Holocene lake-level changes of Hurleg Lake on northeastern Qinghai-Tibetan Plateau and possible forcing mechanism

The palaeoshorelines of a lake are the direct geomorphic evidences to reflect past water levels and record information on palaeoclimatic changes. Previous research indicates that the timing and forcing mechanisms of climatic change on the northeastern Qinghai-Tibetan Plateau (NE QTP) are still controversial. Here, we report quartz optically stimulated luminescence (OSL) ages for beach deposits and accelerator mass spectrometry (AMS) C-14 age for plant remains, shoreline features and geomorphic exposures that contribute to a reconstruction of the lake-level history of Hurleg Lake on the NE QTP. The results imply that (1) three high lake levels are dated to 6.8-6.4, 5.0-4.7 and 2.2-1.4 kyr, corresponding to relatively wet and stable climate from pollen records of sediment core in this lake during mid-late Holocene; (2) the highest lake-level period occurred at 5.0-4.7 kyr, which is almost synchronous with the highest effective moisture phase from synthesized lake records influenced by the Westerlies and (3) no beach deposits around Hurleg Lake and lower lacustrine deposits in Toson Lake were found during early Holocene, suggesting lower lake level of Hurleg Lake in this period. These results might imply that the Westerlies and local topography rather than Asian summer monsoon dominate the moisture availability in this region during the Holocene.