THE MICROMORPHOLOGY OF GLACIAL AND NON-GLACIAL CLASTS: EVALUATING THE EFFECTS OF LITHOLOGY AND AGE

There is limited data regarding the analysis of micro-features and characteristics of striated clasts thought to have a glacial origin (Wentworth, 1926; Judson and Barks, 1961; Bjørlykke, 1974, Hicock and Dreimanis, 1989). However, preliminary research on striated clasts and surfaces from a variety of depositional environments suggests scanning electron microscopy (SEM) of striated clasts with varying lithology from diamictons may prove useful in defining a glacial origin. Evaluating whether SEM analysis of clasts from questionable glacial deposits is an applicable technique to define a glacial origin required a better understanding of the micro-characteristics of glacial and non-glacial clasts. We describe the micromorphology of surface textures and characteristics for samples of quartzite, granite, limestone, basalt, chert, pillow basalt, and quartz pebbles collected from environments of varying age.

Samples from known glacial environments are dominated by arc shaped steps, chattermarks, curved grooves, deep troughs, fracture faces, linear steps, relict polish, subparallel linear fractures and subparallel crushing features. Breakage blocks, scouring features, and v-shaped percussion features characterize samples from known non-glacial environments. Similar to previous studies investigating the micromorphology of quartz grains (Brown, 1973; Krinsley and Doornkamp, 1973; Folk, 1975; Mahaney et al., 1988; Mazzulo and Ritter, 1991; Mahaney et al., 1991; Campbell and Thompson, 1991; Mahaney and Kalm, 1995; Mahaney, 1995; Mahaney et al., 1996; and Mahaney and Kalm, 2000) we find that distinct microfeatures occur on striated clasts and surfaces with a glacial origin and suggest they can be used to differentiate between diamictons of a glacial versus non-glacial origin.