PROGRESS IN GEOGRAPHY ›› 2022, Vol. 41 ›› Issue (8): 1453-1466.doi: 10.18306/dlkxjz.2022.08.009

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Sedimentary evidence and age of the Zoige Basin dissected by the Yellow River in eastern Tibetan Plateau

WANG Na1(), ZHA Xiaochun1,*(), HUANG Chunchang1, ZHANG Yuzhu2, ZHOU Yali1, PANG Jiangli1, RONG Xiaoqing3, SHANG Ruiqing1, CHAI Jianan1   

  1. 1. School of Geography and Tourism, Shaanxi Normal University, Xi'an 710119, China
    2. Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi'an 710127, China
    3. Institute of Earth Environment, CAS, Xi'an 710075, China
  • Received:2022-01-20 Revised:2022-03-16 Online:2022-08-28 Published:2022-10-25
  • Contact: ZHA Xiaochun E-mail:wn072701@163.com;zhaxch@snnu.edu.cn
  • Supported by:
    National Natural Science Foundation of China(41971116);National Natural Science Foundation of China(41801060);The Fundamental Research Funds for the Central Universities(2020TS102)

Abstract:

Through extensive and detailed field investigation inside and outside the Zoige Basin in eastern Tibet Plateau, a typical sedimentary profile containing the stratigraphic sequence of paleolake facies and paleo-riverbed floodplain facies was found in the front of the second terrace of the Yellow River in the Maqu section at the outlet of the Zoige Basin. Through grain size characteristic analysis and Optically Stimulated Luminescence(OSL) dating, we found that: 1) The pale-blue-grey paleolake sedimentary layer in the profile indicates that the lacustrine sediment formed in the deep-water anoxic environment, while the mottled pebble layer covered by the pale-yellow-orange lenticular sand layer was a typical fluvial floodplain sediment, which indicates the process of strong dynamic flow. The unconformable contact relationship between the two layers indicates that the profile is a typical sedimentary evidence for studying the Zoige Basin dissected by the Yellow River. 2) The OSL dating results of the top boundary of the pale-blue-gray paleolake sedimentary layer and the bottom boundary of the paleoshore-shallow lake sedimentary layer show that the Yellow River dissected the Zoige Basin at 37 ka BP, resulting in the leakage of lake water. At 35 ka BP, the lake water became shallow and disappeared, and then the Yellow River connected the water system of the Zoige Basin. 3) The strong neotectonic movement of the East Kunlun fault in late Pleistocene and the warm and humid climate of the Tibet Plateau in 37 ka resulted in the aggravation of the headward erosion of the paleo-Yellow River source in the rift valley grassland, and the Zoige Basin was dissected by the paleo-Yellow River from the west to the east in the Maqu bottleneck reach, resulting in the discharge of the paleolake water through the Yellow River, thus connecting the water system of the Zoige Basin and making it the source of the Yellow River. The study results have important scientific significance for an in-depth understanding of the evolution of river-lake water system and the formation of Yellow River water system in northeastern Tibet Plateau.

Key words: sedimentary evidence, OSL dating, headward erosion, Yellow River, Zoige Basin