CGRG Bibliography of Canadian Geomorphology
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Author : Froese, D.G.; and Hein, F.J.
Date : 1997.
Title : An interglacial placer deposit setting : a lesson from the Klondike area
Publication : 1997 Geoscience Forum, Yukon Chamber of Mines, Nov. 25, 1997, Whitehorse, Yukon
Issue :
Page(s) :
Abstract
An intermediate level terrace near Dawson City was recognized to contain significant economic concentrations of placer gold in the late 1980s. Regional surficial mapping has shown the distribution of many high level terraces of pre-Reid, Reid and McConnell age in central Yukon, but the relationship between economic gold concentration and terraces is not well understood. Sedimentological study of an intermediate level terrace near Dawson City suggests two river types have been dominant: the first, a 'wandering gravel bed river' is characterized by moderate sinuosity, lateral accretion deposits, limited sand facies, and generally fine gravel; the second, 'proximal braided river' is characterized by multiple channels, very thick and crudely imbricate gravel, low bed relief, and a greater than 100% increase in maximum particle size from the lower wandering gravel bed river deposit. The gold-bearing 'wandering gravel bed river' assemblage is typical ofpresent-day conditions with river processes dominated by lateral migration and high gravel transport rates through the system conducive to heavy mineral concentration during an interglacial period. The 'proximal braided river' is characteristic of nearby glacial ice and rapid sedimentation resulting in poor heavy mineral concentration. The transition from a wandering gravel bed river to a proximal braided river is suggested to mark the onset of a pre-Reid glaciation in the Southern Ogilvie Mountains. The sedimentology of the intermediate terrace gravels suggest a geomorphic model which may be used for exploration of terrace placer deposits in central Yukon with a similar pattern of regional glaciation influencing terrace formation.
Bibliography of Canadian Geomorphology