Luminescence dating of sandy loess along the middle Yellow River and its implications for aeolian–fluvial interactions

Differing from the classic fine silt-dominated loess on the southern and central Chinese Loess Plateau (CLP), sandy loess is extensively distributed along the southern bank of the middle Yellow River and reaches thickness of up to ∼ 200 m. However, its deposition time and formation processes remain unclear. In this study, we dated three representative sandy loess sections along the middle Yellow River using single-aliquot regenerative-dose optically stimulated luminescence (OSL) and multiple-aliquot regenerative-dose recuperated OSL (ReOSL) dating protocols on fine quartz grains (4–11 μm). The reliability of these methods was robustly verified through traditional luminescence dating checks. Our dating results showed that the sandy loess was predominantly deposited during the last glacial period and exhibited an exceptionally high dust accumulation rate surpassing that of the classic loess on the southern and central CLP. By considering atmospheric circulation, geomorphology, and proxy data from both the sandy loess and the Yellow River fluvial sediments, we propose that the sandy loess primarily originated from the proximal riverbeds and fluvial plains of the middle Yellow River, transported by northerly East Asian winter monsoon (EAWM) winds. During the last glacial period, weakened East Asian summer monsoon (EASM) in central and northern China resulted in reduced runoff and vegetation cover in the middle Yellow River region. Consequently, the riverbeds and fluvial plains served as main sources of dust material. Subsequently, the strengthened EAWM winds carried and deposited the dust along the southern bank of the middle Yellow River, culminating in the formation of the sandy loess. Our study underscores the importance of aeolian and fluvial processes interactions in contributing to the formation of the sandy loess along the middle Yellow River and suggests that the investigated sandy loess holds potential for high-resolution paleoclimate reconstruction.