第四纪晚期拉萨河谷地地貌演化研究  

Study on the geomorphological evolution of the Lhasa River valley during the Late Quaternary

作　　者：胡锦荣 王刚[1] 杨文光[2] 李文韬[1,3] 易子韩 胡俊晨 孙昭杰 于弋洋 HU Jinrong;WANG Gang;YANG Wenguang;LI Wentao;YI Zihan;HU Junchen;Sun Zhaojie;YU Yiyang(College of Earth and Planetary Sciences,Chengdu University of Technology,Chengdu 610059,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China;Sichuan College of Architectural Technology,Deyang 618000,China;Urumqi Jinjiang Mining Exploration Technology Service Co.,Ltd.,Urumqi 830099,China)

机构地区：[1]成都理工大学地球与行星科学学院,成都610059 [2]成都理工大学沉积地质研究院,成都610059 [3]四川建筑职业技术学院,德阳618000 [4]乌鲁木齐锦疆矿业勘查技术服务有限公司,乌鲁木齐830099

出　　处：《第四纪研究》2025年第1期34-48,共15页Quaternary Sciences

基　　金：国家自然科学基金面上项目(批准号:41372203、41972118和41002055)资助。

摘　　要：拉萨河位于青藏高原南部,是雅鲁藏布江的重要支流之一。以拉萨河谷地为研究地区,以谷地地貌为对象,综合野外实地观测、数字高程模型、卫星遥感影像以及谷地内前人和本研究的黄土光释光测年数据(118±11~82.7±8 ka)、前人研究阶地等第四系沉积物的测年数据,提出了一种以冰川作用为主的拉萨河谷地演化模式,认为现今拉萨河谷地宽阔的形态是发育在该区的一次山谷冰川侵蚀事件的产物,在该次冰川作用下,沿谷地形成开阔的“U”型谷,清空了谷地中早先可能存在的第四系沉积物,塑造了拉萨河谷地的基础。综合拉萨河谷地内第四系沉积物的年龄数据,认为该次冰川作用发生于倒数第二次冰期。伴随本次冰川的退缩和消融,谷地内充填了巨厚的中更新世晚期的冰碛物,以及晚更新世以来的冲洪积物、风成黄土等。The Lhasa River,a tributary of the Yarlung Zangbo River,flows through the southern part of the Qinghai-Tibet Plateau.The capital of the Tibet Autonomous Region,Lhasa,is situated within the Lhasa River valley.The Lhasa River flows from northeast to southwest,converging with the Yarlung Zangbo River in Qushui County.The Lhasa Valley as a whole has a Z-shaped layout,with the elevation at the bottom of the valley ranging from 3500 m to 4000 m.The higher elevation suggests that the processes of erosion and deposition by Quaternary glaciers might have existed during the evolution of this river valley's landform.We examined the geomorphological types and evolution of the Lhasa River Valley from Lhasa City to Mozhugongka County,utilizing chronological data from Quaternary deposits to assess the roles of glaciers and rivers in its geomorphological evolution.We identified glacial pavement in the valley bedrock(3833 m),and glacially eroded cirque-like landforms on both sides of the valley(at elevations ranging from 3783 m to 4008 m).We believe that the basement of the Lhasa River Valley is a U-shaped valley formed by the denudation of a mountain glacier.With the end of the ice period and the melting of the glacier,the valley was filled with a set of extremely thick moraines,later alluvial sediments and eolian loess deposits.According to the age of the moraine filling in the valley(Late Middle Pleistocene)and the burial age of the newer deposits above it(eolian loess:118±11~82.7±8 ka;terrace:20~30 ka).We believe that the glaciation that shaped the foundation of the Lhasa River Valley occurred in the penultimate glaciation,and the scope and intensity of the last glaciation in this region were lower than that of this glaciation.Our study should help to understanding the mechanisms of river valley geomorphological evolution within and surrounding the Qinghai-Tibet Plateau,as well as the coupling relationship between climate change and surface processes.

关 键 词：拉萨河 青藏高原南部 倒数第二次冰期 地貌演化 

分 类 号：P534.63[天文地球—第四纪地质学] P931.4[天文地球—古生物学与地层学]