HR: 0800h
AN: C51A-0271    [Abstracts]
TI: Late Miocene-Pleistocene Stability of upper Ferrar Glacier, Dry Valleys, Antarctica
AU: * Staiger, J W
EM: jane.staiger@gmail.com
AF: National Center for Earth-surface Dynamics, University of Minnesota-Twin Cities St. Anthony Falls Laboratory, Minneapolis, MN 55414 United States
AU: Marchant, D R
EM: marchant@bu.edu
AF: Department of Earth Sciences, Boston University, Boston, MA 02215 United States
AU: Schaefer, J M
EM: schaefer@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964 United States
AU: Johnson, J V
EM: johnson@cs.umt.edu
AF: Department of Computer Science, University of Montana, Missoula, MT 59812 United States
AU: Oberholzer, P
EM: oberholzer@erdw.ethz.ch
AF: Baugeologie und Geo-Bau-Labor, Quaderstrasse 18, Chur, 7000 Switzerland
AB: Vernier Valley (78^o S, 161^o E) opens onto a peripheral lobe of upper Ferrar glacier in the Dry Valleys of southern Victoria Land, Antarctica. The areal distribution of Ferrar drifts, along with a relative and numerical chronology afforded by surface-weathering characteristics and ³He - ²¹Ne exposure-age data, are used to reconstruct the Late Miocene-to-Pleistocene history of upper Ferrar Glacier. Applying a modest erosion rate correction of 10 cm Ma^-1, our results show that the glacial record provided by Ferrar (1, 2, 3, and 4) drifts in Vernier Valley extends back into late Miocene time. Cosmogenic ages for clasts on the modern, ice-cored Ferrar 1 moraine suggest that nuclide inheritance is negligible. The development of weathering pits and desert varnish on surface cobbles varies linearly with cosmogenic age. Ice-surface profiles reconstructed from the moraine distribution and exposure-ages of boulders atop the moraines indicate that the ice-surface elevation of upper Ferrar Glacier has lowered roughly 50 m throughout the Quaternary Period and roughly 125 m since late Miocene time. Conversely, during MIS 2, the ice-surface elevation of upper Ferrar Glacier was likely no higher than today and may have been below modern levels. The moraine now forming through ice sublimation and debris accumulation at the modern, cold-based Ferrar Glacier margin is texturally similar to older drifts up-valley. The slow recession of cold-based glacier ice (and without surface melting ablation zones) in lower Vernier Valley implies enduring cold-desert conditions, much like those of today, for at least the last ~6.5 Ma. Results from a 2-D glacier flow-band model also demonstrate that upper Ferrar Glacier lacked basal-melting zones even during the Pliocene optimum. The overall stability of this glacial system has implications for the response of ice in this sector of Antarctica to future polar warming.
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0798 Modeling
DE: 1130 Geomorphological geochronology
DE: 1150 Cosmogenic-nuclide exposure dating (4918)
SC: Cryosphere [C]
MN: Fall Meeting 2005