Research Of The High Resolution Records Of Stalagmite Y02for Climate Change Of The60～90ka BP In Chongqing Region

60～90ka BP includes the last interglacial MIS5a stage and last glacial MIS4stage. With the frequent happen of the extreme weather events and a variety of geological disasters in recent year, the predictions of future climate change become more and more important. However, in order to predict future climate accurately,we need a profound understanding and research of past climate changes, particularly with our holocene closest to the last interglacial climate.60～90ka BP is the period of the last interglacial to the last glacial. Whereas, this period also coincided with the most severe volcanic eruption:Toba volcanic eruption, since the Quaternary. Different scholars’research reveal the fact: currently, the relationship between the Toba volcanic eruption and "72ka BP climate event" is still controversial.72ka BP is the boundaryof MIS5a and MIS4. So, in order to know the conversion process and mechanism from interglacial to glacial climate, we have the necessary to in-depth study of this period.Because of it’s accurate dating, high resolution as well as preserving climate information intactly, stalagmites are increasingly used in palaeoclimate reconstruction. This paper selects the Yangzi Cave which located in the Asian monsoon region in Chongqing as the research area. Oxygen isotope, carbon isotope, trace element and U/Th age data of Y02have been used to reconstruct the δ18O value record,δ13C value record and trace element record during60-90ka BP. Combine with others stalagmite records and deep-sea cores records and so on, we will try to reveal the climate change during60～90ka BP meanwhile discuss the relationgship between the Toba volcanic eruption and the "72ka BP weather events" as well as the beginning of the H6event. The results indicate that: (1)The δ18O value of Y02shows that: a. during MIS5b to MIS5a period, the monsoon pattern showed a slow and gradual changes. The monsoon change model, Yangzi Cave stalagmite revealing, is validated by the Shanbao Cave stalagmites’record. The fact suggests that monsoon change process of Chinese southwest region is different to Chinese northwest region,during in the MIS5a to MIS5b period. b.Yangzi Cave’s stalagmites oxygen isotope records show that there are large differences between the D/O events. The D/O events of stalagmite record show the climate varied process is a slowly wet, long time wet, and then quickly drying, but the ice core record shows for rapid warming, slow cooling process. Yangzi Cave stalagmite’s oxygen isotopic records of D/O21event to the D/O20event is a smooth transition process. c.The start time of H6event is classified at60ka BP, but multiple stalagmites’ oxygen isotopic records, including Dongge Cave stalagmite’s oxygen isotopic records, have not record of H6event in60ka BP. Yangzi Cave stalagmite’s oxygen isotopic records show H6events occurred in63-64ka BP and Tian’e Cave stalagmite’s record show H6events occurred in60～63ka BP, so H6event start time should be scheduled at63ka BP. d.Y02Stalagmites’ stable oxygen isotope curve and other stalagmites isotope curve, ice core records exists consistency in the change trend.It reveal the fact that stalagmites oxygen isotopes as the ancient climate change’s proxies is can stand the test. But different stalagmites oxygen isotopic records still exist differences in detail, especially some weather events. Stalagmites’818O records show that it has a lot of shortcomings and reconstruction of climate need a lot of stalagmite records.(2)Yangzi Cave Y02stalagmite’s high-resolution δ13C value record show that: the time of Toba volcanic eruption in Indonesia is about72ka BP. Many research think Toba volcanic eruption caused72ka BP climate events, but Y02stalagmite’s carbon isotope curve is not recorded72ka BP climate events in72ka BP. A part of deep-sea deposition and island near the Toba volcano is also not sudden changing. These different geological record did not response of the climate and environment changes before and after the Toba volcanic eruption. It may indicate that Toba volcanic eruption did not cause significant changes in the surface environment. So, it’s not concluded which Toba volcanic eruption caused the72ka BP climate events, It needs more low latitudes, high resolution geological records for verification.(3)Yangzi Cave Y02stalagmite’s five kinds of trace elements of Ca, Mg, Sr, Ba and U analysis results show that: In60～85ka BP period, Y02stalagmite’s Mg/Ca, Sr/Ca, Ba/Ca and U/Ca ratio is influenced by monsoon rainfall. When the summer wind to strengthen, precipitation increased. As a result of the PCP, the microelement ratio such as Mg/Ca is partial light. Y02stalagmites oxygen carbon isotope records and trace elements ratio have response of H6events. And Y02stalagmites oxygen carbon isotope records and trace element ratios are shown the start time of H6event in about63ka BP. As we can be seen from Y02stalagmites trace element ratio curve:stalagmite’s trace element ratios have three times undulation in70.5～72.5ka BP period. And the curve have most violent undulation in70.6ka BP, corresponding to the paleomagnetic Toba volcanic eruption of sea surface temperature (SST) record. The most violent undulation corresponding to the sea surface temperature (SST) record of the Toba volcanic eruption. Y02stalagmite’s trace element ratios have twice undulation before the Toba volcanic eruption. Therefore, Toba volcanic eruption did not lead to weather event in about72ka BP.(4)The power spectrum analysis results of Y02stalagmite’s oxygen carbon isotope records show that the hundred years scale of solar radiation is the main drive mechanism of climatic factors during60～90ka BP period. And wavelet analysis shows that the climate change also has around5000a time in the cycle.Y02stalagmite record of trace element ratio can draw the conclusion that different indicators of climate events recorded in the response is different in the stalagmites. Stalagmites so used to reconstruct paleo-climate, should use a variety of alternative indicators stalagmites, comprehensive study of the ancient climate change.