甘肃青土湖地区不同类型沙丘的表沙理化特征及其环境意义  

Physical and chemical characteristics of surface sand in different types of dunes in Qingtu Lake,Gansu,NW China,and their environmental implications

作　　者：潘美慧[1] 李娜 龚逸夫 陈晴 赵慧敏 王金雨 PAN Meihui;LI Na;GONG Yifu;CHEN Qing;ZHAO Huimin;WANG Jinyu(College of Geography and Environment Science,Northwest Normal University,Lanzhou 730070,China)

机构地区：[1]西北师范大学地理与环境科学学院,兰州730070

出　　处：《海洋地质与第四纪地质》2024年第2期69-80,共12页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金“西藏定结地区全新世风沙地貌格局与变化”(4180071858)。

摘　　要：沙丘表层沉积物的理化特征在揭示风沙的来源、沉积过程、风化作用等方面具有重要作用。本研究采用野外实地采样和实验室分析方法分析了甘肃青土湖地区不同类型沙丘表层沉积物的粒度和地球化学特征。结果表明:(1)青土湖地区沙丘表层沉积物以细砂为优势粒级,平均含量达72.08%,其次为极细砂,黏粒成分很少。频率分布曲线为单峰分布,概率累积曲线表现为三段式,反映出沉积环境较为稳定。(2)研究区沙丘表层沉积物常量元素以SiO2为主,平均含量为76.40%,其次为Al2O3和CaO,平均含量分别为5.05%、3.74%。微量元素以Cr、Mn、Co、Sr、Ba、Ti、Ce和P为主,平均含量均>100 mg/L。(3)Y、Zr和Y/Zr、Rb/Zr双变量图、A-CNK-FM图解表明巴丹吉林沙漠和腾格里沙漠为其沙源。风沙搬运过程中的磨蚀、风选作用是研究区富集Fe、Mg元素的主要原因。此外,下伏湖相沉积物就地起砂,石羊河冲积物也为其提供了部分沙物质。(4)A-CN-K和A-CNK-FM三角模式图表明研究区风化程度较弱,处于初期脱Na、Ca阶段。在沙丘固定过程中成土作用增强但淋溶作用减小,这是由于植被的影响导致半固定、固定沙丘Na、Ca含量较高。The physical and chemical imprints of surface sediments bear key information of the origination,sedimentation,and weathering of sand.Field sampling and laboratory analysis were conducted to investigate the grain size and geochemical characteristics of surface sediment with various types of sand in the Qingtu Lake,Gansu,NW China.Results show that the surface sediment is dominated by fine sand,taking an average content of 72.08%,followed by very fine sand and a minimal amount of clay.The frequency distribution curve exhibits a unimodal distribution,while the cumulative probability curve shows a three-portion pattern,indicating a relatively stable sediment environment.The predominant constant elements are mainly SiO2,occupying 76.40%in average and then Al2O3 and CaO,for 5.05%and 3.74%,respectively.The trace elements consist mainly of Cr,Mn,Co,Sr,Ba,Ti,Ce,and P,in average concentration of over 100 mg/L.The two-variable chart(Y verse Zr,Y/Zr verse Rb/Zr)and the A-CNK-FM graph demonstrate that the Badain Jaran Desert and Tengger Desert were key sand sources for the study area.The abrasion and wind erosion in sand transportation are the main factors affecting the distribution of Fe and Mg elements.In addition,lacustrine and alluvial deposits of the Shiyang River also provided a part of the sand source.The ternary diagrams A-CN-K and ACNK-FM indicate that the study area experienced weaker wind levels during the early phases of de-Na and de-Ca processes.However,in the progress of sand fixation,pedogenesis was enhanced while eluviation was reduced due to the influence of vegetation,which caused semi-fixed and fixed sand with higher Na and Ca contents.

关 键 词：沙丘 粒度特征 地球化学元素 风成沉积 风化作用 青土湖 

分 类 号：P531[天文地球—古生物学与地层学]