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sur le développement des zones arides et semi-arides

Titre : Characteristics of Surface Sediments in the Eastern Edge of the Kubuqi Desert

Auteur : 郭鑫

Grade : Master 2022

Université : Inner Mongolia Agricultural University

Résumé partiel
The Kubuqi Desert is a typical desert in arid areas,and it is also one of the main paths of the eastward movement of sandstorms in Northwest my country.Due to the influence of natural and human factors,the surface water and soil loss is serious and the degree of desertification is intensified.Sediment characteristics record important information in the formation and evolution of aeolian sand landform,which is helpful to determine the desert sedimentary environment and material source.Taking the surface sediments on the eastern edge of Kubuqi Desert as the research object,through field investigation and using the theoretical knowledge of aeolian sand geomorphology,this thesis determines and analyzes the micro morphology,particle size and geochemical major elements of surface sediments.Based on the analysis of the characteristics of different regions and types of sediments in the eastern edge of Kubuqi Desert,the following conclusions are initially drawn :（1）The roundness of quartz grains in the surface sediments of the eastern margin of the Kubuqi Desert is mainly sub-angular and angular,and the proportion of the two is more than 70%,and the round and sub-circular grains are less.Under the physical and mechanical action,the bedrock quartz particles have experienced strong wind erosion,mechanical impact and medium and low energy underwater environment,dish-shaped craters,crescent-shaped impact craters and pitted surfaces appear in large numbers,"V"-shaped craters,straight or curved impact grooves and scratches and nicks appear in small amounts ;Quartz particles are less modified by chemical action,and the occurrence frequency of chemical genetic characteristics is low.（2）The grain size distribution of the surface sediments in the eastern margin of the Kubuqi Desert is dominated by medium sand and fine sand,with less clay,silt and very fine sand ;In terms of spatial distribution,the contents of clay,silt,very fine sand and fine sand gradually increase from north to south,while the contents of medium sand,coarse sand and very coarse sand are on the contrary.In addition,among different types of sediments,there are obvious differences in the composition of particle size gradation,among which the differentiation of mobile sand dunes and semi-fixed sand dunes is the best,followed by fixed sand dunes,and the differentiation of cultivated land and river floodplain sediments is poor ;The grain size frequency curves of different regions and types of sediments are all bimodal,and there areobvious differences under the influence of different depositional environments.

Mots clés : Surface sediment ;Particle size ;Sedimentary environment ;Chemical weathering ;Eastern margin of Kubuqi Desert ;

Présentation (CNKI)