策勒绿洲-沙漠过渡带不同沙丘的沉积物粒度特征及沉积环境

目的]通过对策勒绿洲—沙漠过渡带不同沙丘类型下风沙沉积物粒度、磁化率分布特征及环境敏感粒级组分进行分析，探讨不同沙丘类型下风沙沉积物相关参数及分布规律。方法]基于绿洲—沙漠过渡带4种沙丘各部位粒度数据及磁化率数据，采用数理统计方法进行相关性分析。结果]4种沙丘在不同地貌部位表层的沙物质粒级含量有所差别，回涡、灌丛、新月形及风影沙丘表面沙物质主要由极粗粉砂、极细砂、细砂组成，百分含量总和由小到大依次为96.71%,97.54%,98.48%,98.65%。4种不同沙丘表面沙物质分选性均为分选中度好。不同沙丘的峰态平均值介于0.93～1.02,属于中等峰态，从总体上分析4种沙丘的峰态值从迎风坡底到顶部逐渐增大，顶部到背风坡底部逐渐减小。新月形沙丘偏度值最小，偏度值介于-0.03～0.01,主要表现为对称，风影、回涡及灌丛沙丘偏度值介于-0.04～0.44,为对称和正偏。风影、灌丛及新月形沙丘表面沙物质平均粒径与偏度值呈极显著正相关(p<0.01),表明沙粒平均粒径愈粗愈趋向正偏。风影、回涡及新月形沙丘表面沙物质偏度与峰态呈极显著正相关(p<0.01),沙物质分选性愈差，就...

Sediment Granularity Characteristics and Deposition Environment of Different Dunes in the Cele Oasis-Desert Ecotone

Objective]The distribution characteristics of particle size, magnetic susceptibility and environmentally sensitive grain size fractions of eolian sand sediments under different dune types in the oasis-desert ecotone were studied to explore the relevant parameters and distribution patterns of eolian sand sediments under different dune types. Methods] Based on the grain size data and susceptibility data of each part of the four kinds of sand dunes in the oasis-desert ecotone, the correlation analysis was carried out by using mathematical statistical method. Results] The surface sand contents of the four types of dunes differ in different geomorphic areas, with the surface sand content of the four types of dunes consisting mainly of very coarse silty sand, very fine sand and fine sand, with the total percentage content of 96.71%, 97.54%, 98.48% and 98.65%, respectively. All the four different dunes have moderately good sortability of surface sand material. The mean kurtosis values of the different dunes range from 0.93 to 1.02, which is a medium kurtosis. In general, the kurtosis values of the four dunes increase gradually from the bottom to the top of the windward slope and decrease from the top to the bottom of the leeward slope. The crescent-shaped dunes have the lowest kurtosis values, ranging from-0.03 to 0.01, which are mainly symmetrical, while kurtosis values of the wind shadow, gyre and scrub range from-0.04 to 0.44, which are mainly symmetrical and positively skewed. The mean grain sizes of sand material on the surface of wind shadow dunes, scrub dunes and crescent dunes show the highly significant positive correlation(p<0.01)with the skewness value, indicating that the coarser the mean grain size is, the more positive the skewness tends to be. A highly significant positive correlation(p<0.01)is found between the skewness and kurtosis of the sand material on the surface of the wind-shaded, scrub and crescent dunes, indicating that the poorer the sand material sorting is, the more narrowly kurtotic the sand material tends to be. The four different dune environments have sensitive grain size fractions concentrating in the range of 100～570 μm, indicating strong wind and sand activity in the study area, and large differences in the relative variation of grain size-standard deviation values of the samples due to the differential structure and anthropogenic causes of the geographical elements. Conclusion] The differences in grain size between the four dune types in the oasis-desert ecotone are mainly due to topography, wind conditions and the structure of the sand source sediments.