MICROTEXTURES ON QUARTZ GRAINS IN TILLS FROM ANTARCTICA

Quartz grains of the sand (63-2000 mu m) fractions from tills of Oligo cene to Quaternary age in Antarctica were analyzed by scanning electro n microscope (SEM) to test the hypothesis that relative ice thickness and distance of transport influence the type and range of microtexture s observed on individual grains. In this study, replicated subsamples were analyzed from tills emplaced by thick glaciers with both short an d long transport distances. Till samples with grains transported over long distances (up to several hundred km) under thick ice (<1000 m) we re compared with quartz grains from relatively thinner (e.g. 500 m thi ck) outlet glaciers with shorter transport distances (<100 km). A rang e of microtextures including subparallel linear fractures, conchoidal fractures, are-shaped steps, grain relief, edge sharpness, grain angul arity and roundness, straight and curved grooves, crescentic gouges, d issolution features, precipitation features and presence of adhering p articles was used to determine the environmental history of these grai ns. Microtextures on sand-size clasts including microfractures, abrasi on, etching and coatings can provide important information on paleoenv ironmental history including glacier activity and severity of weatheri ng inferred from etching and dissolution features.