ABSTRACT

Gravel particles of different lithology, and similar particles transported over different distances show variations in shape and surface texture which may be detected and analyzed quantitatively by the modified Fourier procedure. This sensitive method of analysis of planar sections of particles is combined in this study with observations of the surface morphology of selected pebbles on the scanning electron microscope. Proglacial gravels composed of quartzite pebbles from the Onoway Channel northwest of Edmonton and gravels composed of quartzite and limestone pebbles from the Calgary area were investigated; both suites of pebbles were derived from the Cordillera. In the Fourier method the combined effects of shape and surface texture are defined as total roughness. Numerical values of roughness, shape and texture coefficients and mean harmonic amplitude spectra plotted graphically show the differences in contribution of shape and surface texture to total roughness of gravels. The Calgary quartzite pebbles have the least elongated but at the same time the most textured average profile, limestone pebbles of the same erosional history transported over the same distance are the most elongated; Edmonton quartzites are the least textured particles studied. Preliminary results on size-roughness relationship indicate that in general all gravels show a decrease in total roughness with decrease in particle size. However, there are marked differences in shape and texture for particular size groups.