摘要
对受西风控制的新疆伊犁地区的黄土和黄土状土系统粒度分析资料表明，二者既有相近之处，也具有明显差别。首先，黄土与黄土状土粒度组成都以粉砂（５０—５μｍ）含量（５８％～８５％）占优势，但黄土状土砂含量较黄土低，而粘粒含量却较黄土高；第二，黄土与黄土状土众数分布位置相近（１５－３０μｍ），但粒组绝对含量相差较大，黄土状土其值最高可达 ５０％，而黄土均未超过 ２０％。黄土粒度频率曲线呈正偏态，黄土状上为极正偏；第三，黄土状士因粘粒含量高而使平均值较黄土细偏，分选较黄土差，在平均值对分选系数、偏度对平均值等图解参数散点图中，黄土与黄土状土样品分别位于不同的区域。因此认为，黄土与水成的黄土状土具有不同的搬运、分选机制和沉积环境，伊犁地区的黄土沉积为风成。
Yili area is located in the west of Xinjiang and is an intermountane basin of Tianshan, in which the loess is widespread. Only a few studies were carried out during past decades. For this reason, there are different opinions on the origin of loess. The results of grain size analysis of loess and reworked loess show that the textural features of both are same on one side and different on the other side. Firstly, the composition of grain size of loess is similar to that of the reworked loess, but the sand particles of loess is higher and the clay particles is lower than that of reworked loess. Secondly, the frequency curve of loess and reworked loess occures to be positive normal distribution. The mode of both locates in the range of 15-30μm, but the percentages are different. The amount of loess is less than 20 %, while the maxmum percentage of reworked loess reaches 50 %. Thirdly, the sorting of loess is better than that of the reworked loess, even though both are poor sorting deposits. The skewness of loess ranges from 0. 13 to 0. 43 and most of them is lower than 0. 3. Comparied with the loess, the skewness of reworked loess is higher and the mediun size moves toward coarse side. The kurtosis of loess is medium, while peak of reworked loess is steep. In summary, the loess and the reworked loess were transported and sorted by different dynamics before the dust deposited. In addition, the depositing environments were also different. The evidences from the grain size show the loess in Yili area is a typical eolian deposit.
出处
《干旱区地理》
CSCD
北大核心
2000年第4期310-314,共5页
Arid Land Geography
基金
国家自然科学基金项目!(49671009)
国家重点基础研究发展规划项目!(G1999043502)资助
