ICE-CORED LOBES IN CENTRAL TAYLOR VALLEY, ANTARCTICA: ORIGIN AS REMNANT BURIED GLACIAL ICE

A recent theme in geomorphological research is to understand the age, origin, and modification of buried-ice deposits in polar latitudes. One application of these investigations has been to understand the climatic significance of debris-covered glaciers in Antarctica, some of which may contain ice of late Miocene age. A related inquiry, presented here, is to examine buried-ice deposits, common throughout the McMurdo Dry Valleys, whose origin and style of degradation is not yet well understood. We investigate a 2-km-long ice-cored lobe (East Stocking Lobe or ESL) along the north wall of central Taylor Valley. On the basis of integrated analyses, we show that the ESL is cored with remnant glacier ice, most probably derived from an advance of nearby Stocking Glacier ~ 130 kyr BP. Seismic data, coupled with results from ice-flow modeling, suggest that the buried core of glacier ice is < 30 m thick. Near its terminus, the ESL flows at a rate of ~ 2.4 to 6.7 mm/a. The loose drift that caps the buried ice (typically < 1 m thick) is composed of moderately stratified sand- and gravel-sized clasts. Stable isotopic analyses of samples from the upper 30 cm of the buried ice lie on a slope of ~ 5.8 (when plotted on a dD vs. d18O graph), suggesting modification by freeze/thaw processes and evaporation/sublimation. Measured air and soil temperatures show that intermittent melting is most likely possible during summer months where buried ice is ≤ 35 cm below the ground surface. Morphological comparisons with ice-cored deposits in upland regions of the Dry Valleys, such as Mullins and Beacon valleys (30 km inland and 500 m higher in elevation), and near the coast (40 km distant and 500 m lower in elevation) reveal marked contrasts in the style of near-surface ice degradation and cryoturbation. From these morphological comparisons, we infer that buried-ice deposits in the high-elevation sector of the Dry Valleys have not experienced the relatively warm climate conditions now found at the ESL (e.g., sustained summer temperatures of ≥ –4ºC) for the last several million years.