Factor analysis of sphericity and roundness data of clastic quartz grains: Environmental significance

The first four sample statistics of two-dimensional projection sphericity and those of two-dimensional projection roundness of clastic quartz grains belonging to river, beach and eolian environments and to the three size grades 0.350 mm-0.297 mm, 0.297 mm-0.250 mm and 0.250 mm-0.210 mm were subjected to R-mode factor analysis. The results show that the particles of these size grades are carried largely as a traction carpet in the river and beach environments and are carried largely by saltation in the eolian environment. Sorting and abrasion are the causes of areal variation in the mean sphericity and mean roundness of a population, respectively. Selective sorting causes nonnormality in the sphericity distribution, whereas roundness distribution is originally nonnormal. Selective sorting is most effective in the eolian, less so in the beach and least so in the river environment, and consequently sphericity-nonnormality constitutes a valuable parameter for environmental discrimination. Intensity of rounding is highest in the beach, less in the eolian and least in the river environments. Due to its wide variation from environment to environment the mean roundness constitutes a valuable parameter for differentiating different environments. Sphericity variables contribute more to the discrimination of environments than roundness variables.