A Study On The Symbiosis Of Crescent-shaped Dunes And Linear Dunes

Dune symbiosis is a hot issue in recent years,but most scholars have not thoroughly studied it,especially the morphological combination characteristics,development environment and causes of dune symbiosis are not well understood.In view of this,this paper uses Google Earth to identify the symbiotic regions of barchan dunes and simple linear dunes in the global desert,to obtain the distribution areas of symbiotic dunes,to measure the morphological parameters of barchan dunes and linear dunes in the symbiotic regions,to discuss and summarize the evolution environment and morphological combination characteristics of symbiotic dunes,and to classify their causes from the aspects of wind regime,sediment availability and development environment.The study of dune symbiosis not only improves our understanding of dune symbiosis and dune formation and development,but also enriches the theory of wind-sand geomorphology formation and evolution.This paper draws the following conclusions:(1)Distribution of symbiotic dunes.Globally,symbiotic dunes mainly exist in Asia,Africa and America,of which Asia and Africa are the most widely distributed.Asia is mainly distributed in the Qaidam Basin Desert and Rub al Khali Desert.Africa is mainly distributed in the Sahara Desert,and America is distributed in the Mojave Desert.(2)Morphological characteristics of symbiotic dunes.Globally,the length of barchan dunes in symbiotic dunes range from 8 to 819 m,88%is between 50 and 200 m.the width is from 6 to 481 m,75%is between 25 and 100 m.The height range from 0.7 to 29 m,76%between 2 and 9 m,the aspect ratio is from 0 to 2,and 71%is between 0 and 1 m;The length of linear dunes range from 61 to 20089 m,87%is between 61 and 3000 m.The width range from 4 to 216 m,92%is between 4 and 60 m.The height is from 1 to 50 m,89%is between 1 and 12 m.The aspect ratio is between 4 and 372,80%is between 4 and 70.In addition,there are some differences in the morphometric parameters of symbiotic dunes on different continents and in different deserts.(3)The development environment and morphological combination characteristics of symbiotic dunes.Symbiotic dunes generally developed at the edge of desert,mainly including mountains,rivers and lakes,near grasslands,as well as alluvial fan,dry salt lake bed,the sediment availability is relatively insufficient.There are different morphological combination characteristics of symbiotic dunes,which mainly include three types:The first type is barchan dunes and linear dunes,which develop in turn along the wind.The second type is barchan dunes and linear dunes which develop side by side along the wind direction.The third type is barchan dunes scattered in linear dunes or linear dunes scattered in barchan dunes.(4)Causes of symbiotic dunes.The formation of symbiotic dunes is mainly influenced by obstacles,sediment salinity,rivers,wind regime and sediment availability and other factors.However,the cause of formation of symbiotic dunes is not single,but formed by two or more factors.In general,its formation is not only caused by wind regime,but also caused by wind regime and other factor such as sand supply,obstacles and so on.