Cosmogenic 10Be inferred lake-level changes in Sumxi Co basin, Western Tibet

Most Tibetan lakes are surrounded by conspicuous regressive shorelines attesting to high-water levels in the past. Concentrations of the in situ produced cosmogenic radionuclide 10Be in bedrock from the three highest terraces surrounding Sumxi Co, situated in Western Kunlun, indicate that the highest lake-level appeared before 10,000–11,500 yr, and most likely between 11,000 and 12,800 yr. Younger ages for the two lower terraces imply regression of Sumxi Co during the early-mid Holocene. The concurrency of the highest lake-level with orbitally induced maximum northern hemisphere summer insolation suggests that the increase in water supply to Sumxi Co was most likely associated with increased recharge from melting glaciers. We conclude that the enhanced Indian monsoon during the early Holocene did not penetrate the Tibetan plateau and affect the northwestern part of Tibet significantly.