LAKE LEVEL RECONSTRUCTION OF HUANGQIHAI LAKE IN NORTHERN CHINA SINCE MIS 3 BASED ON PULSED OPTICALLY STIMULATED LUMINESCENCE DATING

Huangqihai Lake is an inland terminal lake, located at the East Asian summer monsoon (EASM) marginal area in semi- arid northern China. The lake level fluctuations sensitively reflect the moisture availability in the catchment that is regulated mainly by EASM precipitation. The aim of this study is focused on the reconstruction of lake level changes during the last glacial period and Holocene based on a sedimentological approach and optically stimulated luminescence dating. Five outcrops around the lake were identified and sampled during the field work. The pulsed OSL (POSL) dating technique is applied, owing to chemically irremovable feldspar contamination of quartz in most of the samples. The luminescence characteristics of POSL signals are systematically checked. Accelerator mass spectrometry (AMS) ¹⁴C dating is used to date four samples (charcoals and animal bones) collected from one section.

The chronological and geological evidences demonstrate that the water level of Huangqihai Lake reached a peak during ~10−8 ka and lowered toward the middle and late Holocene, indicating the highest regional effective moisture occurred at the early Holocene. This pattern is broadly coincided with the peak of East Asian monsoon intensity according to the stalagmite ¹⁸O isotope from the monsoon influenced southern China; but is out of phase with other lake records in adjacent area. Between ~50 and ~11 ka, aeolian and fluvial deposition prevailed around the lake basin and no lake sediment was found above 1277m (~14m a.p.l.l.), demonstrating a low lake level during this interval (compared with that of the early Holocene), which contradicts the extensively reported “MIS 3a mega-lake” event over the Tibetan Plateau and desert regions in north China.