Characteristics Of Surface Sediments And Its Environmental Significance In The Takermohuer Desert Of Xinjiang

The characteristics of aeolian sand deposits record the important information of desert formation and evolution,which can reflect the sedimentary environment to a certain extent.Taking the surface sediments of Typical Shrub dunes and parabolic dunes developed in Takermohuer Desert of Xinjiang as the main research object,the grain size and magnetic susceptibility were discussed by field investigation,sampling and laboratory grain size and magnetic susceptibility experimental analysis.The preliminary results of environmental information reflected by chemical index are as follows:(1)The total particle size distribution of 187 surface sediments in the Takermohuer Desert ranges from 1.78 um to 2116.54?m,and there are>2000?m particles.The grain size is mainly composed of medium sand,fine sand and very fine sand.Crude sand dominated,the total volume percentage reached 97.71%,of which the medium sand content varied between 19.05-60.37%,the average content was 43.05%;the fine sand content ranged from 10.94-63.06%,the average content was 42.54%;The fine sand content is between 0-21.34%and the average content is6.10%;the coarse sand content varies from 0-32.26%,and the average content is6.02%.(2)Characteristics of total grain size parameters of 187 surface sediments in the Takermohuer Desert:The average particle size distribution ranged from 1.28 to 2.55?(170.25 to 412.13?m)with an average value of 2.02?,which belongs to the fine sand range.The sorting coefficient varies between 0.50 and 1.16,with an average of0.66?,which belongs to Moderately Well Sorted.The skewness value varies from-0.08 to 0.41,and the range includes Symmetrical,Fine Skewed and Very Fine Skewed.The average value of the skewness is 0.06?is near symmetry.The kurtosis values are distributed between 0.92?and 2.57?,and the range is Mesokurtic,Leptokurtic,Very Leptokurtic,and the average of the kurtosis is 1.00?belongs to Mesokurtic.(3)Grain size characteristics of surface sediments of shrub dunes and parabolic dunes in the study area:Compared with the two types of dunes,the change of grain size content is similar,but there are only slight differences in the smaller grain size.The mechanical composition is mainly coarse sand,medium sand,fine sand and very fine sand.Among them,the volume percentage of coarse sand and medium sand in shrub dunes is higher than that in parabolic dunes,and the content of fine sand and very fine sand is higher than that in parabolic dunes.In terms of grain size parameters,the average grain size,mode value and median grain size of parabolic dunes are slightly larger than the whole value of the study area,belonging to the fine sand range,while the average grain size,median value and mode value of shrub dunes are slightly smaller than the whole value of the study area,belonging to the medium sand range;that is,the average grain size of parabolic dunes in the study area is smaller than that of shrub dunes.The sorting coefficients,skewness and kurtosis show slight differences,which belong to better sorting,nearly symmetrical skewness and Mesokurtic.(4)In the correlation analysis of the average particle size,sorting coefficient,skewness and kurtosis of the surface sediments in the study area,it is found that,except for the mean particle size and the sorting coefficient,the other parameters are between any two.A positive correlation is presented,in which the correlation between kurtosis and skewness is the largest,and the positive correlation between the particle size parameters is as follows:the mean particle size of the particle becomes larger,that is,when the particle becomes thinner,the skew is Fine Skewed.The kurtosis is also narrower.The overall particle size frequency curve of the study area is mainly monomodal,and there are weak secondary peaks at the finer end of the particle,indicating that the wind dynamic mechanism is stable or the transporting gravity is relatively simple.The probability cumulative curve shows a typical three-stage distribution,and the surface sediments are mainly The main component of the jump is about 1-3?.(5)Magnetic parameters of surface sediments in the Takermohuer Desert:The susceptibility of 187 surface sediments in the study area varies from 51.22 to 212.85×10^-8m³/kg,with an average of 94.66×10^-8m³/kg,the high-frequency mass magnetic susceptibility varies from 50.37 to 210.55×10^-8m³/kg,the average value is 93.97×10^-8m³/kg,and the frequency susceptibility varies from 0.02-2.65%,the average value of 0.76%<2%,indicating that the magnetic minerals in the sediments of the study area are mainly MD,containing a small amount of SP particle size.The mean magnetic susceptibility of parabolic sand dunes in the two types of dunes analyzed is larger than that of shrub sand dunes,while the mean frequency susceptibility is larger than that of shrub sand dunes.(6)Correlation analysis between magnetic susceptibility and different grain groups of sand and silt found that there is no significant correlation between the mass magnetic susceptibility and frequency susceptibility of surface sediments in the study area and sand and silt,its magnetic minerals It is not enriched in a certain particle group,but distributed in different grain size compositions.The source of magnetic minerals may have multiple sources.The average particle size and median diameter(?)mass magnetic susceptibility are significantly positively correlated,and the fine particle composition determines the content of magnetic minerals to some extent.The particle size parameters of the study area reflect the rich environmental information.According to the Sahu(1964)discriminant formula,the sedimentary environment of the Takermohuer Desert is complex,and the four types of sedimentary environments are distributed,further indicating the surface sediment sources in the study area are diverse.