Optical dating of sand wedges and ice‐wedge casts from Q inghai L ake area on the northeastern Q inghai‐ T ibetan P lateau and its palaeoenvironmental implications

Sand wedges and ice‐wedge casts in the Q inghai L ake area on the northeastern Q inghai‐ T ibetan P lateau ( QTP ) occur within alluvial gravel or river terrace deposits. In this study, we report the results of quartz Optically Stimulated Luminescence ( OSL ) dating of the infill of five relict sand wedges and one ice‐wedge cast. Combining our dating results with previously published luminescence ages of permafrost wedges in the Q inghai L ake area, we show that sand/ice wedges formed at c.  62 ka, c. 45 ka and between 30 and 15 ka, and that the mean annual air temperature ( MAAT ) was depressed by at least ∼3° C relative to present during the sand/ice‐wedge formation periods. This new work is partially corroborated by post‐ LGM proxy records from lakes and aeolian deposits reported from the northeastern QTP . It also significantly extends the palaeoenvironmental record in the region in the period before the LGM, when other proxy records are rare, allowing a better understanding of the palaeoenvironmental conditions on the northeastern QTP .