The Paleoclimatic Event During MIS3Period(Ranging From51.3Ka BP To37.8ka BP)Recorded By The Stalagmite In Chongqing Yangkou Cave

Nowadays, the stalagmite has been one of the most concerned paleoclimatic information in geoscience field which follows the study of marine sediment, ice-core, lake, and loess. Thanks to its high resolution, possibility to extract rich information parameter, and long time span, it has an irreplaceable advantage in restoring paleoclimate and environmental changes in both interannual and seasonal time-scale overweighted other geologic records. The paleoclimate research by studying the speleothem record has been launched all over the world. And it achieved fruitful research findings in both theory and application. This essay is guided by earth system science and based on the sensibility of karstification to environment to extract environmental information recorded by spelethems. From the analysis of stable isotope climatic and environmental proxy, the paleoclimate ranging from51.3ka BP to37.8ka BP in Chongqing and adjacent region is interpreted by multi-proxy and represents the changing process of environment.The JFYK7, from Chongqing Jinfo cave, is the the research object. By means of the high-resolution TIMS-U dating and hydrogen and oxygen isotope record, the paleoclimate changing time sequence, earlier period of MIS3(from51.3ka BP to37.8ka BP), which is in high resolution, is established to reveal the regularity of climate change in this region, discuss the mutual influence of eastern Asia Monsoon and southwest Monsoon and their evolving pattern, and provide scientific foundation for sustainable development in western regions and for comparison of global karst ecology system.This essay is studying on a section which is24.1cm from the top, which contains large amount of uranium ranging from5.8ppm-12.4ppm, mean value10ppm, and acquire9high-resolution dating data with mean deviation±161a.Based on high-resolution time sequence, use477pairs of hydrogen and oxygen isotope data to established early period of marine oxygen isotope stage3(MIS3)51.3～37.8ka BP, the evolving time patter of East Asian summer monsoon. In growing period,δ18O value of JFYK7stalagmite ranges from-5.96‰～9.47%o, the amplitude3.5%o. Compared with the δ18O value of the stalagmites in the corresponding time in Guangxi and Guizhou caves, the δ18O value of JFYK7stalagmite is generally light and negative, however it is positive-3%o than XBL-1stalagmite from Yunnan Xiaobailong cave which proves the influence of southwest monsoon overweight southeast monsoon in Chongqing. With six apparently identified events of positive δ18O value and six negative ones, the overall curve shows in form of "six crests and valleys". According to the characters of beginning date of DO event, lasting span, and amplitude of Greenland ice-core record as well as the relationship with H event, H event (H4å'ŒH5) and DO event (DO8～13) of the stalagmite are marked. The regional comparison indicates that δ18O value of the stalagmites from Yangkou cave,Yongxing cave and Hulu cave mean the components of monsoon precipitation are of great similarities. The comparison of high and low latitude indicates the crest and valley in thousand-year scale completely correspond, and so does the crest and valley of δ18O value of Dansgaard Oeschger (DO event), which reflects the vapor transmission ability of ITCZ and its average location changes greatly influence on east Asia monsoon and northern and southern high latitude region.The occurrences of H4and H5event are different in different geologic records. The greater difference of H event is given by different materials in earlier time. The same kind of stalagmite record Hulu MSL, XBL-1from Yunnan Xiaobailong cave and YX51from Yongxing cave all suggest the coldest H4event happened in39.3ka BP, while the higher resolution JFYK7stalagmite record in39.2ka BP within the dating deviation almost the same. Two dating point of H5event is of higher resolution which vertifies the marking H5event in48.1Ka BP is more precise.According to the research on how the carbon isotope migrate through vegetation-soil-bed rock-cave drip process, we know that813C gradually gather during its migrating through vegetation-soil-cave drip process and the non climate information like the dissolution of bed rock, has little to do with the carbon isotope in the stalagmite sediments. The modern observation further verifies that under the conditions the carbon isotope in the cave sediments can be an efficient way to reflect the variation of the caves’ vegetation. The combination of oxygen isotope information indicate that during the strong period of monsoon,δ13C of the stalagmite mainly affect the climate change through corrosion effect; while during the weak period of monsoon,δ13C mainly reflect C3/C4vegetation’s abundance variation.The variation of solar radiation within orbit, as the driving force of the Earth’s climate, plays an important role in the climate’s variation. The occurance and intensity of the East Asia monsoon climate directly affect the solar radiation at65°N, which indicates that the time and intensity of the East Asia monsoon climate may has nothing to do with the variation of the ice capacity of the Northern Hemisphere. Meanwhile, power spectrum analysis has already explained that carbon isotope respectively existed in the period of2273and4500, which has something to do with the1470period of DO cycle and the1500period of global oceanic mixing rate, and this can indicate that the thermohaline circulation of North Atlantic Ocean may to some degree affect East Asia monsoon climate.