Multi-index, High-resolution Stalagmite Records Research During MIS9/8 In Chongqing Shuiming Cave, China

Many research results of geologic record showed that, the most prominent feature in the quaternary is the existence of periodic climate glacial-interglacial cycles.And the change of climate which occurred in the periods of glacial and interglacial attracted more attention from domestic and foreign scholars.the great range of summer monsoon precipitation caused by sharp climate change will lead to seriously damage to the development of the society and the ecological environments of the monsoon region,which is living the population of nearly two-thirds of the world.Therefore,it’s the major task that improve the skills of forecasting change of climate and environment and work out the strategy which benefit the development of society and economy.However,if we want to improve the skill of forecast the climate change, depending on the carrier which record high-resolution information to research the change and variability of past climate is a important path.Further,we can find out the rules, boundary conditions and the response mechanism of past climate, understand the process of climate change and the response mechanism of human action and realize the trend of climate changing exactly, meanwhile, providing scientific basis for planning of responding to environment changes.This paper is based on Chongqing Fengdu as the study area,where is affected by the monsoon primarily.We use the 25 ²³⁰Th dating data and 430 stable oxygen and carbon isotope data of Stalagmite from Shuiming Cave in Fengdu area established stalagmite oxygen and carbon isotope time series of high resolution during BP268.47ka³32.94 kaBP,combined with other stalagmite record which is belongs to Yangtze River basin,we analysis the internal characteristics of climate during the MIS9^MIS8,Comparing the summer insolation for 65°N,ice core record,North Atlantic SST and using power spectrum analysis to further analysis the possible driving mechanism of the Asian monsoon climate changes.The result of Ca, Mg, Sr, Ba from the stalagmites SMY1 tested by ICP-MS/OES and stable carbon and oxygen isotope analysis date are compared,on the basis of which we discussed the controlling factors and climatic significance of the trace elements from the stalagmites SMY1,Conclusions are drawn as follows:（1）The results of the stalagmites stable oxygen show that:compared with the stalagmites LZ15 from Linzhu cave in the Hubei province, they present similar trends, which prove SMY1 stalagmite record is dependable.The curve of δ¹⁸O from Stalagmites SMY1 is similar to the curve of 65 °N solar radiation.The overall curve show obviously in form of “three crests and four valleys”,which prove the monsoon climate sensitively response to changes solar radiation energy in long time scales.And this result support the statement that the monsoons change is directly response to the monsoon was affected little by ice changing in high latitude in trace scale, however, responded to solar radiation. meantime, oceanic temperature gradient, water transport route and topographic change are all important elements cause the change of stalagmites δ¹⁸O.（2）The δ¹⁸O in SMY1 obviously showed 5 sub-stages and period during MIS9, there are 3 interglacial:stages:9a=277. 84²96.58 kaBP, 9c=303.30³15.10 kaBP, 9e=321.54³32.94 kaBP, 9c is the strongest monsoon session in this study.There are 2 Glacial stages:9b=296.58³03.30 kaBP and 9d=315.10³21.54kaBP;Comparing ice core with SST record,the δ¹⁸O recorded millennial-scale event exactly.The δ¹⁸O record showed a millennial-scale warm event appeared before MIS9/8 transition,in which monsoon was stronger and climate warmer. After of this,climate turned rapidly to dry and cold,and monsoon turned to weak.Through the comparative analysis with CH₄ and SB61-O records,we proposed that the time of transition of MIS9/8 was 278²81kaBP.（3）In MIS9/8 transition, the stalagmite SMY1 δ¹³C ranges from-2.94‰ to 9.6‰, fluctuation on reached 5.7‰,average value was-6.51‰.The transformational process of glacial-interglacial climate transition can be recorded into stalagmite by outside vegetation environment.On orbital-scale,δ¹³C can serve as the geological record target to reflect the surface vegetation changes.In the transit process of cold/warm,glacial/interglacial climate,stalagmite δ¹³C was mainly affected by produced rate of soil CO₂ which is more sensitive to temperature;The REDFIT38 power spectrum analysis of stalagmite SMY1 δ¹³C showed that the north Atlantic thermohaline circulation and the solar activity play an important role in monsoon climate in millennial-scale.（4）The Sr/Ca ratio of SMY1 ranges from 40×10-6 to 228×10-6,the Ba/Ca from 89×10-6 to 485×10-6and Mg/Ca from 0.02×10-6 to 0.04×10-6.the comparative analysis with δ¹³C records showed that,Mg/Ca were positively correlated with δ¹³C records.Temperature is the main controlling factor of gradually-decreased Mg/Ca ratio from interglacial MIS9 to glacial MIS8.Ratios of Sr/Ca and Ba/Ca present positive correlation,but both of them have obvious negative relation with the Mg/Ca ratio.It indicated that the formatted mechanism were similar,but were different from the Mg/Ca ratio.Atmospheric dust activity,overlying bedrock and soil could be the important factors that affected Sr/Ca,Ba/Ca ratios to change.At the same time, the modern monitoring,the positive correlation of Sr/Ca,Ba/Ca ratios and stalagmites SMY1 δ¹⁸O showed that,the ratios of two elements may be controlled by PCP and dilution of participation.