CGRG Bibliography of Canadian Geomorphology
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Author : Froese, D.; Doupe, J.P.; Sanborn, P.; Murton, J.; and Kennedy, K.
Date : 2011.
Title : Plio-Pleistocene drainage of Northern Yukon and the Mackenzie delta: Detrital zircons, glacial diversions and periglacial modification of a fluvial landscape.
Publication : Joint Annual Meeting of Geological Association of Canada, the Mineralogical Association of Canada, the Society of Economic Geologists and the Society for Geology Applied to Mineral Deposits. May 25-27, 2011. University of Ottawa, Ottawa, Ontario.
Issue :
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Abstract
Paleodrainage of northern Yukon is generally thought to have been ancestral to the Mackenzie River, flowing across (or through) the present day Richardson Mountains; only diverted into the Yukon River by the latest Pleistocene Laurentide Ice Sheet. Here, we investigate northern Yukon drainage using geomorphology, stratigraphy and sedimentology, along with (206Pb/238U) detrital zircon chronologies, to reconstruct paleodrainage across the region. Easterly paleoflow directions are associated with Pliocene gravels in the Old Crow basin and dominated by late Devonian age zircons (ca. 350-400 Ma) reflecting ages associated with the Old Crow intrusions. Antecedent drainage across the Richardson Mountains is suggested by the Bell and Rat River valley system which includes large terraces more than 100 m above the modern valley floor. In general these terraces, likely dating to the Pliocene, have been stripped of their fluvial cover by cryopedimentation processes, but large fluvial gravels are present along the terrace margins. Samples of fluvial sand from one large terrace and the modern Bell River are similar to a sample from a terrace along the Rat River, all dominated by North American continental zircon ages with a secondary population between 300 and 600 Ma. The late Devonian ages from the Old Crow batholiths are muted and appear to be overwhelmed by local sediment contributions from North American margin rocks making up the Richardson Mountains. Samples from the modern Mackenzie River and the Late Pleistocene Kidluit Formation (ca. 50,000 years BP) are remarkably similar, featuring broad North American continental ages, with a prominent peak in the mid to late Mesozoic. These ages suggest that the Mackenzie River system was in its present position by at least this time.
Bibliography of Canadian Geomorphology