Characterization of grainsize and grain shape of several sediments from the mountainous areas of southwestern Sichuan
Objectives:Due to the multi-mineral,and polymorphic feature of natural sediments,there are significant differences in the results obtained by different grainsize analysis techniques and data processing tools,but these differences have not been effectively and rationally assessed for a long time.In this paper,we aim at assessing the influence of different testing techniques and data processing methods on the final results.It also explores the similarities and differences in the grainsize and grain shape characteristics of sediments from different sedimentary environments in conjunction with grain shape information.Methods:Twenty-five samples from different sedimentary environments were subjected to the same pretreatment,and the grainsize analysis was completed on a dynamic image analyzer and a laser diffraction analyzer;the test results were statistically analyzed by the moment method and the graphic method,and the parameters of the sample size distribution were calculated.Based on the calculation results,scatter plots were established between the image method and the laser method and between the moment method and the graphic method to evaluate the effects of different testing techniques and different processing methods on the final results.Meanwhile,the two-dimensional density distribution plots of DE(diameter of equivalent projected area circle)—Sp(sphericity)were used to analyze the clustering of the grains of different samples and to investigate the relationship between the characteristics of grainsize—shape and the deposition environment.Results:① The mean grainsize calculated by the graphic and moment methods are almost identical,especially for the fine-grained portion of the samples,which is almost indistinguishable;the sorting coefficients of the two calculations are strongly correlated,but the moment method is usually larger.② Only for the skewness and kurtosis of normally distributed samples,the results of the graphic method and the moment method are similar.Only the mean grainsize of the laser method is moderately correlated with that of the image method;with the image method as a reference,the other higher-order grainsize parameters are almost irrelevant to the actual situation of the samples.③ There were significant differences in grainsize distribution,peak state,peak position and peak value obtained by the two measurement methods.It was found that the laser method grainsize was coarser than the image method in some samples in mountainous environments,which was presumed to be mainly related to the multi-mineral properties and multi-shape irregularities of the samples.④ The 2D density distribution plots of DE—Sp can be used to distinguish different grain clusters within the sediments,which may also have different planar spreading patterns.Conclusions:Compared with the laser diffraction method test technology and the graphic method estimation method,the estimation of grainsize statistical parameters from the dynamic image method results using the moment method can more objectively reflect the grainsize distribution characteristics of natural sediments.Combined with the 2 D density distribution of diameter of equivalent-projected-area circle(DE)—sphericity(Sp),the dynamic image method Dynamic image method can provide new potentials and opportunities for the analysis of sedimentary environments.
万方数据
维普
