Abstract:

After weathering of the rock,its quartz grains may be transported,abraded and deposited.These processes give rise to various secondary surface features.The study of these surface textural features,especially the features of their combination,may allow us to reconstruct the sedimen- tary environment and evolutional history from one aspect.With the scanning electron microscope,the authors have studied thesurface textural features of the Quaternary quartz grains of morainic,glacio fluvial,eluvial,alluvial,diluvial,mud-rock flow,lacustrine and eolianorigin in Tibet,Sichuan,Xinjiang,North China,etc.This is of majorim portance for studying the quartz grains of other geological ages and recon-structing their sedimentary environments.Under different climatic conditions,the degrees of solution-precipita-tion of silica on the surface of the quartz grains are different.On thatbasis,three types of paleoclimate may be recognized:high-energy chemical,low-energy chemical and non-solution environmental types,which represent wet-hot,warm-cool and cold climates respectively.In this paper,according to the solution-precipitation features on thesurfaces of the quartz grains,the authors reconstruct the paleoclimate withreference to the example of the Quaternary geological section of the front of Mt.Longquan,Sichuan,and thereby negate the concept of“glacial deposits”proposed by predecessors.