Research On The Quartz Sand Surface Texture Of Sandy Sediment From Changxing Island In Dalian

The sedimentary profile of the Shelf sand exposed to the surface and retained in the area of Changxing Island in Dalian is selected as the object of the study.Qualitative analysis and quantitative analysis were used to analyze the grinding roundness,mechanical surface texture,chemical surface texture and mechanical-chemical surface texture of quartz sand from the sand layer,the transition layer and the loess layer by means of the scanning electron microscope?SEM?,and the formation environment is also analyzed.In addition,a number of samples of modern beach sand were collected and compared with the quartz sand surface texture of Shelf sand.?1?All the samples of the Shelf sand profile of Changxing Island developed different degrees and different types of combinations mechanical surface texture,chemical surface texture and mechanical-chemical surface texture.Coarse quartz sand and the middle-fine quartz sand of the sand layer,the transition layer and the loess layer from the Changxingdao profile are mainly in sub-angular and sub-circular shape,the circular shape is occasionally seen in the coarse sand,and the angular shape is occasionally seen in the middle-fine sand;the mechanical surface texture of quartz sand are all generally developed with wind-forming environment features such as dish-shaped pits,mooned pits,pitting,meandering ridges and flip flakes and texture of underwater environment such as mechanical V-shaped,underwater polishing surface,straight and curved grooves and so on.In addition,and there are two common environmental characteristics associated superimposed.The occurrence frequency of underwater environment in the sand layer is higher than that in the loess layer,while the occurrence frequency of wind-forming environmental characteristics of meandering ridges,pitting is lower than that of the loess layer.It is inferred that the sand transport distance is closer and the loess transport distance is farther.The chemical surface texture developed a large number of corrosion pits,deep corrosion trenches,scaly spalling and SiO₂ precipitates high-energy chemical environment,as well as corrosion shallow trenches,SiO₂ precipitation film,corrosion pits low-energy chemical corrosion environment.The SiO₂ Precipitation on the surface of quartz particles in the transition layer is remarkable,with remarkable transition characteristics.The sand layer precipitation is more developed and loess layer corrosion is more developed.The mechanical-chemical surface texture of quartz sand are mainly middle and high protrusions,and the occurrence frequency of cohesive particles is higher.?2?The surface of quartz sand in modern beach sands develop different degrees grinding roundness,mechanical surface texture,chemical surface texture and mechanical-chemical surface texture.The grinding roundness is characterized by sub-angular and sub-circular shape,a few of which are angular,and no round particles are found.On the surface of quartz particles,there are mechanical surface texture such as V-shaped,underwater polishing surface,meandering ridges,scale conchoidal fractures,pitting,flat cleavage plane,parallel step-like fractures,straight and curved grooves,dish-shaped pits,mooned pits,the underwater environmental characteristics of V-shaped,underwater polishing surface and straight/curved grooves are more significant than Shelf sand profile.Meandering ridges and pitting are widely developed,while dish-shaped pits and mooned pits are occured normally,compared with Shelf sand profiles,the frequency of occurrence is lower,and the superimposed characteristics of the two environments are obvious.The chemical surface texture developed scaly spalling,corrosion pits,deep corrosion trenches,directional corrosion pits,siliceous scales,thin films and crystal growth.Among them,the frequency of crystal growth is 100%,the effect of underwater environment is obvious,the scaly spalling phenomenon is few,and the siliceous bulb is not observed.The degree of chemical modification of beach sand is lower than Shelf sand,and the surface of particles is cleaner.The mechanical-chemical surface texture of quartz sand are mainly middle and high protrusions,and the frequency of cohesive particles is 100 percent.A comparative study of surface morphology of sandy sediment profile and modern beach sand shows that sandy sediments have the typical features of aeolian sedimentary,while modern beach sands have obvious hydrological sedimentary characteristics,and there are obvious differences between the two sedimentary characteristics.?3?The Shelf sand profile of Changxing Island was formed at the end of Late Pleistocene,which was formed by the interbedding of sand and loess.The characteristics of wind-forming environment and underwater environment are developed,the accompanying and overlapping characteristics of the two environments are significant,and most of the wind-forming environmental characteristics of the particle surface are overlapped on the underwater environment characteristics.The occurrence frequency of the underwater environment is higher and the chemical precipitation is significant.The characteristics of the wind-forming environment in the loess layer are obvious,and the characteristics of the underwater environment are also developed.The Liaodong Peninsula is a monsoon climate area with strong winter monsoon,the dust from the inland and the nearby seabed plain is carried by the wind and flowing water to accumulate here and the loess deposits are formed.Because of the alternation of the glacial periods and the interglacial periods,a transitional feature is formed between sand layer and loess layer,and the interbed deposition of sand and loess is formed.