LEACHING AND SEM-EDS ANALYSES OF GLACIAL AND PROGLACIAL SEDIMENTS IN TAYLOR VALLEY, ANTARCTICA

The Taylor Valley (TV), Antarctica is largely ice-free with mountain glaciers serving as the source of melt water to supra and proglacial ecosystems. Cryoconite holes formed from eolian sedimentation on glacier surfaces are ice-lidded, water-filled depressions. Holes are isolated for seasons to years and drain into supraglacial streams. All TV waters host microbial life. This study examines the physical and chemical signature of sediments that have traveled from the surface of the Canada Glacier into the proglacial depositional environment termed ‘the beach’. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) analyses of these sediments reveal chemical and physical weathering, pyroxene alteration, dissolution features, sheeting along cleavages, and evidence of eolian transport. Leaching experiments were conducted on glacier surface sediments (dry), cryoconites, and proglacial stream,sediments from Andersen Creek. Glacial surface sediments (dry and cryoconite) are the eolian and meltwater starting point for the formation of beach sediment. To perform leaches, 5 grams of sediment were put in 50 ml of DI and filtered at 0, 0.5, 1, 2, 4, 8 and 24 hours. Major ions were analyzed using an Ion Chromatagraph (IC) and reactive silicate via colorimetric methods. Mean leachate Ca:Cl^- ratio (in equivalents) of cryoconite and western glacial surface sediments was 4.0 after just 30 minutes. The largest gains occurred between 8 and 24 hours from 5.5 to 11.0. Proglacial stream sediments had greater initial reactivity (19.4) but ratios decreased from peak values at 24 hours (10.4). Greater overall Si:Cl ratios occurred in the glacier surface samples (dry sediment, and cryoconite) than Andersen Creek, but all types increased ratios through time. Mean NO₃^-:Cl^- ratios were much lower in the wet sediment from the cryoconite holes (0.0083) and Andersen Creek (0.0058) than the glacier surface sediments (0.10), and all behaved dynamically through time. The consequences for bioavailability from these and beach sediments will be discussed.