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HR: 10:20h
AN: P22A-01
TI: Debris-Covered Glaciers in Antarctica: Analogs for Viscous-Flow Features on Mars
AU: * Marchant, D R
AF: Department of Earth Sciences, Boston University, 685 Commonwealth Avenue, Boston, MA 02215, United States
AU: Phillips, W M
AF: University of Idaho, Idaho Geological Survey, Moscow, ID 83844, United States
AU: Schaefer, J
AF: Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY 10964,
AU: Fastook, J
AF: University of Maine, Climate Change Institute, Orono, ME 04469,
AU: Landis, G
AF: U.S. Geological Survey, Denver Federal Center, Denver, CO 80225, United States
AB: The McMurdo Dry Valleys (MDV) are generally classified as a hyper-arid, cold-polar desert. Subtle variations in climate parameters throughout the region result in considerable differences in the distribution, origin, and morphology of buried ice. In the coastal thaw zone, near-surface buried ice experiences seasonal melt and may have formed where pore water from surface snowmelt freezes underground (segregation ice). Characteristic landforms associated with this type of buried ice include thermokarst, shallow planar slides, and solifluction. In contrast, in the coldest and driest regions of the MDV, the stable upland zone, there is insufficient meltwater to produce extensive segregation ice. Rather, widespread buried ice in this zone is typically glacier ice. Temperature data indicate that ice remains frozen in this zone if buried beneath ~15 cm of debris. The Mullins-valley debris-covered glacier, which lies within the stable upland zone, contains ancient glacier ice beneath a thin layer of sublimation till. Four independent dating techniques confirm that the glacier age ranges from ~10 ka near the valley head, to >8 Ma at its diffuse terminus in central Beacon Valley. The dating methods include cosmogenic-nuclide analyses of surface boulders; horizontal ice-flow velocities as determined from synthetic aperture radar interferometry; 40Ar/39Ar analyses of in-situ ash fall in relict polygon troughs at the till surface; and numerical ice-flow models. Age results so derived are in accord with measured variations in ancient community DNA extracted from pristine ice samples along the length of the glacier. Multi- channel seismic and ground-penetrating radar surveys demonstrate that the ice is relatively clean and that it averages from ~45 m to ~150 m thick. Morphologic comparisons of the Mullins Valley debris-covered glacier are used to shed light on the origin and modification of near-surface ice on Mars.
DE: 5415 Erosion and weathering
DE: 5416 Glaciation
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting

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