Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

• Published in: Antarctic Science
• Main Authors: Winsor, Kelsey, Swanger, Kate M., Babcock, Esther L., Dickson, James L., Valletta, Rachel D., Schmidt, Daniel F.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Cambridge University Press 2020
• Subjects: ground-penetrating radar; major ion geochemistry; McMurdo Dry Valleys; permafrost; water tracks; X-ray diffraction; Antarctic; Dammed Lake; Wright Valley; South Fork; Labyrinth; Don Juan Pond; Antarc*; Antarctic Science; Antarctica; Ice
• Online Access: https://doi.org/10.1017/s0954102020000139

The South Fork of Wright Valley contains one of the largest rock glaciers in the McMurdo Dry Valleys, Antarctica, stretching 7 km from the eastern boundary of the Labyrinth and terminating at Don Juan Pond (DJP). Here, we use results from ground-penetrating radar (GPR), qualitative field observations, soil leaching analyses and X-ray diffraction analyses to investigate rock glacier development. The absence of significant clean ice in GPR data, paired with observations of talus and interstitial ice influx from the valley walls, support rock glacier formation via talus accumulation. A quartz-dominated subsurface composition and discontinuous, well-developed desert pavements suggest initial rock glacier formation occurred before the late Quaternary. Major ion data from soil leaching analyses show higher salt concentrations in the rock glacier and talus samples that are close to hypersaline DJP. These observations suggest that DJP acts as a local salt source to the rock glacier, as well as the surrounding talus slopes that host water track systems that deliver solutes back into the lake, suggesting a local feedback system. Finally, the lack of lacustrine sedimentation on the rock glacier is inconsistent with the advance of a glacially dammed lake into South Fork during the Last Glacial Maximum. © 2020 Antarctic Science Ltd. Received 1 August 2019, accepted 11 December 2019. Published online by Cambridge University Press: 11 March 2020. The authors would like to thank Earl Ada for assistance and use of the Plastics Engineering XRD facility. Fred Luiszer (University Colorado Boulder) performed major ion analyses. Special thanks are given to the science support staff at McMurdo Research Station, including the personnel of Crary Laboratory, Helicopter Operations and the Berg Field Center. Finally, thanks are given to Warren Dickinson and one anonymous reviewer for their comments and suggestions, which greatly improved the manuscript. Author contributions: KW, KMS, ELB and JLD contributed substantially to the writing ...