East Asian winter monsoon during the late quaternary shifted the provenance of red earth in mid-subtropical China

Abstract

The loess-like Quaternary red clay (QRC) covers extensive areas in South China, making its genesis and provenance essential for interpreting this unique paleoclimate archive in subtropical regions. However, it remains unclear whether the loess-like QRC originates from local fluvial deposits, the Chinese Loess Plateau, or a mixture of both. This study investigates the provenance of the loess-like QRC in mid-subtropical China, focusing on the interaction between local and distant dust sources. To achieve this, we applied geochemical methods, including grain size analysis, mineralogy, provenance indicators, and quantitative analysis, to two loess-like QRC sections (JL and LHH). Our findings indicate that the silt fraction is more effective for provenance discrimination, necessitating caution when interpreting bulk samples. Notably, the LHH section shows a shift from a predominance of local dust at the bottom to a significantly higher contribution from distant dust at the top. This trend suggests that since around 0.44 Ma, the intensification of the East Asian Winter Monsoon (EAWM) has facilitated enhanced dust transport from Central Asia, shifting the provenance of red earth in mid-subtropical China and reinforcing the mixed-source origin of the loess-like QRC. Additionally, variations in heavy mineral content indicate weak silicate weathering and/or pedogenesis in the YBS and VYS layers, which also suggesting a dry and cold climate since 0.44 Ma. This research provides valuable insights into the sediment dynamics and climatic factors shaping the provenance of the loess-like QRC in subtropical regions.