A Study On Ecology And Environment Process Of Cenozoic Qinghai-Tibet Plateau Hinterland

The Qinghai-Tibetan Plateau is a unique tectonic unit whose uplift not only resulted in its own evolvement of environment and ecology, but also influenced and changed the climate and environment of neighboring area and the globe at the same time by giving an impact on the atmospheric circumfluence. The plateau uplift is a staged historic process that is recorded by the sediments through which we can clearly understand the information of plateau development and environmental transition. Because huge high mountains have magnifying action on climate changes, the Qinghai-Tibetan Plateau has also become the main study area of the Quaternary climate, environment and geology. As the background of regionally ecological evolvement, the uplift event of Qinghai-Tibetan Plateau and evolution of environment and ecology caused by uplift are analyzed in this paper, the time of plateau uplift and magnitude are concisely discussed. By using the flora ecological method, isotopic geochemistry, environmental geochemistry, environmental magnetics and sedimentology et al., the process of plateau climatic changes and ecological evolvement are discussed as emphases in the paper; aiming at the global warming and vegetation adapting of the way, extent and evolution-trend in modern times, the accordingly changed environment and ecology are detailed studied and the main conclusions are as follows:(1) Based on the information of sporopollen in Tongtianhe basin stratum profile and contrast study of to neighboring area, there have been 5 times of tectonic uplift in the Qinghai-Tibetan Plateau since the Eocene, which brought about the staged raising of plateau to elevation of present. The analysis of spore and pollen assemblage reflected that vegetation of studied area had undergone a converse process of succession from variable zone-broadleaves t o upland conifers to Savannaand to Alpine Steppe, the Yaxicuo formation stratum of E-Oligocene mainly had upland conifers grown, and presumedly had plateau elevation of 1000— 15000m. Because the primitive plateau monsoon possibly caused by the Miocene tectonic movement had brought about warm and humid climate, the vegetation components of Wudaoliang Formation of Neogene had large rise of semitropical component and presumedly had plateau elevation about 2000m. In the late Pliocene, Tibetan plateau had a herbage blooms such as Chrysanthemun Chenopodium, species were mainly spruce and fir, representing the vegetation characteristics of Savanna, and presumedly had elevation above 3000m. In studied area, spore and pollen assemblage of middle-Pleistocene are mainly composed of herbages, reflecting the plateau elevation should be above 4000m with the approximately similar environment and ecology to that of the present.