A comparative SEM study on the micromorphology of glacial and nonglacial clasts with varying age and lithology

摘要

Preliminary research on striated clasts from a variety of depositional environments suggests that scanning electron microscopy (SEM) of striated clasts of varying lithology in diamictons may prove useful in interpreting a glacial origin. Evaluating whether SEM analysis of clasts from diamictons is an applicable technique to define a glacial origin requires a better understanding of the microfeatures occurring on glacial and nonglacial clasts. We describe microtextures and surface characteristics for samples of quartzite, granite, limestone, basalt, chert, pillow basalt, and quartz pebbles collected from a variety of depositional environments. Our study suggests that it is possible to differentiate between glacial and nonglacial deposits based on frequency and morphology of diagnostic surface microfeatures observed on entrained clasts. These microfeatures are best preserved and identified on competent and monomineralic samples (e.g., quartzite, chert, limestone) and poorly preserved on less resistant and polymineralic samples (e.g., basalt and granite).