Contribution of underlying terrain to sand dunes: evidence from the Qaidam Basin, Northwest China  

作　　者：LI Jiyan QU Xin DONG Zhibao CAI Yingying LIU Min REN Xiaozong CUI Xujia 

机构地区：[1]School of Geography Science,Taiyuan Normal University,Jinzhong 030619,China [2]School of Geography and Tourism,Shaanxi Normal University,Xi'an 710119,China

出　　处：《Journal of Arid Land》2021年第12期1215-1229,共15页干旱区科学（英文版）

基　　金：The study was funded by the National Natural Science Foundation of China(41601005,41930641);the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province(2019L0797).

摘　　要：Underlying terrain strongly influences dune formation.However,the impacts of underlying terrain on the dune formation are poorly studied.In the present research,we focused on dunes that formed in the alluvial fans and dry salt flats in the Qaidam Basin,Northwest China.We quantified the dunes'sediment characteristics on different types of underlying terrain and the terrain's effects on the surface quartz grains by analyzing grain-size distribution,soluble salt contents and grain surface micro-textures.Results showed that barchan dunes were dominated by medium sands with a unimodal frequency distribution,whose peak corresponded to the saltation load.Linear dunes were mainly composed of fine sands with a bimodal frequency distribution,whose main peak represented the saltation load,and whose secondary peak represented the modified saltation or suspension load.Sand was transported from source area by running water(inland rivers)over short distances and by wind over relatively longer distances.Thus,quartz grains had poor roundness and were dominated by sub-angular and angular shapes.Surface micro-textures indicated that dune sands were successively transported by exogenic agents(glaciation,fluviation and wind).Soluble salt contents were low in dunes that developed in the alluvial fans,which represented a low-energy chemical environment,so the grain surface micro-textures mainly resulted from mechanical erosion,with weak micro-textures formed by SiO2 solution and precipitation.However,soluble salt contents were much higher in dunes that developed in the dry salt flats,which indicated a high-energy chemical environment.Therefore,in addition to micro-structures caused by mechanical erosion,micro-textures formed by SiO2 solution and precipitation also well developed.Our results improve understanding of the sediment characteristics of dune sands and the effects of underlying terrain on dune development in the Qaidam Basin,China.

关 键 词：DUNE grain-size distribution soluble salts surface micro-texture Qaidam Basin 

分 类 号：P931.3[天文地球—自然地理学]