Surface microtextures of quartz grains from glaciolacustrine sediment core from Priyadarshini Lake, Schirmacher Oasis, East Antarctica as revealed under scanning electron microscope

摘要

The surface microtextures of quartz grains have been used as an important tool for interpreting transportation and depositional history of detrital sediments. Quartz grains from five segments of a 32-cm-long, undisturbed sediment core retrieved from Priyadarshini Lake have been studied under scanning electron microscope.Debris supplied by ice mass through melt-water streams embouching in the lake and windborne sediments are present in the cores obtained irrespective of their various segments. The sediment column consists of relatively fine-grained material because the water is almost stagnant or has a low flow velocity, enabling even the finest particles to get settled. Various microtextures and microtopographical information observed on the quartz grain surfaces indicate predominance of intense mechanical textures characteristic of glacial transport. Most often several stages of crushing and weathering are noted. Grains are mostly angular to subangular having high relief, large conchoidal fractures, deep troughs, arcuate fracture patterns, subparallel and parallel steps, striations, breakage blocks, adhering particles, oriented scratches and grooves belonging to glacial origin. Dish-shaped concavities, small conchoidal fractures, collision pits, edge rounding are attributed to aeolian transport of grains. Features related to chemical origin are represented by mild dissolution etching and silica precipitation in the form of amorphous and cryptocrystalline overgrowth suggesting precipitation on immobile grains under lacustrine environment.The assemblage of microtextures exhibiting multiple events of glacial crushing overprinted on single grains and different degrees of dissolution features that are discernible are grouped and discussed in the present paper.