The Record of Paleoclimatic Change and the Termination of the Last Interglacial Period From A Stalagmite of Qingxin Cave in South Guizhou

Under the predictive study of the global climate change at present, the dating ages of the high-resolution and the change law revealed by the carbon and oxy ge n isotopic composition from cave stalagmites have made a great contribution for the breakthrough and filling gaps in this field. The high-resolution cl im ate records from 109.00 ka B.P. to 65.90 ka B.P. have been obtained through TIMS -U series dating of 11 samples and carbon and oxygen isotopic analysis of 79 sampl es from No.1 stalagmites in the south part of Guizhou. The No.1 stalagmite began to grow before 109.00 ka B.P. and stopped to grow after 65.90 ka B.P.,its ave rag e growth rate is 4.58mm/100a and is the sediment of the late Pleistocene. The st udy of No.1 stalagmite section in the Qingxin cave reveals that its age and isot ope records can be compared with the oxygen isotopic records of deep-sea cores or sediments at 5a, 5b and 5c phase of Ⅴstage and Ⅳ stage and Lishi Loess beds(L2) in the north of China. The carbon and oxygen isotopic records of stalagmite reveal that these tw o stages between 109.0～102.5 ka B.P. and 86.6～82.0 ka B.P. represented the war m-humid climatic environment and indicated the strong influence of the Asian (Southeast) summer monsoon, the rainfall increased more,the δ 18 O trende d to lowre or negative and the air temperature rose.The stage from 102.5 ka B.P. to 86.6 ka B.P. represented the cold-cool semi-arid and warm-cool humid cli matic envi ronment and indicated that the Asian (Southeast) summer monsoon was gradually weak, the meteoric water was decreased gradually, the δ 18 O was much h e avier, and the air temperature gradually decreased. And the stage from 78.92 ka B.P. t o 65.90 ka B.P. represented the dry-cold climatic environment and indicated tha t t he Asian (Southeast) winter monsoon and the Northwest cold air mass were streng thened, the meteoric water was decreased gradually, the δ 18 O was much hea vier, a nd the air temperature went down quickly,and is the cold beginning period of the last glacial period. In addition, we have determined that the termination point of the last intergla c ial period is 78.92±0.7 ka B.P. ,and this age is the beginning point of the las t glacial period at the same time and can be taken as the boundary age of MIS4/5 according to the precise dating age of TIMS-U series and the records of carbo n and oxygen isotopes from No.1 stalagmite of Qixin cave in Guizhou. The determina tion of the record chronological is not only of stratigraphic significance, but also is chronological significance.