Abstract
The middle-Pleistocene Xiashu loess deposit in the lower reaches of the Yangtze River (LRYR), southern China, may yield evidence with significant climatic and environmental significance. However, its provenance remains controversial. In this study, grain size analysis, and quartz grain surface microtextural and morphological observations, enabled comparison of the provenance of loess in the LRYR with those on the Loess Plateau in northern China. The results show that the grain size characteristics of the Xiashu loess do not follow the coarse-fine NW-SE trend in northern China, and the surface microtextures of the quartz grains in the Xiashu loess are distinctly different from those on the Loess Plateau in northern China, indicating that the loess deposits in the two regions have different provenances. The Gobi Desert in inland northwestern China are not considered as the primary provenance of the Xiashu loess. Instead, the adjacent floodplains in the LRYR, the alluvial plains of the Huai River and the Yellow River to the north during glacial periods are suggested as the dominant source materials for the Xiashu loess. Under the background of middle-Pleistocene climate transition (MPT), regional aridity and a strengthened east Asian winter monsoon (driven by global cooling and the rapid uplift of the Tibetan Plateau) were considered as the primary drivers for the development of the Xiashu loess. The sustained eolian loess accumulation represent a regional response of the northern subtropical area of southern China to the MPT global cooling event at around 0.9 Ma.
Highlights
Global climate changes and their regional responses are receiving considerable research attention, with Quaternary climate evolution providing an important focus (Liu, 1985; Pye, 1987; Li et al, 2001a; Li et al, 2018a; Purtill et al, 2019; Westerhold et al, 2020)
Previous studies show that dust from inland NW China can be transported to the sea of Japan (Xiao et al, 1999), and the grain-size frequency curve of XG profile has proved this point, so we suggest that a small amount of dust from the remote Gobi Desert in areas of northwestern China was likely to be transported to the lower reaches of the Yangtze River (LRYR)
Previous studies show that dust from inland of NW China can be transported to the sea of Japan (Xiao et al, 1999), the grain-size frequency curve and the quartz grain microtextures, as well as end-member modeling analysis indicate that the Xiashu loess may contain a certain amount of far-distant materials, so we suggest that nearby-source materials dominate the accumulation of the Xiashu loess, and the dust from the Gobi Desert in inland NW China have played a small role in the accumulation of the Xiashu loess
Summary
Global climate changes and their regional responses are receiving considerable research attention, with Quaternary climate evolution providing an important focus (Liu, 1985; Pye, 1987; Li et al, 2001a; Li et al, 2018a; Purtill et al, 2019; Westerhold et al, 2020). The eolian dust deposited on the continent provides a basis for the reconstruction of environment in China. Such as the thick eolian loess deposit on the Chinese Loess Plateau (CLP) in northern China, which is regarded as a valuable sedimentary archive for Quaternary climate and environment changes. Systematic studies have revealed its sedimentation chronology, provenance, the process causing aridification in Provenance of the Loess Deposit northern China and the evolution of the east Asian monsoon climate (Liu, 1985; An et al, 1990; Guo, 2010; Ding et al, 2019). The development of the eolian Xiashu loess deposit in the LRYR of southern China may yield evidence with significant environmental implications
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