Quaternary Glacial Geomorphology And Glacial Deposits Features Of The Taibai Mountain,Qinling Mountains

Qinling Mountain is located in thetransition zone between the eastern hilly area and western mountain area on the Chinese plain,it is the dividing line between the China subtropical monsoon climate zone and temperate monsoon climate zone,and it is a watershed of the Yangtze River and the Yellow River.The highest peak,Taibai Mountain(3767 m asl.),is recognized as a mountainous region where Quaternary glaciers developed in eastern china.Many researchers have been made document the glaciations of Tabai Mountain,as well as the mountain evolution,and geology vertical belts.In this paper,the author studied the glacial landforms and deposits of the Taibai Mountain,by field investigations and applied laboratory experiments from 2014 to 2017.The author studied the Quaternary glacial landforms of Taibai Mountain,and applied flat index to the cirques between the Dawengong Temple and Baxiantai Peak.The flat indexes are between 1.59 and 2.90,with its average of 2.01.Two sets of cirques are observed,with elevations between 2600m-2700 m and 3200m-3650 m,respectively,indicating two glaciations existed in the Taibai Mountain area.The equilibrium line of the two glaciations in the Quaternary are speculated to be located on 2600m-2700 m and 3200m-3650 m,respectively.Scanning Electron Microscopy was applied to the glacial quartz,to obtain their micro-textures.The glacial quartz are characterized by angular to sub-angular outline;mechanical features are conchoidal fractures,striations,adhering particles and cracks;chemical features include precipitation,dissolution and crystal growth are also observed on the glacial quartz.The author also applied Electron Spin Resonance(ESR)dating and Optically Stimulated Luminescence(OSL)dating to the glacial deposits of the Taibai Mountain.ESR dating result of the Baixiantai(3282 m asl.)is 24 ka,corresponding to the Last Glacial Maximum(LGM,24-18 ka)and Marine Isotope Stages 2(MIS2).OSL dating results are relatively younger than expectation,thus the author analyzed applicability of OSL dating in the glacial geochronology.The author studied the Quaternary glacial remains from macro-scope and micro-scope,using qualitative and quantitative methods,trying to obtain the timing and spacing information of Quaternary glaciers in the Taibai Mountain.This case study also provides a reference with which to discriminate between glacial sediments and non-glacial sediments,especially in controversial areas such aseastern China.