Sichuan Luoji Mountain At The Last Glacial Period And Environmental Evolution

Luoji Mountain (4359m) is located in the eastern edge of Tibet Plateau, the southwest ofSichuan, west of Peace River Valley, east of Qionghai Lake-Jing Liangzi-Pugh Rift Valley,is the one of China’s ancient glaciation in Eastern and clear without modern glaciation area. Ithas important science significance to study on the edge of the Tibetan Plateau and mountainglaciers coupling relationship between the development with the climatic and tectonic. TheQuaternary glacial relics distribution at an altitude of2500m above, the glacier landformtypes of complete, preservation of the intact in China known mountain is rare. Through fieldinvestigation and sampling analysis of landforms, sediments in laboratory indexes, electronspin resonance (ESR) dating, grain size characteristics of Luoji Mountain, glacier sedimentgeochemical analysis were determined and analyzed and the snowline calculation, moderateprecipitation conditions of gas recovery during the last glacial stages of glaciation during thelast glacial sequence, divided Luoji Mountain area and discuss the Mount Luoji MountainEnvironment evolution.Using relative geomorphological method field landform in the inspection process, and theinterior of electron spin resonance (ESR) absolute dating, glacial ice into the sequence ofLuoji Mountain Division: Early in the last glaciation(MIS4,84±11ka), The middle of the lastglaciation (MIS3b,58±7ka), the last glacial maximum (MIS2,14±2ka,17±2ka,13±2ka,26±4ka,33±4ka).Through the analysis of characteristics of particle size of the sediment, the bedrock tofeldspar sandstone, different period till showed smaller differences in sediment particle sizecomposition; average particle size, between-0.55~2.233mm, the average value is1.3709mm, Qingshui channel during the last glaciation early value is2mm, the middle of the lastglacial period value is0.91mm, the last glacial maximum value is0.822mm, due to theinfluenced of tectonic movement, the three stages of deposition during the last glacial period,the grain size gradually thin, Show that glacier size is smaller than one at a timeThrough electron microscope observation of quartz sand particles, quartz particles inglacial sediments has the characteristics of the oceanic glacier development: the Particle shapeis irregular, particle surface fluctuation, the angular, slightly rounded, shell port, smoothcleavage planes, parallel and arc cleavage step, and SiO2precipitation. Look the findingsfrom the particle grinding degree, early last-glacial quartz particles relatively rounded,suggesting that depositional ages ago. Comprehensive observe the erosion accumulation,sediment multi-index analysis and ESR age determination, Comparative with the development scale of the three stages of the last glacial Luoji Mountain, MIS4than MIS3b more than MIS2stage, trends in this area during climate for the last glacial period: early (MIS-4) climate of the time is Cold and dry climate, lowrainfall, sediment dominated by physical weathering. During the last glacial period (MIS-3b)when the climate is A cold and dry, but relatively early warmer, Precipitation the least, Weathering is given priority to with physical weathering. The last glaciation maximum (MIS2) climate: Climate from the cold wet to cold dry excessive, Physical weathering is more and morestrong.