地质科技通报 (Nov 2023)

Sedimentary evolution revealed by aeolian and lacustrine depositions in the southern margin of the Weihe Basin during the Early Pleistocene

  • Ting Wang,
  • Hang Zhang,
  • Youbin Sun

DOI
https://doi.org/10.19509/j.cnki.dzkq.tb20220111
Journal volume & issue
Vol. 42, no. 6
pp. 95 – 105

Abstract

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The Quaternary climate is characterized by a notable cooling and significant glacial-interglacial fluctuations driven by the influence of orbital-induced insolation and bipolar ice-volume variability. The Weihe Basin, located in the critical zone of the Asian monsoon region, accumulated thick fluvial-lacustrine deposition and aeolian deposition since the Cenozoic, which is a key placeto explore the environmental evolution during the Quaternary period. Objective The fluvial-lacustrine strata of the Sanmen Formation in the Weihe Basin are considered to be closely related to Palaeo-Sanmen Lake. However, the relationship among the stratigraphic age of the Sanmen Formation, the evolution of the palaeolake as well as the evolution of regional tectonics is still under much debated. Methods In this work, the magnetic susceptibility and grain size records from two sections (Yanyu and Wujiabu) in the southern margin of the Weihe Basin have been generated to investigate sedimentary evolution during the interval of 2.6-1.6 Ma. Results The mean grain size (MGS) and magnetic susceptibility (MS) of the Yanyu loess exhibit large-amplitude variations as proxies for the East Asian winter and summer monsoons. The MGS and MS variations in theWujiabu section show that lithology changes from lacustrine to aeolian facies occurred at 1.95 Ma in the southern margin of the Weihe Basin. In lacustrine environments, MGS is positively correlated with MS and is sensitive to fluctuations in lake level linked with monsoonal precipitation. Conclusion Overall, the climatic characteristics on the margin of the Weihe Basin during the early Pleistocene can be divided into two intervals: ① the lake level frequently fluctuated during 2.6-1.95 Ma, ② the lake shrank from 1.95 to 1.6 Ma. We suggest that the disappearance of Palaeo-Sanmen Lake was affected by the development and integration of the Yellow River.

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