雅鲁藏布江中游古洪水滞流沉积物性质研究  

Characteristics of the Palaeoflood Slackwater Deposits in the Middle Reaches of the Yarlung Zangbo River

作　　者：吴帅虎 傅旭东[2] WU Shuai-hu;FU Xu-dong(School of Resources Environment and Tourism,Anyang Normal University,Anyang 455000,China;State Key Laboratory of Hydroscience and Engineering,Tsinghua University,Beijing 100084,China)

机构地区：[1]安阳师范学院资源环境与旅游学院,河南安阳455000 [2]清华大学水沙科学与水利水电工程国家重点实验室,北京100084

出　　处：《长江流域资源与环境》2023年第5期1058-1067,共10页Resources and Environment in the Yangtze Basin

基　　金：国家自然科学基金重点项目(91747027);河南省自然科学基金青年项目(212300410101)。

摘　　要：对在雅鲁藏布江中游河谷鉴别的古洪水滞流沉积物(SWD)、黄土和风沙沉积物进行宏观特征观察和沉积物实验分析(粒度、磁化率和地球化学元素),总结古洪水SWD的沉积学识别标志。结果发现:藏木(ZM)、朗县(LX)和米林剖面(ML)中所夹SWD均呈现水平波状层理,结构均匀,为粉砂质细砂质地,其宏观特征与风成堆积物(如黄土和风沙沉积物)明显不同;古洪水SWD、黄土和风沙沉积物的粒度成分均总体较粗,以细砂为主,风沙沉积物的粒径明显更粗,三种沉积物中以古洪水SWD的分选性最好,其次为黄土,其原因在于古洪水SWD是经过水流分选并且在高水位滞流环境下堆积的悬移质沉积物;古洪水SWD的磁化率含量较高,可能与洪水冲刷河谷地表导致SWD的铁磁性矿物含量增高有关;古洪水SWD的粒度特征、常量元素和微量元素含量均与黄土较为接近,与风沙沉积物有较大差别,表明雅鲁藏布江中游峡谷地段古洪水SWD与黄土的物源可能有密切关系。In this study,paleoflood slackwater deposits(SWD),loess and aeolian sand were surveyed and sampled in the middle reaches of the Yarlung Zangbo River valley in the Tibetan Plateau in China.Their macroscopic characteristics were observed and sediment experimental analyses(i.e.,grain size,magnetic susceptibility and geochemical elements)were conducted.The primary goal of the study is to summarize the sedimentological identification marks of the paleoflood SWD in the middle reaches of the Yarlung Zangbo River valley in the Tibetan Plateau in China.Results showed that the SWD trapped in the Zangmu profile(ZM),Langxian profile(LX)and Milin profile(ML)all demonstrated horizontal wavy lamination with uniform structure and its macroscopic characteristics are obviously different from those of the aeolian deposits(e.g.,loess and aeolian sand).The grain size composition of the paleoflood SWD,loess and aeolian sand are generally coarse,mainly fine sand(>0.063 mm).Among them,the grain size of the aeolian sand is obviously coarser than that of the paleoflood SWD and loess.The sortability of the paleoflood SWD is the best among the three sediments,followed by loess,and aeolian sand in the middle reaches of the Yarlung Zangbo River valley in the Tibetan Plateau in China.The reason is that the paleoflood SWD is a suspended sediment sorted by water.The higher magnetic susceptibility content of the paleoflood SWD is probably related to the increase of ferromagnetic minerals in SWD due to the surface scouring of the middle reaches of the Yarlung Zangbo River valley by floods.The grain size characteristics,major and trace element contents of the paleoflood SWD are close to those of the loess in the middle reaches of the Yarlung Zangbo River valley in the Tibetan Plateau in China.However,there are obvious different occurred in the grain size characteristics and major and trace element contents between the paleoflood SWD and aeolian sand.These suggested that the sediment provenance of the paleoflood SWD may be closely related with that

关 键 词：雅鲁藏布江 古洪水 滞流沉积物 

分 类 号：P539.6[天文地球—古生物学与地层学]