Quaternary Glacier Development And The Coupling Effect Between The Climate Change And Tectonic Uplift In The Mayaxue Shan

Mayaxue Shan (main peak is4447m), which is located at the northeast of Tibetan plateau,is a key site to discuss the coupling effect of climate and tectonic playing an important role in glacier development.Glacier sequence of Mayaxue Shan is the core. With field investigation in north and south of Mayaxue Shan, We found tipical glacial erosion and deposit landform.applying optically stimulated luminescence (OSL) method to sediments, such as glacier moraine、 debris flow and other tills, ages are as follows:glacier moraine (42.6±1.9ka,45.7±3.0ka) and the up tills, which belongs to the middle of last glacial cycle,corresponding to MIS3b; glacier moraine (23.2±1.0ka) and debris flow (42.6±1.9ka,45.7±3.0ka),which indicate the LGM glacier advance Combine relative landform with OSL chronology, the glacial sequences can be assigned as the MIS3b and LGM, and the former has a larger extent than the latter,because the former extent to3000m, but the latter only to3300m. Base on the formula we calculate the modern equilibrium line altitude (ELA) and last glacial cycle ELA as4900m and4100m respectively.Sediment analysis indicates several environmental indexes:Analysis of magnetization in Mayaxue Shan shows that the magnetic susceptibility value is very low.It is not only mainly related to lithologic of Mayaxue Shan, but also can indirectly reflect the Mayaxue Shan undergone a weak weathering and limited humid. Element geochemical analysis results show that MIS3b climate was humid, which coincide with the record of Guliya Ice Core. Particle size analysis shows that compare with LGM period the silt sand content is higher than clay during the MIS3b,mainly attributing to the humid climate during MIS3b and the strong chemical weathering. On the contrary, the temperature is low and precipitation is small, resulting in strong physical weathering and high content coarse size.Another reason may be that the glacial scale during MIS3b is larger than LGM, and the glacial transfer ability is so strong to deliver the moraine till to far distance.Base on terrace undercutting equal to mountain uplift, Mayaxue Shan has upraise100-140m since the last glacial cycle, and according to10Be date calculating the erosion rate of25mm/ka, corresponding to erosion amount of2-4m. We recovery the watershed hight of 4150-4100, reaching the ELA (4100m) of last glacial cycle, and then develop glacier. So thecoupling effect of climate and tectonic attribute to the glacial development.