Variation of lake water level recorded by grain sizes of sediments from Hetao Paleolake since 150ka

Based on size data of Bingfanggou lacustrine sedimentation section, which lies in Hetao basin piedmont, combined with chronologic test of ¹⁴C and OSL, the authors comparatively analyzed sediment particle size sensitivity and frequency curve characteris-tics, and made inversion of the lake water level change of Hetao Paleolake since 150ka.The result indicates that the lake water level change of Hetao Paleolake has gone through four stages:① Initial forming stage(150~130ka):Hetao Paleolake was in a shallow lake environment, sediment particle sizes were from coarse to fine, and the water level of the lake was in rising period; ② Developing stage (130~54ka):the lake surface was higher in deep water environment early, sediment particle sizes gradually became thicker and the lake surface declined; ③ Contraction stage (54~18ka):the lake water level dropped rapidly, the fine-grained sediments decreased, and the coarse-grained sediments increased; ④ Demise stage (18ka-now):due to the influence of active faults in piedmont, the Yinshan Mountain uplifted rapidly, the lake atrophied swiftly, the top of the lacustrine strata was covered by diluvial and alluvial materials be-tween the mountains.The main factors controlling the water level change of the paleolake seem to have been the tectonic movement and abrupt change of climate environment.