Timing of Late Quaternary palaeolake evolution in Tengger Desert of northern China and its possible forcing mechanisms

摘要

Palaeolake evolution history has been used to reconstruct the Late Quaternary environmental and climatic conditions in East Asian monsoon area. In this study, based on the OSL chronology (33 samples) and the stratigraphy of shorelines or lacustrine sequences, we reconstructed the Late Quaternary evolution history of the Zhuyeze palaeolake surrounded by the Tengger Desert at the northern edge of East Asian summer monsoon. The luminescence dating results with geomorphologic analysis indicate that: (1) contrary to previous interpretations on MIS 3 mega-lake derived from ~(14)C chronology, highstands of ca. 30 m above modern playa are OSL dated to around 90-80 ka (MIS 5a), and no evidence of MIS 3 highstands has been found, which questions the previous climate pattern of 'uniquely warm and wet Late MIS 3' in northwestern China. The high insolation at MIS 5a triggered the strengthened summer monsoon which brought more rainfall to the study area, causing the highstand in Zhuyeze; (2) a substantial lake with a water level of ca. 20 m above the modern playa was present during 8.0-5.0 ka (Mid-Holocene), indicating that the wettest stage of the Hol-ocene occurred in the Mid-Holocene. This reconstructed moisture pattern based on lake levels in East Asian monsoon marginal area is out of phase with that in monsoon core area, and we propose that this is possibly related to low sea level during the Early Holocene leading to the study area out of East Asian monsoon influence; (3) the shrinking process of Zhuyeze Lake since 5.0 ka indicate the drying trend during the Late Holocene, responding directly to the changes of the East Asian monsoon triggered by summer insolation at low latitude areas.