Abstract: Throughout the Pleistocene epoch, Yukon was repeatedly influenced by glacial ice originating from the Cordilleran Ice Sheet and independent alpine glaciers. The penultimate limit in Yukon has garnered controversy in recent years, as moraines in the central region of the territory were found to be older (MIS 6) than moraines in the southwest part of the territory and Alaska (MIS 4). The Ogilvie Mountains, located east of Dawson City, have proven especially problematic for chronological studies. This study will attempt to test a relatively new dating method on penultimate surfaces in the Ogilvie Mountains; Chapman Lake is the primary study area. Using a vertical sampling method to construct a cosmogenic depth versus concentration profile in outwash gravel, this research will determine whether Marine Isotope Stage 4 or 6 provided the conditions necessary for ice nucleation to build the penultimate glacial surface. The age calculated by the depth profile is supported by radiocarbon ages and macrofossil samples, optically stimulated luminescence ages, TCN boulder dating, as well as detailed stratigraphy of significant sites near the Chapman Lake moraine. The results will help determine the effects of climate forcing in this region and its relationship to the existing glacial framework of the territory.

Authors: Brown, L., Ward, B., Bond, J.D. and Gosse, J.

NTS Mapsheet(s): 116B09, 116B16

Citation: Brown, L., Ward, B., Bond, J.D. and Gosse, J., 2015. Using terrestrial cosmogenic nuclides to constrain timing of penultimate ice advance in the Ogilvie Mountains, Yukon. In: Yukon Exploration and Geology 2014, K.E. MacFarlane, M.G. Nordling and P.J. Sack (eds), Yukon Geological Survey, p. 17-27

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