| Controversy exists regarding the pattern of climate change since the last interglacial in the monsoonal regions in northern China. Some proposed that, within the Holocene, the climate in the mid Holocene was continuously warm and wet (Holocene Optimum) at the northern limit of modern Asian monsoon, while others recently argued that a dry mid Holocene existed during ~7-5 ka in these areas. Conflict also exists in the chronologies of high lake levels before the Holocene. High lake levels indicate humid climate conditions. Some researchers reported that the lakes experienced their high lake levels during Marine Oxygen-isotope stage 3 (MIS 3),whose chronology were mostly based on 14C dating. However, in recent years others reported that the lake levels during Marine Oxygen-isotope stage 5 (MIS 5) were higher than MIS 3 according to the new developed dating methods, such as Optically Stimulated Luminescence (OSL), Electron Spinning Resonance (ESR), and so on.The terminal Huangqihai Lake is located at the northern margin of the present limit of the East Asian summer monsoon, and its evolution is sensitive to monsoon climate changes. In the present study, OSL dating was employed to establish the chronology of lake level changes of Huangqihai Lake since the last interglacial. The single aliquot regenerative-dose (SAR) protocol was applied to both quartz and feldspars. Based on OSL ages, sedimentology and other proxy data (grain size, chemical element), we conclude that(1) The SAR protocol and the standardized growth curve (SGC) method are appropriate for De determination for lake deposits of Huangqihai Lake. The SGC was existed and didn't show saturation up to a dose of 600 Gy, which potentally allows the dating of much older samples. The Des determined by the SGC are in agreement with the Des by the SAR protocol for Holocene samples. Due to the feldspar contamination, the quartz OSL ages of some old samples (De>300 Gy) should be considered as minimum ages.(2) The De determined using feldspar is obviously underestimated. The extent of underestimation was systematically increased with the increase of De. Infrared stimulated luminescence (IRSL) De underestimation up to ~36% is observed for a sample with an expected age of ~34 ka. However, the anomalous fading of feldspars show little impact on younger samples (less than 1 ka). Higher preheat and stimulation temperatures (320oC preheat and 300oC stimulation temperature) can obviously reduce the anomalous fading effect, but couldn't remove it.(3) The altitude of the highest lake terrace in Huangqihai Lake is ~1374 m asl (~106 m above the present lake level), well above 1340 m asl (~72 m above the present lake level) that was detected by previous researchers. The OSL ages show that the highest lake levels were occurred during MIS 5. The lake level was then continuously declined to 1274 m asl (~6 m above the present lake level) until MIS 3. No evidence showed that the lake has experienced higher lake level during MIS 3.(4) Based on OSL chronology, grain size,element analysis and sedimentology, (1) since the last deglaciation the lake level began to rise up and reached 1340m a.s.l.. The climate during the early to mid-Holocene (from 11.4±1.0 to 7.4±0.7 ka) was humid and resulted in a high lake level, marked by the accumulation of deep lake sediments, and the lake level showed a slightly decline in this stage. (2) The lake level significantly declined between 8.7±0.8 ka and 6.7±0.7 ka, implying that some severe drought events occurred during this period, and that the climate was dryer after 6.7±0.7 ka compared with that before. (3) The mid to late Holocene (from 7.4±0.7 ka to 2.2±0.2 ka) had an increasingly arid climate which resulted in the accumulation of shallow lake sediments, characterized by coarser grain size and low element content. (4) Two abrupt dry events were detected by both grain size and element content during this period. (5) The dry climate persisted since 0.93±0.07 ka is indicated by fluvial deposits.
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