Soil Processes on Delta and Till Deposits in Taylor Dry Valley, Antarctica

During the Last Glacial Maximum the West Antarctic Ice Sheet expanded across McMurdo Sound and dammed Taylor Valley. It is speculated that this ice dam caused the formation of proglacial Lake Washburn, which reached an elevation of approximately 300 meters above sea level. Inundation by the lake would leach Taylor Valley soils of soluble salts, and present soil salt contents should reflect accumulation since the last flooding event. Interpreting soil soluble salt content requires an understanding of active soil forming processes in the Dry Valleys and how these processes affect salt distribution and accumulation. Our findings indicate that the soil salt contents are highly correlated with fines brought in by eolian processes. The desert pavement surface traps windblown clay- and silt-size particles, along with salts, to accumulate at the soil surface. Both the fines and salts appear to be transported to depth in the soil profile by periodic wetting events and cryoturbation, thereby resulting in the accumulation of fines and salts in the upper soil horizons. Soil salt contents parallel the % volume of fines in the upper horizons of soils, and soil salt contents increase with decreasing elevation, a trend that mirrors higher fluxes of eolian material at lower elevations due to wind speed, availability of material for transport, and settling. These results indicate that variables affecting eolian deposition, such as topography and wind patterns, influence the rate of salt accumulation in Taylor Valley soils. This makes it difficult to determine a detailed lake level history of Lake Washburn by looking at soil salt contents. A sharp increase is observed in the soil soluble salt content above 300 meters above sea level, but this may simply reflect an older till deposit rather than a previous lake shoreline. Further consideration of sample locations and controls on eolian input is in progress to refine the relative age estimates.