Inferences of Subglacial Processes Under the West Antarctic Ice Sheet From Grain Surface Textures

• Main Author: Wheeler, Aspen, '16
• Format: Text
• Language: unknown
• Published: DigitalCommons@IMSA 2016
• Subjects: Earth Sciences; Antarctic; West Antarctic Ice Sheet; West Antarctica; Whillans; Whillans Ice Stream; Antarc*; Antarctica; Ice Sheet
• Online Access: https://digitalcommons.imsa.edu/sir_presentations/2016/oralsession3/3; https://digitalcommons.imsa.edu/cgi/viewcontent.cgi?article=1032&context=sir_presentations

Subglacial sediment transport under Whillans Ice Stream in West Antarctica is inferred using samples collected from Subglacial Lake Whillans (SLW) and two sites at a location called “UpB”. The surface features on quartz grains between 125 and 1000 micrometers were described using a Scanning Electron Microscope. Mahaney’s Atlas of Sand Grain Surface Textures and Applications (2002) was used to uniformly and unbiasedly categorize surface features from SLW and UpB, for different grain sizes and depths in cores collected from subglacial till. Data showed three groups that can be used to delineate phases of the subglacial sediment. Phase one is shown by features indicating surface weathering formed while grains were in their original rock outcrop. Phase two is features overprinted on phase one, which indicate glacial transport within subglacial till due to the high frequency of glacial transport features. The final phase is younger weathering features that overprint the glacial transport features such as etching and precipitation features attributed to microbiologically-mediated chemical changes. This supports the view that subglacial transport occurs in till rather than in the waters that fill and drain SLW. Furthermore, microbial activity detected in SLW sediment and waters is likely to be pervasive up-stream from the lake.