CGRG Bibliography of Canadian Geomorphology
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Author : Gottesfeld, A.S.
Date : 1999
Title : Tunnel valleys and eskers west of Prince George, British Columbia.
Publication : Program and Abstracts. 42nd Annual Meeting of the Western Division of the Canadian Association of Geographers, Okanagan University College, Kelowna, British Columbia, March 11 to 13, 1999.
Issue :
Page(s) :
Abstract
Late in the Fraser deglaciation, 11ka-10ka BP, large proglacial lakes collected melt water on the Nechako Plateau. These lakes were connected by sub-ice tunnel valleys which directed flow over shallow divides. The upstream portions of the tunnel valleys are approximately 60m deep and 1 to 1.5 km wide. Sedimentation was concentrated in the downstream portions of the tunnel valley systems, and formed braided esker complexes. Crudely statified, matrix-supported gravels were deposited to form these eskers. The delta zone is composed of alternating gravel beds, diamictons, interpreted as sub-aqueous debris flows, and silt/sand rhythmites. The depositional zones in the receiving lakes have thick sand deposits formed around stranded icebergs. The braided eskers may be multi-year deposits, with subsequent fills being deposited alongside earlier frozen contributions. Their poorly sorted sandy gravels are consistent with pipe flow. Two tunnel valley/esker complexes west of Prince George are particularly interesting. The channel system occupied by Cluculz and Bednesti Lakes and that occupied by Norman and Dahl Lakes. These two channels formerly connected ice bounded Glacial Lake Vanderhoof and Glacial Lake Fraser. Channel dimensions and calibre of transported gravels in the Norman Lake Channel permit an estimate of the flow rate: >181,000 m3/sec. This discharge is about ten times the current peak flood rate of the Fraser River at Mission and in the range of the largest rivers now active. The flow of the larger channel system at Cluculz Lake would have been larger. .
Bibliography of Canadian Geomorphology