黄河玛曲段晚全新世古洪水事件沉积记录及其气候背景研究  

Sedimentary records and climatic background of Late Holocene palaeoflood events in the Maqu reaches of the Yellow River

作　　者：刘阳 李瑜琴 黄春长 庞奖励 查小春 周亚利 温煜未 LIU Yang;LI Yuqin;HUANG Chunchang;PANG Jiangli;ZHA Xiaochun;ZHOU Yali;WEN Yuwei(School of Geography and Tourism,Shaanxi Normal University,Xi'an 710119,China)

机构地区：[1]陕西师范大学地理科学与旅游学院,西安710119

出　　处：《地理研究》2023年第12期3147-3164,共18页Geographical Research

基　　金：国家自然科学基金项目(42171092、41971116、42271046)。

摘　　要：黄河玛曲段古洪水事件是黄河源区水系对区域气候变化的响应。基于黄河源区野外考察,在玛曲段黄河左岸一级阶地上发现夹有典型古洪水滞流沉积层的剖面。结合地层野外沉积学宏观特征和室内沉积样品磁化率、粒度分布、粒度端元、地球化学元素指标的微观特征,判定该剖面古洪水沉积层为黄河全新世古洪水滞流沉积物,且古洪水沉积层SWD2所指示的古洪水规模大于古洪水沉积层SWD1。古洪水沉积层SWD1和SWD2的OSL测年结果分别为3.33±0.15 ka和2.96±0.16 ka,表明剖面记录的两次古洪水发生于2.9 ka~3.3 ka之间,该时期恰好对应全新世晚期气候转折期。这一时期黄河源区的气候极不稳定,气候变率增大,可能有高山冰川大量消融,叠加突发性大暴雨,大量地表径流短时期汇入黄河干流河道,导致黄河玛曲段特大古洪水事件的发生。该研究成果有助于摸清黄河源区水文特征对于全球变化的响应规律以及深入理解黄河现代水系格局发育演变过程。Palaeoflood is a response of drainage systems to the regional climate change in the source region of the Yellow River.Based on field investigations of the study region,a profile with typical palaeoflood slackwater deposits(SWDs)was found on the first terrace of the left bank in the Maqu reaches of the Yellow River.Combined with macroscopic observations in the field,in particular the sedimentological characteristics,and microscopic examinations of samples in the laboratory with the characteristics of magnetic susceptibilities,grain-size distributions and end-members,and geochemical parameters,the palaeoflood slackwater deposits(SWDs)of the Yellow River were distinguished from other deposits in the profile.Furthermore,the palaeoflood level indicated by the palaeoflood SWD2 was higher than that of the palaeoflood SWD1.Based on the OSL dating and Bacon age-depth model simulation,chronologies of SWD1 and SWD2 were 3.33±0.15 ka BP and 2.96±0.16 ka BP,respectively.This indicated that two palaeofloods events recorded by SWDs in the profile occurred during 2.9-3.3 ka BP,which corresponded to the transition from the Middle Holocene to the Late Holocene.During the period,the climate in the source region of the Yellow River was relatively unstable,and its variability increased,together with the glacier melting and heavy rainfalls.A large amount of surface runoffs flowed into the mainstream of the Yellow River in a short time,which resulted in occurrences of palaeoflood events in the Maqu reaches of the Yellow River.Results are helpful to understand the hydrological response of the Yellow River to climate change in the source region,and the evolution of the present drainage systems of the Yellow River.

关 键 词：古洪水沉积 全新世晚期 气候突变 黄河源区 

分 类 号：TV122[水利工程—水文学及水资源] P534.632[天文地球—第四纪地质学] P532[天文地球—古生物学与地层学]