Dunefield expansion and paleoclimate during MIS 3 in the Qaidam Basin, Northeastern Tibetan Plateau: Evidence from Aeolian-Fluvial processes and revised luminescence chronologies

It is proposed that an extremely warm, humid climate existed in the Tibetan Plateau (TP), including the currently hyper-arid Qaidam Basin (QB), during Marine isotope stage 3 (MIS 3). A detailed luminescence study of aeolian, fluvial and aeolian-fluvial records from the Tiekui Dunefield (TKD) and its margins in the eastern QB reveals paleoenvironmental and paleoclimatic changes during the MIS 3 (ca. 60–32 ka). The records, dated by post-Infrared Infrared Stimulated Luminescence (pIRIR), provide the first aeolian MIS 3 ages in the QB thanks to preservation by overlaying fluvial deposition in the dunefield margins and demonstrate the aeolian expansion of the TKD compared to its modern extent. Complemented by aeolian records in nearby regions, these deposits reflect intensified dune activity in an arid and windy climate and with adequate glacier-derived alluvial-dominated sand supply. These results do not support a significant increase in precipitation from the Asian Summer Monsoon (ASM). Comparisons of new ages derived from pIRIR and Optically Stimulated Luminescence (OSL) of quartz in this study suggest that some published quartz OSL ages of the QB may be underestimated, even below 90 Gy (ca. 30 ka, with normal dose rates of 2.8 Gy/ka). The revised chronology questions previously suggested hypotheses of the existence of a mega Qaidam Lake in the upwind reaches of the basin, under an extremely strong ASM during the MIS 3. We propose a conceptual aeolian-fluvial geomorphic model that demonstrates the paleoclimatic value of aeolian-fluvial records and where and how fluvial process can erode or preserve ancient and previously untapped aeolian records.