Multistage responses of Aeolian red clay provenance changes to quaternary aridification and monsoon circulation evolution in southern China

As a subtropical response to Late Cenozoic global cooling and the evolving East Asian monsoon circulation at different stages, the provenance changes of Quaternary red clay (QRC) and its overlying aeolian loess are key to accurately interpreting large-scale atmospheric circulation patterns and the expansion of aridity in the Asian interior. However, the source-to-sink model and orbital-scale evolution of QRC have long been controversial and lack quantitative constraints. In this study, based on extensive detrital zircon U Pb dating of the LX QRC profile in the western Dongting Basin and the potential source region, the quantitative provenance modeling were performed. The Mid-Pleistocene Transition strengthened East Asian winter monsoon (EAWM) driven aeolian accretion, but a strong East Asian summer monsoon (EASM) intensified proximal erosion, with strongly-vermiculated clay dominated by Lishui River(55.79%) and Yangtze River (31.68%), and minor Chinese Loess Plateau (CLP) (12.52%). The Mid-Brunhes Event brought stronger interglacial EASM and larger amplitude, enhancing interglacial erosion and glacial exposure of Lishui River, yielding weakly-vermiculated clay dominated by Lishui River (80.85%). In the late Quaternary, accelerated cooling, stronger EAWM and aridity, and retreating EASM led to binary Yangtze River (57.28%) and CLP (41.18%) loess input. This study confirms that changes in aeolian provenance do not simply equate to a linear progression of aridity in the Asian interior. Under the asymmetric coupling of global climatic background and East Asian monsoon circulation, humid subtropical regions can trigger complex multistage responses of terrestrial aeolian sediment provenance to aridification processes through changes in regional surface processes.