The Quaternary Environmental Evolution Of Typical Lakes In Central Tibetan Plateau

This paper to the Tibet Peiku Co and Zhari NamCo Lake of the sedimentary strata as a main subject, and as the Quaternary geology,geomorphology,sedimentology,isotopic chronology,environmental geochemistry,ancient pollen and micro-biology,and other interdisciplinary theory and methods for guidance,carrying out a detailed study on the hinterland of Tibet Quaternary typical lake sediment profile, as well as restores the ancient climate and environment,analysizing its environmental evolution of lakes, comparing to the Nam Co environmental evolution and discussing the relationship between the lake evolution and uplift of the plateau.In this paper,research results and conclusions are as follows:1.The establishment of the Tibetan hinterland Quaternary early Pleistocene - Holocene lake formation units-Peiku dead wrong group(QP).Peiku dead wrong group is composed of four groups:the fourth group of the Pleistocene pull Yang Group(Qp^1ll),the Pleistocene Mang-freeze Group(Qp^2lm),updates on the EC-help group(Qp^3lb) and the new EC Rome-cloth Group(Qh^ll).These supply a new information for the evolution of the Qinghai-Tibet Plateau lakes,climate change research and the division and correlation of the Quaternary strata.2.Through the analysis of lake sediment particle size,susceptibility,carbonate,combining micro-paleontology,pollen portfolio,to restore the ancient environment and the ancient climate of the Peiku Co,Zhari Namco.The Peiku Co from the early Pleistocene - Holocene vegetation from coniferous forests - Woodland grassland - grasslands,from the humid climate to gradually develop in the direction of drought,reflecting the entire process,the formation of lakes→expansion→shrinkage.The vegetation in Zhari Namco is cold desert grassland in late Pleistocene,climate mainly to dry and cold,but in 88.8～87.8 kaBP,86.3～84.7kaBP,81～71kaBP,lakes emerged rose perid three times,lake water desalinated,lake water level rose and the climate was humid.3.Compared the change of the envirnorment of three typical hinterland of the Tibetan Peiku Co,Zhari Namco and Nam Co since the late Pleistocene.The conclusions are:(1) Peiry Co in the late Pleistocene was peak period,Experienced the shallow lake - semi-deep lake - deep lake process.Through analysis of the environment and stratigraphic sequence,determining the Peiku Co in the 56～31 kaBP period reached the deep lake environment.Zhari Namco in the 120～71 kaBP,the lake water level moved up and down, turning to the Great Lakes period.And Nam Co in the 115.9～78.5 kaBP reached the highest,followed by fluctuations in the overall decline.(2) the vegetation in Peiku Co and Nam Co are similar,mainly forest grassland,pollen to plants in the majority,and Zhari Namco herbaceous plants of the absolute superiority, for the alpine desert grassland vegetation.The climate and environment in Peiku Co and Nam Co are similar, which have mild climate,the climate of Zhari Namco is dry and the temperature is relatively low.(3) Peiku Co and Nam Co are about in 11 kaBP,the climate are the early partial to the dry side of the late wet change. That notes after 11 kaBP,the climate of Peiku Co and Nam Co are similar.4.Discussed the relationship between the climate evolution of the hinterland of the ancient highland and the uplift of the Qinghai-Tibet Plateau.Conclusion is that the uplift of the Qinghai-Tibet Plateau to the study area is an obvious impact on the climate and environment.The overall positive correlation - With the continuous increase in altitude,the general change trend of the climate and environment is cold and drought. But these two do not always linear,the evolution of climate and environment in hinterland of the Qinghai-Tibet Plateau Quaternary ancient should also be a combination of factors.