Isotopic Ages and Paleoclimatic Implications of No．1 Stalagmite from Dongge Cave in Libo

Key words: 
• stalagmite /
• U-series age /
• paleoclimate stable isotope /
• Dongge cave /
• Libo corea

Abstract: Stalagmites in cave is the most comprehensive and systemetic paleo climatic environmental information contaimed in karst records. The study has shown the environmental changes in cave and at outside of the cave with the indication of the different degree in the composition of stalagmite, texture or structure, sediment or growth laminates, bedding plane structure, growth rate and environmental changes of paleo climate and so on. The reconstruction paleoenvironment by use of the preserved information in stalagmite is one of the popular project for lastest the 20 years. Under the study of the global climatic changes, high resolution dating and the change law of carbon and oxygen isotopic component of stalagmites in cave have made a great contribution to the breakthrough in the field. A large stalagmite with continuous profile of clear annual growth laminae for studying the paleoclimatic changes were found in Dongge cave of Libo area last year.Because the laminae of stalagmite is mainly composed of calcite, they are suitable to be measured by TIMS U series method to get reliable and high resolution ages compatable with other materials such as lake or marine sediments. Therefore, stalagimte may have vast vistas for geochronology study since the middle Pleistocene Epoch. Paleoclimatic information from 163.3 ka B.P. to 91.3ka B.P. have been obtained through TIMS U series dating ages and carbon and oxygen isotopic analysis to No.3 stalagmite from Dongge cave in Libo. The ages and the change of oxygen isotopic records in Libo area can compare with theⅤ and the Ⅵ stages of oxygen isotopic records of the deep sea cores(or sediments). The results shown that the records of climatic change from 163.3ka B.P. to 91.3ka B.P. in this period in Libo area underweth from the cold period to warm and humid period. It coincides with the wave motion of the global paleoclimatic change, in the meantime, the climatic change of the region also exist.