The Different Responses Of The Asbestos Oxygen And Carbon Isotope Records To The Last Ice-eliminating Process

The main characterization of global climate change is glacial-interglacial cycles during the late Quaternar.The process of the glacial-interglacial varies from one geological record to another.Especially,during the last glacial and deglacial period process,different patterns were showed by differentpaleoclimate proxies.High resolution stalagmite records have unique advantage and characteristic in response to the last deglaciation process except typical Arctic and Antarctic ice core record.In this thesis,a stalagmite was collected from Xiniu Cave,which is influenced by East Asian Monsoon.A climate evolution series of the last deglaciation is reconstructed based on 12 high-precision U/Th age controls as well as 642 oxygen and carbon isotope datas.The sample BF30 ?¹⁸O values in Xiniu Cave range from-11.46‰ to-5.91‰,with an amplitude of 6‰ over the whole record,which can sensitively respond to climate change.Good reproducibility and small standard deviation ensure the accuracy of the experimental data.Stalagmite BF30 ?¹⁸O variations show a strong resemblance to the Greenland ice core records,in which witnessed Heinrich?H1?and Younger Dryas?YD?.However millennial-scale events showdifferent internal structures between BF30 stalagmite ?¹⁸O variations and the Greenland ice core records.Whereafter,we compare BF30 ?¹⁸O reconstruction and Atlantic Meridional Overturning Circulation?AMOC?,finding similar millennial changes in BF30 ?¹⁸O and AMOC.Particularly,both of them contain two "Valley" events,implying that stalagmite ?¹⁸O of East China Monsoon region indeed reflect hydrological circulation and also indicating that the Asian monsoon?AM?has a corresponding relationship with marine climate.The continuous stalagmite carbon isotope reconstruction recovered from Xiniu Cave,which covers a period of 10-23ka BP,has a change in growth rate.In the early part of the record,there is a higher growth rate,along with larger amplitude of 2‰.On the contrary,during 17-10.75kaBP,contain lower growth rate and smaller amplitude of 1‰.We observe that the values in BF30 813C curve which were characterized by gradual and continuous negative trend.Our results show a direct link between a gradual change from the AM region and a variation in global isolation without millennial-scale shifts.There is a contrasting behavior of stalagmite oxygen isotope variations as compared with stalagmite ?¹³C record,whereas display a similar form of the Antarctic ice core.Both of sporopollen and continental temperature record aligned with the change in BF30 ?¹³C reconstruction.The carbon isotope record displays a different deglacial pattern to the oxygen isotope record from one stalagmite,perhaps representing an obvious imparity of them in reference.It is similar to the relationship between the continental temperature and carbon isotope record.As such,we could understand the potential role of such variability of stalagmite ?¹³C as a feedback on continental temperature.We gain the slope of stalagmite ?¹³CC and ?¹⁸O curves by linear regression equation.The result suggests that the whole slope of ?¹³C reconstruction is commonly associated with the three slopes of ?¹⁸O record,including value and direction.It is the evidence that the close correspondence between oxygen and carbon isotope curve trend,which can support them following insolation change on orbital time scales.The findings of millennial-scale climate variability observed in ?¹⁸O curve appear to support that oxygen and carbon isotope controlled by different climate factors.In addition,the rise in temperature according to our oxygen and carbon records is consistent on orbital time scales,which maybe interpret an early phase of global deglacial warming depending on the similar time??21.5ka BP?observed in oxygen and carbon curve.