汉江上游罗家滩剖面晚更新世以来沉积物粒度端元分析  

Grain size end member analysis of the Late Pleistocene and Holocene sediments in the Luojiatan profile on the upper Hanjiang River

作　　者：潘昭烨 张玉柱 黄春长 庞奖励 查小春 周亚利 朱艳 贾雅娜 王浩宇 陈豆 肖奇立 王春梅 PAN Zhaoye;ZHANG Yuzhu;HUANG Chunchang;PANG Jiangli;ZHA Xiaochun;ZHOU Yali;ZHU Yan;JIA Yana;WANG Haoyu;CHEN Dou;XIAO Qili;WANG Chunmei(College of Urban and Environmental Sciences,Northwest University,Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity,Xi’an 710127,China;School of Geography and Tourism,Shaanxi Normal University,Xi’an 710119,China;State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences,Xi’an 710061,China)

机构地区：[1]西北大学城市与环境学院,陕西省地表系统与环境承载力重点实验室,西安710127 [2]陕西师范大学地理科学与旅游学院,西安710119 [3]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,西安710061

出　　处：《地球环境学报》2022年第6期702-713,共12页Journal of Earth Environment

基　　金：国家自然科学基金项目(42277449,41977062,41971116);黄土与第四纪地质国家重点实验室开放基金(SKLLQG2107)。

摘　　要：通过对汉江上游旬阳段开展野外考察,在罗家滩(LJT)发现夹有古洪水滞流沉积层(slackwater deposits,SWD)的风成黄土-古土壤剖面。对采集的沉积学样品进行粒度分析,利用Gen.Weibull函数分布的参数化端元模型反演得出4个端元,结合吸湿水等环境替代指标分析,探讨了各个端元所指示的不同沉积动力环境和物质来源。结果表明:在黄土层和土壤层中,EM1代表的主要是沉积物沉积后在亚洲夏季风影响下,经历强烈风化成壤作用形成的次生黏土矿物组分;EM2代表高空西风和东亚冬季风翻越秦岭而搬运的远源细粉砂组分;EM3代表山谷风从河谷中分布的河流沉积物和坡积碎屑物中以低空短距离形式搬运而来的粉尘物质,并且受到后期气候变化控制下的淋溶作用影响;EM4则代表山谷风从近源的河流沉积物和坡积碎屑物中搬运而来的粗颗粒物质。在古洪水SWD层中,EM1、EM2和EM3主要来源于汉江上游暴雨洪水侵蚀搬运的河谷两岸分布的表层沉积物;而EM4则明确代表河流特大/大洪水环境下搬运沉积的粗颗粒悬移质泥沙。该成果能够为区域环境变化研究提供指导和借鉴。Background,aim,and scope Determining the material source of the aeolian loess-paleosol succession on the upper reaches of Hanjiang River can not only reveal rich information on the evolution of the Asian monsoon climate,but also help to understand the responses of extreme climatic and hydrological events in the basin to global climate change.The end member(EM)model can be used to identify sensitive grain size components of different material sources and sedimentary dynamic processes from sediments,and further reveal changes of the regional sedimentary environment.In this study,the parametric method was used to decompose the end member model of the Luojiatan(LJT)profile in the Xunyang section of the upper Hanjiang River.Based on these results combined with comprehensive analysis of environmental substitution indexes,such as hygroscopic water and geochemical elements,the different depository dynamic environments and material sources indicated by each end member were identified,and the sedimentological records of major flood events in the section were accurately identified.Materials and methods A total of 198 samples were collected from the LJT profile for grain size testing.After pretreatment,the grain size distributions were measured by a LS13320 laser particle size analyzer produced by Beckman Coulter,USA,with a detection range of 0.4—2000μm.The results were analyzed by the AnalySize program based on MATLAB software,provided by Paterson and Heslop(2015).We calculated the chemical index of alteration(CIA),leaching coefficient,Rb/Sr ratio,and hygroscopic water of the above samples to assist in the determination of the source components.Results The grain size composition of the LJT profile could be decomposed into four main end members using the parametric method.The modal grain sizes of the four end members in the LJT profile were EM1=3.81μm,EM2=8.60μm,EM3=27.16μm,and EM4=103.87μm.Discussion According to the Sheppard triangle classification diagram,the loess samples from the LJT profile of the Xunyang sectio

关 键 词：环境变化 端元分析 粒度 风成黄土 汉江上游 

分 类 号：P534.631[天文地球—第四纪地质学] P512.2[天文地球—古生物学与地层学]