PROGRESS IN GEOGRAPHY ›› 2020, Vol. 39 ›› Issue (8): 1319-1332.doi: 10.18306/dlkxjz.2020.08.007

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Prehistoric catastrophic surface processes and their impacts in the Guanting Basin, Qinghai Province

RONG Xiaoqing1(), PANG Jiangli1,*(), HUANG Chunchang1, ZHOU Yali1, WANG Zhaoduo1, ZHANG Yuzhu2, GUO Yongqiang3, ZHAO Hui1, CHUI Yuda1   

  1. 1. School of Geography and Tourism, Shaanxi Normal University, Xi'an 710062, China
    2. College of Urban and Environmental Sciences, Northwest University, Xi'an 710127, China
    3. Institute of Mountain Hazards and Environment, CAS, Chengdu 610041, China
  • Received:2019-06-13 Revised:2019-09-26 Online:2020-08-28 Published:2020-10-28
  • Contact: PANG Jiangli E-mail:xiaoqing_rong816@163.com;jlpang@snnu.edu.cn
  • Supported by:
    National Natural Science Foundation of China(41771110);National Natural Science Foundation of China(41971116);National Natural Science Foundation of China(41801060)

Abstract:

This study conducted field investigations in the Guanting Basin of the north shore of the Yellow River. A Holocene complete soil profile was identified over the Erfangcun Ruins, which is situated to the east side of the Lajia Ruins and has preserved multiple records of the information of aeolian loess and palaeosol and evolution of land resources, catastrophic surface processes, and human activities during the period of the Xindian culture. Sediment samples were taken from the profile systematically on the basis of field pedo-sedimentological observation. We established the basic pedo-stratigraphic sequence by using optically-stimulated luminescence (OSL) dating and physicochemical indices. The stratigraphic sequence of the Erfangcun profile from the top to the bottom is listed as modern soil (MS)-late Holocene aeolian loess (L0)-Middle Holocene palaeosol (S0)-early Holocene transitional aeolian (Lt). The most significant feature of this sequence is that the deposit of flashfloods and mudflows with a thickness of 1.2-1.5 m have split the Chernozem soil into two sublayers, which was the result of the catastrophic land surface processes and the climatic and environment changes. Optically-stimulated luminescence dating results suggest that enormous flashfloods and mudflows burst out during OSL age 3940-3780 a, equivalent to14C age 3850-3600a BP. They ran over the valley and deposited in the front of the paleo-alluvial-pluvial fans of the second terrace of the Yellow River. The deposit of the flows was covered by the ashes of the Xindian culture (3600-3400 a BP). The barren land formed by the flashfloods and mudflows caused the decline of agriculture and gave birth to stockbreeding. This soil layer is in sharp contrast to the fertile and loose soil during the period of the Qijia culture (4150-3850 a BP). Overall, the results of the study revealed that prehistoric human agricultural land use pattern in the area of the Lajia and Erfangcun Ruins in the Guanting Basin was changed by the degradation of soil caused by the catastrophic floods and climate change. It may have implications for further insights into prehistoric land use and the changes of environment in the transitional area of the Tibet Plateau and the Loess Plateau.

Key words: prehistoric culture, Ustic Luvisol, land resources, natural disaster, Guanting Basin