CGRG Bibliography of Canadian Geomorphology
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Author : Beierle, B.
Date : 1999.
Title : Revisiting Late Pleistocene glaciation in the Central Yukon Territory, Canada.
Publication : 1999 Fall Meeting of the American Geophysical Union, December 13-17, 1999 , San Francisco, California (abstract).
Issue :
Page(s) :
Abstract
New paleolimnological and geomorphic data from the Southern Ogilvie Mountains, Yukon Territory, Canada, suggest that at least some ice limits previously thought to be Reid age (MIS 8; >200,000 BP) may have been formed during the McConnell glaciation (MIS 2), challenging the accepted model of glaciation in northwestern North America and indicating the need for closer examination of glacial stratigraphy in this area. Fifty years of Quaternary stratigraphy has established a glacial chronology for the central Yukon characterized by three major glacial events of successively smaller extent. These glaciations are thought to have become progressively smaller as Quaternary uplift to the west intercepted increasing amounts of Pacific moisture, restricting precipitation in the interior and limiting local ice development. Three glaciations, the first of unknown age but thought to be early to mid Pleistocene in age, and two subsequent events during MIS 8 and MIS 2 are recognized in the region, but have only been chronologically constrained at two sites. Rates of incision derived from radiocarbon dating of lake sediment cores and aerial photograph interpretation and surficial mapping suggest that glacial valley fills and subsequent incision in at least two major river systems in the southern Ogilve Mountains, previously assumed to be Reid age (MIS 8; >200,000 BP), originated during the McConnell glaciation (MIS 2). Late glacial stream capture recorded in lake sediments indicates that significant incision in the Blackstone River valley could not have occurred prior to ca. 13,000 BP without destroying the lake from which the core was taken. This precludes the valley fill from having existed during MIS 7, 5 and 3 during which time more then 50 m of cumulative downcutting is recorded in the Stewart river system 100 km to the south. This reinterpretation of glacial limits suggests that in at least one case McConnell glaciation was more extensive than the Reid, with post-MIS 2 basal dates from other lake sediment core studies in the central Yukon suggesting this may be the case in other locations as well, and indicating a need for re-assessment of Quaternary events in the central Yukon Territory.
Bibliography of Canadian Geomorphology