OSL dating of a mega-dune in the eastern Lake Qinghai basin (northeastern Tibetan Plateau) and its implications for Holocene aeolian activities

Aeolian sediments are widely distributed in the Lake Qinghai basin of the northeastern Tibetan Plateau (TP), but the history of aeolian activities in the basin is indistinct, and the underlying impacting factors are still poorly understood. In this study, depositional history of a mega-dune from the eastern Lake Qinghai basin was determined by optically stimulated luminescence (OSL) dating. The results show that nearly 30 m thick of sands accumulated during the interval of 7.6 ka, followed by soil formation during the last similar to 5 ka. Together with previously published OSL ages of aeolian sediments, the Holocene aeolian activity in the Lake Qinghai basin was reconstructed as following: (1) The temporary aeolian activity appears to be characterized with a pattern of strengthened intensity during the first half of Holocene but relatively lowered intensity with a gradual decreasing trend afterward; (2) The interval of 7-6 ka in the middle Holocene witnessed a transition from dune activation towards stabilization; (3) A very low sand accumulation rate during the period of 5-3 ka and the contemporaneous extensive palaeosol development imply the least aeolian activity at that period. We inferred that the Holocene aeolian activity in the Lake Qinghai basin was mainly controlled by sediment supply, which was in turn modulated by the lake-level change of Lake Qinghai. Large amounts of sand were available, when the lake level dropped and then beach sands could exposure for deflation.