Environmental Significance Of Sedimentary Matter Parameters Of Qinghai Lake In Tengchong, Yunnan And Climate Change Since The Last Ice

The change lead to the global sea level rose by an average of 120-140 m,which the global temperature overall recovery and a large number of ice melt from the mainland and the sea surface in the last deglaciation. The large amount of fresh water from the ice sheet disintegration will affect to some extent the SST change and the formation intensity of NADW(North Atlantic Deep Water). The abnormal changes of SST is directly related to the subtropical and tropical convergence zone formed, the intensity and position and moving path, and the impact is self-evident on the Indian monsoon and East Asian monsoon. The Yunnan-Guizhou Plateau with widely distributed lakes is located in the South Asian monsoon and East Asian monsoon convergence zone, which climate is mainly controlled by the South Asian monsoon and East Asian monsoon and also affected by the Westerlies and the regional climate of the Qinghai Tibet plateau. The lake sediments lakes is particularly sensitive to changes of the regional environment and it is irreplaceable in the reconstruction of various scale climatic and environmental evolution sequence, also is a good indicator of paleoclimatic and environmental evolution.In this paper, though the characteristics of grain size of the total organic carbon, carbonate, magnetic susceptibility and chronological analysis of Yunnan Tengchong Qinghai lake sediment core, we discussed the characteristics and the environment significance of the sediment index, and pointed out the particularity and change characteristics of the index in lake sediments. The study found that sediment grain size parameters, total organic carbon content, magnetic susceptibility and carbonate content is closely associated with the environment, which can accurately reflect the climate dry-wet change in the region. Apart from other areas of significant characteristic is that the carbonate content of lake sediment is closely related to lake water level, when the outflow of water is reduced to below the drain height, the carbonate content of lake sediment is almost zero, the carbonate precipitation formed. Therefore, very low carbonate content in the lake sediments indicate the high water level, the high carbonate with low water level indicator. Another notable feature is the high organic matte content of the lake sediment, reflecting the material input of organic matter, and the lack of runoff material, and are also associated with few atmospheric material input. In a typical southwest monsoon control area, the change of total organic carbon, despite the mutual influence of biomass, preservation conditions, mainly depends on the storage conditions and hydrodynamic conditions. When the rainfall is relatively small, the water overflow volume is less and even the spillover process will terminate, which is conducive to the enrichment of organic matter in the lake, but also conducive to the preservation of organic matter in the fine sediments. When the precipitation is more, though the basin biomass increased, but the more organic matter and fine sediments may be spilled water. Meanwhile organic matter content of qinghai lake is also affected by temperature. The higher temperature, the higher organic matter, on the contrary, the lower temperature the lower organic matter, which there is a good linear correlation. In a short time scales(one thousand, one hundred, 10 years), the sediment particle size increases reflect the short distance from the shore of lake, lake water levels fall indicate dry climate; conversely, the sediment grain size decrease reflect the sampling distance is away from the shore of lake, lake water level rise, indicating humid climate.On this basis, this paper reconstructed the environment and climate change of the Yunnan Tengchong since 15.70 ka BP. Though comparative analysis about ancient climate and environment change records with its adjacent area, we explore the differences of ancient climate and environment evolution between different regions in space. Through the reconstruction of the sediments sequence, comprehensive analysis of particle size distribution, total organic carbon(TOC) content, carbonate content and magnetic susceptibility, we found that the climate in Yunnan Tengchong shows the evolution process of cold-wet and warm- wet- dry and warm- temperate and dry, and it can be divided into 4 stages, stage I 15.70-12.77 Ka BP climate is cool and wet stage II; 12.77-4.68 Ka BP is the warm-wet period, more precipitation, high lake level; phase III 4.68-0.31 Ka BP shows the evolution from warm-wet to warm-dry climate, precipitation decreased, lakes water levels fall; stage since 0.31 ka BP,Ⅳ is moderate and moist climate characteristics as early. Late trend to warm-dry characteristics, in response to the trend of climate change because of global climate warming in recent decades.