Luminescence chronology and paleoenvironmental significance of coastal paleo-red sandy deposits in South China

Late Quaternary coastal red sandy deposits, known as Old Red Sand (ORS), are widely distributed along the southeastern coast of China and provide important archives of past sea-level change, monsoon variability, and coastal aeolian processes. However, their chronostratigraphic framework and environmental controls remain debated. Here we present new quartz optically stimulated luminescence (OSL) ages from an ORS profile on Hainan Island and integrate a comprehensive compilation of published chronological data to reassess regional spatiotemporal patterns and driving mechanisms of ORS development. The new OSL results indicate that aeolian deposition at the studied site occurred mainly during the Last Glacial Maximum (LGM). Regional synthesis reveals two principal ORS accumulation phases at 62–49 ka and 27–14 ka, and demonstrates pronounced spatiotemporal variations between Fujian and South China. In Fujian, major ORS formation occurred when sea level was above −60 m, whereas in South China it was concentrated during MIS 2 lowstands. We propose a conceptual model in which glacial–interglacial sea-level fluctuations regulate coastal geomorphology, sediment availability, and the effectiveness of East Asian Winter Monsoon–driven aeolian transport. A critical −60 m sea-level threshold associated with the Taiwan Strait helps explain contrasting regional responses. These results highlight how regional geomorphic boundary conditions modulate the expression of global sea-level and climate forcing in coastal aeolian systems.