HR: 0800h
AN: C41A-0044    [Abstracts]
TI: Studies of contemporary glacier basal ice cryostructures to identify buried basal ice in the permafrost: an example from the Matanuska Glacier, Alaska.
AU: * Stephani, E
EM: fseas15@uaf.edu
AF: Institute of Northern Engineering and Department of Civil and Environmental Engineering, University of Alaska Fairbanks, P.O. Box 775 900, Fairbanks, AK 99775-5900, United States
AU: Fortier, D
EM: ffdf@uaf.edu
AF: Institute of Northern Engineering and Department of Civil and Environmental Engineering, University of Alaska Fairbanks, P.O. Box 775 900, Fairbanks, AK 99775-5900, United States
AU: Kanevskiy, M
AF: Institute of Northern Engineering and Department of Civil and Environmental Engineering, University of Alaska Fairbanks, P.O. Box 775 900, Fairbanks, AK 99775-5900, United States
AU: Dillon, M
AF: Institute of Northern Engineering and Department of Civil and Environmental Engineering, University of Alaska Fairbanks, P.O. Box 775 900, Fairbanks, AK 99775-5900, United States
AU: Shur, Y
AF: Institute of Northern Engineering and Department of Civil and Environmental Engineering, University of Alaska Fairbanks, P.O. Box 775 900, Fairbanks, AK 99775-5900, United States
AB: In the permafrost, massive ice bodies occur as buried glacier ice, aufeis ice, recrystalized snow, massive segregated ice, injection ice, ice wedges or ice formed in underground cavities ("pool ice", "thermokarst-cave ice"). The origin of massive ice bodies in the permafrost bears considerable implications for the reconstructions of paleoenvironments and paleoclimates. Our work aims to help the permafrost scientists working on massive icy sediments to distinguish buried basal glacier ice from other types of buried ice. To do so, the properties and structure of contemporary basal ice must be well known. Field investigations at the Matanuska Glacier (Chugach range, South-central Alaska), consisted in descriptions and sampling of natural basal ice exposures. We have used the basal ice facies classification of Lawson (1979) which is simple, easy to use in the field and provides a good framework for the description of basal ice exposures. Cores were extracted and brought back to the laboratory for water and grain-size analyses. The sediments forming the cryostructure were mostly polymodal, poorly sorted gravelly silt to gravelly fine sand, with mud contents generally over 50%. These data will be used to calibrate three-dimensional (3D) models produced from micro-tomographic scans of basal ice which will produce quantitative estimates of volumetric ice and sediments contents of basal ice cryostructures. Ultimately, visual qualitative and quantitative characterization of the basal ice components of 3D models together with field observations and laboratory analysis will allow for a new micro-facies and cryostructures classification of the basal ice. Our work will also have applications in glaciology, glacial geology, geomorphology, Quaternary and paleo-climatological studies based on inferences made from the structure of basal glacier ice. This paper presents the internal composition of the basal ice facies in terms of cryostructures assemblages (Fortier et al.: 2007) and sedimentological properties. Fortier, D., Kanevskiy, M, Stephani, E., Dillon, M., Shur, Y. 2007. Facies and cryostructures of glacier basal ice as an object of permafrost study, an example from the Matanuska Glacier, Alaska. Canadian Quaternary Association Conference, Ottawa, June 2007: 75. Lawson, D.E. 1979. Sedimentological analysis of the western terminus region of the Matanuska Glacier, Alaska. Cold Regions Engineering and Research Laboratory, Hanover, N.H., Report 79-9.
DE: 0702 Permafrost (0475)
DE: 0720 Glaciers
DE: 0770 Properties
SC: Cryosphere [C]
MN: 2007 Fall Meeting