Study On The Development Environment And Formation Age Of Linear Sand Dunes In Sebei Area Of Qaidam Basin

In recent years,it has been found that linear dunes are also distributed on Mars,Venus,Titan and other planets.At present,there are still controversies about the formation and development of linear dunes in the world,mainly divided into erosion and accumulation causes.Therefore,the research on linear dunes has become a hot spot.Linear dunes have various forms,and a single theory cannot fully explain all their characteristics and formation and evolution process.Their formation is influenced by sand source,sedimentary environment,underlying surface conditions and regional wind conditions.However,wind is the main external force for shaping sand dunes.Studying the characteristics of wind conditions in a region is helpful for understanding the development environment of linear dunes in the region.Studying the formation age of linear dune is helpful to understand its longitudinal extension and velocity,lateral movement process and velocity,vertical accretion and velocity.Therefore,it provides theoretical support for the formation and development of linear dunes.Qaidam Basin is one of the most typical distribution areas of linear dunes in China.In this paper,linear dunes in Sebei area of Qaidam Basin are selected as the research object for field investigation.An automatic meteorological observation instrument is set up in the research area.Wind condition data,including wind speed and direction,are collected.Two representative linear dunes were selected,the profile was excavated and samples were collected,and the surface layer and profile of the linear dunes in Sebei area of Qaidam Basin in the direction of extension were dated by using optical emission light(OSL)dating method.Finally,based on the study of wind conditions and formation age of linear dunes in Sebei area of Qaidam Basin,the development environment and evolution process of linear dunes in the study area are comprehensively analyzed.Get the following preliminary understanding:(1)Through the analysis of wind data in the study area,the wind energy environment in which linear dunes develop in the study area is discussed.It can be seen that WNW and NW wind are the main wind directions for sand-raising in linear dunes in Sebei area of Qaidam Basin,accounting for 31.8%and 24.40%respectively,while the other sand-raising wind directions account for a small proportion,indicating that the sand-raising wind direction in the study area has a small variation range and a single wind direction.The monthly average wind speed and the maximum wind speed of the sandstorm reach the maximum in spring,which indicates that the sandstorm activity in spring in this research area is strong,and is mainly westerly in northwest,with severe wind erosion.Through calculation,it can be concluded that the annual sediment transport potential(DP)in the study area is 325.5VU,the synthetic sediment transport potential is 219.48VU,the corresponding wind energy environment is medium wind energy environment,the direction change rate index(RDP/DP)is0.68,and the corresponding wind direction change rate is medium change rate,which is blunt/sharp bimodal wind condition environment.(2)Through the comprehensive analysis of the profile of the linear dune in the study area through field investigation,it can be seen that the cross-sectional shape.The bottom of the dune is relatively flat,and the slope increases with the increase of dune height.The average trend of linear dunes in the study area is WN-SE 122°,which is in good agreement with the wind direction of sand-producing wind in this area and has a certain included angle with the direction of synthetic sand transport potential(127.7°).(3)Dating of linear dunes in Sebei area of Qaidam Basin shows that the linear dunes in the study area have a longitudinal extension from northwest to southeast during formation,with an average extension speed of 0.35 m a^-1;There is a lateral movement from northeast to east and from southwest to west,with an average movement speed of 0.008 m a^-1.There is a vertical accretion process in the vertical direction,and the average velocity of vertical accretion is 0.0013 m a^-1.