Climatic fluctuation imprinted in quartz grains of lake sediments from Schirmacher Oasis and Larsemann Hills area, East Antarctica

摘要

Polymodal distribution of glaciofluvial sediments of Schirmacher Oasis and Larsemann Hills area of East Antarctica show traction and saltation as the most dominant mode of transportation. Quartz grains (of >65mu size) from these sediments are the best rock-forming minerals to study the mechanical action at microscopic level. Scanning Electron Microscopy (SEM) of these quartz grains show almost all glacial and glaciofluvial features on its surfaces, along with aeolian signatures modified by glaciofluvial action in some grains. Mechanical action by wind is more dominant on Schirmacher sediments than the Larsemann sediments. This study has also revealed climatic fluctuations in the vertical column. The sediments can be classified into three different types based on the SEM study. The first one is represented by glacio-fluvial sediments along with chemical precipitates. The second category is that of aeolian sediments, partly modified by glaciofluvial action and having chemical coating. The third type is mainly dominated by glacial sediments. Precipitation of silica and iron oxides indicates minor fluctuations in Eh-pH conditions of the depositing medium.