Quaternary Glacier Remains And Glaciation Evolution In The Southern Section Of Heilongjiang Province Zhangguangcailing Mountains In The Fenghuang Mountains Area

Fenghuang mounatins is located in the southeastern part of Heilongjiang Province,south of Zhangguangcailing Mountains and to the east is Songnen Plain.In order to provide new evidence for the Quaternary glacial problems in eastern China and improve the evolution law of Paleoclimate and Paleoenvironment in northeastern China,the Quaternary glacial geomorphology,Scanning Electron Microscopy(SEM)characteristics of moraine quaetz sand and Paleoenvironmenttal characteristics(Sporopollen analysis)and glacial evolution history in Fenghuang mountains area were studied in this paper.The Quaternary glacial landforms in Fenghuang Mountains area mainly include cirque,firn-basin,glacial valley knife-edge crest,horn and moraine platform.The cirques mouth face in all direction and as the center of Fenghuang Mountains.The elevation of cirques is from 800 m to 1550 m.The flat index of typical cirque in Fenghuang Mountains is between 1.72 and 4.56,with the average value is 2.18.The firn-basin developed on the top of Fenghuang Mountain(Hanging Garden)and now is an alpine marsh wetland.The overall observation of moraine is gravel layer with diameter of more than 5~200cm.The gravel lithology is mainly granite,andesite and vein quartz,etc.The gravel is poorly sorted and arranged in an undirected manner,mainly in the form of sub-edge angle-sub-circle.The Scanning Electron Microscopic(SEM)characteristics of moraines quartz sands are as follows: sharp edges,sub-ridges,medium-high fluctuations and poorly rounded quartz particles.Typical mechanical characteristics are mechanical V-shaped pits,scratches,adherent debtis,shell-like fractures and steps.Frequency analysis shows that the development of glacial environment and water flow environment is similar,and the frequency of glacial genesis is slightly higher than that of water flow,but they are much larger than the aeolian formation.A comprehensive annlysis of the characteristics and frequency of the moraine quartz sand in Fenghuang Mountain is carried out.The formation environment shoud be mainly due to the interaction of glaciers and flowing water,or in the meltwater,the tupe of glaciers belongs to marinr mountain glaciers.The result of sporopollen analysis in moraines showed that pollens of woody plants such as Pinus,Picea,Tilia,Hippophae,Juglans,Quercus were found;pollens of herbaceous plants such as Gramineae,Chenopodiaceae,Compositae,Artemisia,Xanthium,Cruciferae and fern spores such as S.sinensis and Lycopodium were obtained from all sanples.The average sporopollen concentration was 52 grains/g,in the sporopollen assemblage,the pollen of herbaceous plants(72.66%)was dominated by Chenopodiaceae(37.54%)and Artemisia(32.17%)followed by Compositae and Gramineae,etc.The pollen of woody plants(24.79%)was dominated by Pinus(20.59%)as well as Picea,Alnus,Quercus,Ephdra and Hippophae.Ferm spores(2.55%)could be found in S.sinensis and Lycopodium.At that time,the vegetation in Fenghuang Mountains area was mainly sparse forest grassland with Artemisia and Chenopodiaceae,and the climate was cold and dry.Considering the sedimentary age of moraines and the glacial geomorphology,the Fenghuang Mountains area can be divide into two glacial periods,the early last glacial peiod and the middle-last-glacial-Last Glacial Maximum.The OSL ages of the samples were mostly concentrated in the range of 18 to 24 ka.The ESR ages varied greatly,but the age of moraines became younger with the increase of altitude.Compared with the two dating results,the ESR age is significantly older than the OSL age,which indicates that the signal residual residual value of ESR dating in moraines does exist.