Environmental Significance during Holocene-Late Pleistocene:Evidence from Napahai Lake and Beihai Wetland,Western Yunnan,China

摘要

North India Ocean-South Asia monsoon is one of the most typical environmental driving forces.South Asian monsoon plays an important role in the climate of southern part of China,especially in Yunnan province.High-resolution sediment core records from Tengchong Beihai wetland and Shangri-La Napahai Lake located at the both sides of Gaoligong Mountain in Yunnan,have provided insights into the factors that control the strength of the South Asian monsoon.South Asia monsoon has influence on precipitation of Yunnan area and brings the signal of rapid climate change from the ocean into two places respectively.This paper has reconstructed the local climatic evolution for 57 ka B.P.(before present),through the climatic proxies such as total organic carbon (TOC),magnetic susceptibility,pollen assemblages,δ13 C and grain-size.A comparison was made between two climatic records from the Napahai lake and Beihai wetland.The results show that 57-44 ka B.P.witnesses the decreasing temperature and the increasing humidity; During 44-37 ka B.P.,there is an alternation of wet/cool and wet/warm environment; From 37 ka B.P.to 31 ka B.P.,a swampy environment dominates the area; 32-15 ka B.P.indicates a cold climate,while the predominance of plants suggests much dry weather during this interval; The temperature keeps slightly rising while the humidity decreases,in despite of a r dry/ cool and wet/warm fluctuation during this period of 15-0 ka B.P.Tengchong wetland records summer monsoon signal readily,while Shangri-La Napahai lake is more sensitive to winter monsoon.The former sediment rate is faster than the later one.The overall n-end of our TOC content in Shangri-La suggests that the summer monsoon was modulated by orbitalscale variations in summer insolation 25°N.