test is used to determine whether there is significant difference between the grain size composition and parameters of the two types of geomorphic sediments. The results show that:(1)the grain size of the sampling points along the vertical direction of the profile is gradually refined from top to bottom; the average grain size of the upper and lower layers of the ancient river channel sampling points is similar, sand is mainly dominant in 0—10 cm layer, and gravel and sand are mainly dominant in 10—20 cm layer;(2)the sorting coefficient of the sediment particles at the sampling points of the two geomorphic types is poor or much poorer;(3)the sediment skewness of the sampling points of the two geomorphic types is positive skew;(4)the frequency curve of sediment particle size is mainly very wide and very wide;(5)there is significant difference in the percentage of clay, silt and gravel components in the Gobi sediment of the two geomorphic types, and there is no significant difference in the percentage of sand components; in the particle size parameters, there is significant difference in the average particle size, and there is no significant difference in the sorting coefficient, skewness and kurtosis Sexual differences. All in all, the sediment profiles of gobi appeares the characteristics of fine average grain size, poor or pooer sorting coefficient, positive skewness and extremely positive skewness, wide flat kurtosis and very flat kurtosis, the average grain size of lake bank sampling points is significantly larger than that of paleochannel sampling points, while sorting coefficient, skewness and peak state have no significant difference. It comprehensively reflects the similarities and differences of sedimentary environment, erosion and accumulation mode of particles in different layers of Gobi of two geomorphic types, which can provide basis for gobi classification.
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