Polar Eolian Sand Transport: Grain Characteristics Determined by an Automated Scanning Electron Microscope (QEMSCAN®)

Abstract

QEMSCAN®, an automated scanning electron microscope, is used to provide a high-resolution analysis of eolian sands collected from Victoria Valley, McMurdo Dry Valleys, Antarctica. This technique provides a rapid, digital, quantitative morphological and mineralogical analysis of sediments, originally developed for the mining industry, which we apply for the first time to the study of eolian sand transport. Results show fine to medium-sized sands (<300 µm) are similar in shape and mineralogy throughout the hyper-arid landscape of the Victoria Valley. We relate this to the almost continuous mixing of fine-grained sediments in the mostly snow- and ice-free valley by frequent thermally induced easterly winds and less common but stronger topographically channeled southwesterly foehn winds. Analysis of local dune sands transported during easterly winds, which typically just exceed the local threshold entrainment velocity of 5.3 m s−1 (at 0.4 m), indicate preferential transport of quartz grains by these winds. Surface type was found to exhibit considerable influence over the characteristics of eolian sand transport with much larger grains carried in saltation and modified suspension above fluvio-glacial outwash surfaces than above sand dunes. Results illustrate the potential of QEMSCAN as an effective tool for multi-parameter analysis of eolian sands allowing greater insight into the controls on eolian sand transport in settings such as the Victoria Valley, Antarctica.