Climate Change Record Of Qiongduojiang Basin In Southern Qinghai-Tibet Plateau Since The Last Glacial Stage

In recent years, Paleoclimatology has become a heated topic in contemporary geological science due to its unique research reference value on modern climate change. In many deposition carriers saving climate information, lacustrine sediments has its unique side on researching climate and environment change, considering its characteristics of wide distribution, relatively few limited conditions, continuous stable deposition, high resolution and easily extraction. By studying the climate proxies of the plateau lacustrine sediments, it has important research value to study the climate change of Qinghai-Tibet Plateau, especially the influence of the formation of the Plateau to the Asian monsoon system, and to illustrate the control factors and dynamic mechanism resulting in the climate change. Therefore, in this paper, by extracting the granularity, TOC content, the TOC / TN ratio and ?13Corg substitute indexes of Qiongduojiang Basin lacustrine sediments and based on the framework of AMS14 C chronology, the paleoclimate evolution of the research area is analyzed. By comparing with the other global regions such as the monsoon area in stalagmite oxygen isotope record, North Atlantic Sea surface temperature and solar radiation, it is preliminarily discussed on the dynamic mechanism driving the climate change and the conclusions are as follows:1. Using AMS14 C Dating, the age of the Qiongduojiang Basin lacustrine sediment section is limited in 40.2 ka ~30.3 ka BP.2. Through the analysis of every proxies, the characteristics of 40~30 ka BP Paleoclimate change in Qiongduojiang Basin are divided into the following several stages: the warm humid climate period(40.2~38.5 ka BP)?the warm arid climate period(38.5~35.4 ka BP)?the transition climate period(35.4~32.4 ka BP)?the volatility climate period(32.4~31.7 ka BP) and shift to arid climate period(31.7~30.3 ka BP). By analyzing the proxies, it is discovered that there are several obvious climate change events during 40~30 ka in the Qiongduojiang Basin, such as transient arid event at 39.3 ka, precipitation enhancement event at 35 ka.3. Through analyzing the organic carbon isotopic variation characteristics of the lacustrine sediment profile in the Qiongduojiang Basin, it is illustrated that the atmospheric CO2 concentration aparting from the factors influencing the temperature and precipitation is also probably one of the reasons leading to the organic carbon isotopic change in the profile.4. Combining with the organic carbon isotopic variation characteristics of the Qiongduojiang lacustrine sediments, the results has evident response to that of the other global area. In the frequency spectrum analysis, 1552 a?1187 a?961 a?602 a are identified, a series of cycles of which are well corresponding to the 1.5 ka and 1 ka period in the D / O cycle, and 602 a, 538 a, 492 a possibly corresponding to the half 1000 a cycle.5. When comparing with the Nanjing Hulu Cave stalagmite oxygen isotope variation curve controlled by East Asian monsoon, it is discovered that the two areas have incongruous climate change relationship, which is preliminarily interpreted into different monsoon risk controls resulting in the differentiation in the two areas. Comparing the climate record in every area, that the basin climate control is mainly affected by the southwest monsoon, weakly related to the East Asian monsoon, is known. It could be good comparative study on the Guilin Xiangshui Cave stalagmite oxygen isotope analysis. In addition, by contrasting with the climate events reflected by the climate records of North Atlantic deep-sea sediments, it also has good comparative quality, indicating that it is possibly driven by thermohaline circulation. However, considering the special geographical position and the tectonic landscape. structural factors of the plateau, the thermohaline circulation and the plateau itself is two main important factors influencing the lacustrine sediment climate parameters of Qiongduojiang Basin.6. Taken the solar radiation change at 30°N and 30°S since 40~30 ka BP into consideration, an initial conclusion is obtained that the climate and environment change is generated by the variation of the solar radiation, and the solar radiation differences of the north and south latitude at about 32 ka BP is likely to be one of the causes leading to the dramatic climate turbulence of the Qiongduojiang Basin.