Cosmogenic ¹⁰Be surface exposure dating and glacier reconstruction for the Last Glacial Maximum in the Quemuqu Valley, western Nyainqentanglha Mountains, south Tibet

The nature and timing of glaciations enable inferences to be made about glacial climates. However, the paucity of reliable glacial chronologies impedes a full understanding of the Last Glacial Maximum (LGM) climate in the western Nyainqentanglha Mountains, south Tibet. In this study, we investigated the LGM glacial history in the Quemuqu Valley, western Nyainqentanglha, using ¹⁰Be surface exposure dating. We used a physically based glacier model to reconstruct the LGM glacial surfaces, and estimated the LGM equilibrium-line-altitude (ELA) using integrated methods. Combined with previously published ¹⁰Be exposure ages from the western Nyainqentanglha, ten ¹⁰Be exposure ages imply a relatively restricted glacial extent in the LGM but extensive growth in the early last glacial. The modeled LGM glaciers had ice areas of ∼36.3 km², 3.21 km³ in volume and 89 m m in average thickness in the Quemuqu Valley. The reconstructed LGM ELAs have values of 5463–5583 m asl, with a depression of ∼244–364 m. By combining the reconstructed ELAs with an equation deduced from glacier mass balance, we concluded that the temperature dropped by ∼2.6–4.6 °C in the LGM relative to the present, with 30–70% lower precipitation than the present. Global cooling induced the LGM glacial advance in the western Nyainqentanglha despite decreased precipitation.