CGRG Bibliography of Canadian Geomorphology
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Author : Froese, D.G.; Barendregt, R.W.; Duk-Rodkin, A.; Enkin, R.; Hein, F.J.; and Smith, D.G.
Date : 1997.
Title : A reconstruction of Pliocene-Pleistocene tectonics and climate, Lower Klondike Terraces, Dawson area, Yukon
Publication : Beringia Paleoenvironments Workshop Sept., 1997: Abstracts and Program. Edited by: Scott Elias and Julie Brigham-Grette . Workshop sponsored by the U.S. National Science Foundation.
Issue :
Page(s) : 42.
Abstract
The lower Klondike valley and its gold-bearing tributaries, Bonanza and Hunker creeks, west-central Yukon, contain some of the best preserved and exposed late Pliocene to early Pleistocene sediments in the Canadian Cordillera. In this study, sedimentologic and paleomagnetic evidence is used to present a summary of depositional environments correlated to the geomagnetic polarity time scale. In Pliocene pre-glacial times, gold bearing tributaries of the Klondike River, Bonanza and Hunker creeks, deposited the White Channel gravel in response to active tectonics as braid river alluvial fans with repeated cycles of aggradation and incision during the late Gilbert (?) and Gauss chrons. Climatic cooling in the late Pliocene resulted in White Channel aggradation and the first evidence of periglacial conditions (ice wedge growth). Synchronous with alluvial aggradation in the unglaciated tributaries, and interfingering with distal upper White Channel gravel, the ‘Klondike Wash’ gravel records the first proglacial outwash in the Klondike valley during the late Gauss (magnetically normal > 2.6 Ma). This outwash can be traced southeast to the Tintina Trench and was the result of the first late Pliocene advance of the northern Cordilleran Ice Sheet, rather than local piedmont glaciers. An intermediate terrace in the Klondike valley indicates three successive depositional environments: first, a lowermost interglacial wandering gravel bed river sequence; second, deposition of a proximal braided river assemblage, indicating aggradation during a pre-Reid glacial event followed by incision of the terrace level; and third, beginning of aeolian-colluvial deposition. Paleomagnetic results of these previously unreported loess, re-worked loess and paleosols provides a limiting chronology for the upper terrace level, and indicates deposition through much of the Matuyama (2.6-0.78 Ma) and Brunhes (<0.78 Ma) chrons, suggesting the dominance of katabatic winds in this area of Beringia during the early to middle Pleistocene. By Reid time, ca. 200 ka, the lower Klondike River and its tributaries were near their present position.
Bibliography of Canadian Geomorphology