Microtextures on quartz grains in tills from Antarctica

Quartz grains of the sand (63–2000 μm) fractions from tills of Oligocene to Quaternary age in Antarctica were analyzed by scanning electron microscope (SEM) to test the hypothesis that relative ice thickness and distance of transport influence the type and range of microtextures observed on individual grains. In this study, replicated subsamples were analyzed from tills emplaced by thick glaciers with both short and long transport distances. Till samples with grains transported over long distances (up to several hundred km) under thick ice (< 1000 m) were compared with quartz grains from relatively thinner (e.g. 500 m thick) outlet glaciers with shorter transport distances (< 100 km). A range of microtextures including subparallel linear fractures, conchoidal fractures, arc-shaped steps, grain relief, edge sharpness, grain angularity and roundness, straight and curved grooves, crescentic gouges, dissolution features, precipitation features and presence of adhering particles was used to determine the environmental history of these grains. Microtextures on sand-size clasts including microfractures, abrasion, etching and coatings can provide important information on paleoenvironmental history including glacier activity and severity of weathering inferred from etching and dissolution features.