CGRG Bibliography of Canadian Geomorphology
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Author : Froese, D.G.; Smith, D.G.; and Reyes, A.V.
Date : 2010.
Title : Revisiting the northwest outlet of Glacial Lake Agassiz: catastrophic floods, permafrost and mega-deltas.
Publication : WDCAG 2010: A Spatial Odyssey. 52nd Annual Meeting of the Western Division of the Canadian Association of Geographers. March 25-27, 2010. University of Alberta, Edmonton, Alberta.
Issue :
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Abstract
We revisited the stratigraphy of exposures along the Athabasca valley associated with new aggregate development for several oilsand extraction sites, and exposures along the lower Athabasca River. We recognize five fluvial units in the valley: (1) a pre-Laurentide Athabasca River gravel deposited prior to advance of the Laurentide Ice Sheet; (2) immediately post-glacial Athabasca river gravels; (3) catastrophic flood boulder-gravel associated with the Clearwater spillway; (4) sandy braided river-Agassiz-draining discharge into the Athabasca following flood sedimentation; and (5) fluvial-deltaic sedimentation on the lower Athabasca into glacial Lake McConnell. Radiocarbon ages on mammoth bones and wood suggest a mid-Wisconsinan age for unit 1. Luminescence ages indicate that units 2 and 3 date to the latest Pleistocene, but the associated errors on these latter ages are too large to address the YD question. However, the surface of Unit 4 includes rare periglacial structures, including ice wedge casts and involutions on their surface, suggesting that climate was sufficiently cold when the NW outlet was active to have active permafrost, presumably extending into the latest Pleistocene. New radiocarbon ages on plant macrofossils, including Picea logs with fine branch preservation, within deltaic sediments, show impacts of bitumen contamination on many samples, which we removed using organic solvents in a soxhlet apparatus. Reliable ages from Picea macrofossils from within the delta date to ca. 10,000 14C yr BP and post-date the catastrophic flooding of the outlet. If we assume a period of ecesis and estimate the age of trees, it suggests the outlet was active during latest YD time, but it is still unclear if flood initiation was associated with the beginning of the YD.
Bibliography of Canadian Geomorphology