Abstract

Particle shape from gross form to surface texture is quantified using closed-form Fourier analysis of whole grain outlines from micrographs of 158 quartz sand grains representing subglacial transport and subaerial weathering in cold environments. Mean harmonic amplitude spectra and roughness coefficients are calculated. 1) Two-dimensional particle micrographs are a suitable surrogate for three-dimensional grain roundness and texture. 2) The particle size of sand grain sample affects it roundness and texture, and only samples of similar size range should be compared. 3) Fourier shape analysis distinguishes differences between basal and englacial grains, the latter being more angular and rough in texture. This is relevant to definition of debris transport paths through glaciers. The technique may also be useful in the interpretation of marine sediments from cold regions, and pre-Quaternary diamictites of controversial or unknown origin.--Modified journal abstract.

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