The Middle Pleistocene Great Lakes period in Otindag Dune Field revealed by optically stimulated luminescence dating

The Otindag Dune Field, located in the northeastern Inner Mongolia Plateau and at the edge of the East Asian monsoon region, is highly sensitive to climate change. However, due to intense wind erosion, preserving sediments that record regional Cenozoic climate changes is challenging, resulting in a gap in long-term climate change research for this region. Six ancient lacustrine sand profiles in the north and west of the sandy land, protected by basalt and calcium carbonate layers, were selected for this study. Both conventional single-aliquot regenerative-dose (SAR) and SAR thermally transferred optically stimulated luminescence (TT-OSL) methods were employed for dating to establish stratigraphic chronological framework. Conventional SAR yielded underestimated OSL ages for lacustrine sands due to signal saturation. In contrast, TT-OSL did not reach saturation during testing, providing a stratigraphic chronological framework for the sandy land extending back to 606 ka, the oldest stratigraphic age obtained thus far in this sandy land using OSL dating. Combined with grain size and quartz grain surface morphology, the middle Pleistocene climate was revealed to have undergone warm-humid (606–480 ka), cold-dry (457–412 ka), warm-humid (400 ka), and cold-dry (290–247 ka) phases. This updates previous records of the Late Quaternary lacustrine phases of the Inner Mongolia Plateau. Based on altitude, landforms, and stratigraphic sediment records, the elevation of paleo-lake surfaces is suggested to have reached 1300 m a.s.l during the late Middle Pleistocene. The spatiotemporal evolution of the lake basin was primarily controlled by regional tectonic uplift, which governed lake migration and the attainment of highstand levels. East Asian monsoon variability acted secondarily to modulate water levels within this tectonically defined framework. • Optically stimulated luminescence dating extends Otindag Dune Field chronology to ∼606 ka. • Lacustrine deposits reveal a paleo-lake level at ∼1300 m a.s.l. in the late Middle Pleistocene. • Tectonic uplift was the primary driver of lake evolution, with climate as a secondary modulator.