Evolution of millennial-scale sandy land’s advance and retreat in the Chinese sand-loess belt since 150 ka

Understanding the evolution of aeolian activities and the changes in desert/sand environments is crucial for clarifying their occurrence mechanisms and promoting ecological restoration. Although evidence from loess and lake records in the Chinese sand-loess belt has shown the role of the East Asian winter monsoon (EAWM) in duststorm activities, these records can’t clearly divide the intensity grades and shifts in material components nor explain the mechanism. This study used grain size, magnetic susceptibility (MS), and the SiO₂/Al₂O₃ ratio analyses, along with the grain size end-member (EM) model, fractal dimension (Dv), and MS-based paleo-precipitation reconstruction to clarify these aspects. Four grain size end-members (EMs) revealed that fine grains were predominantly derived from westerly wind and pedogenesis, while the EAWM primarily transported coarse grains. We classified aeolian activity intensity into three grades based on changes in the proportion of sand, which were the main signs of intense wind erosion in the LHG profile located in the southeastern margin of the Mu Us Sandy Land (MUSL). Since 150 ka, there have been three major episodes of sand expansion and three fixed or shrinking intervals. It was mostly a sand environment, except during the early L₁F phase when it became a typical desert environment with mean annual precipitation (MAP) of 164.49 mm. Desert/sand evolution was constrained by moisture, vegetation, and wind field conditions. These factors were driven jointly by solar insolation and ice sheet dynamics, and synchronized recorded glacial-interglacial and millennial-scale oscillations. The findings help improve our knowledge of regional ecological environment changes and aeolian disaster monitoring and prevention.