CGRG Bibliography of Canadian Geomorphology
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Author : Friele, P.A.; Froese, D.; Smith, D.G.; Miskovic, A.; Jackson, Jr., L.E.; and Clague, J.J.
Date : 2001.
Title : Paraglacial sediment supply and eolian accumulation along the Yukon River during the Pleistocene-Holocene transition.
Publication : Canadian Quaternary Association/ Association canadienne pour l'etude du Quaternaire, Annual Meeting 2001. Whitehorse, Yukon Territory, August 20 – 24, 2001.
Issue :
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Abstract
Stratigraphic investigation of sediments exposed along the middle Yukon River indicate rapid accumulation of eolian sediments during the Pleistocene-Holocene transition. Radiocarbon ages from overbank sediments indicate that the Yukon River was at its present channel elevation by at least 10 000 14C years BP (10 ka), and subsequent floodplain aggradation was dominated by eolian accumulation. Localized blankets of fine sandy silt, 9-14 m thick, and eolian dunes have been identified along the Yukon River between the White River confluence and Steven’s Village, Alaska. Bedding is primarily horizontal planar to wavy. Interbeds of laterally extensive, organic-rich silt occur throughout. At White River confluence, the silts rest on channel gravel at river level, with radiocarbon ages indicating 12 m of eolian sedimentation between 9.5 and 9 ka. Twenty kilometers upstream of Fort Yukon, radiocarbon ages from the base of a large sand sheet/dune complex indicate accumulation began after 10.3 ka. Downstream, near Beaver, radiocarbon ages from the overbank/eolian contact range between 11.5 and 10.1 ka, and near Steven’s Village, they record aggradation between 9.8 and 9.3 ka, and prior to 7.5 ka. In each case, the surface soil associated with the eolian sediments is a weakly developed Brunisol, 30-40 cm thick, similar to the zonal soil of the region, suggesting little eolian sedimentation has occurred along the Yukon River floodplain since the early Holocene. Eolian activity occurred through the McConnell glaciation. The onset of deglaciation in the central Yukon and St. Elias Mountains began shortly after 13.5 ka, with the main retreat phase extending from 12.5-11.5 ka. Since glaciers were near their present extent before 10 ka, we discount the role of large-scale katabatic winds as the primary cause of eolian accumulations along the Yukon River floodplain in the early Holocene. Regional vegetation records indicate the development of forest by 8.5 ka in the interior of Yukon and Alaska with the transition to modern climate after 8 ka. Our data suggest that the paraglacial sediment flux to the Yukon River persisted through the early Holocene, contributing sediment for eolian accumulation along the floodplain. Further, the onset of significant accumulation correlates with the wane of meltwater discharge. The cessation of eolian accumulation is attributed to a decrease in paraglacial sediment flux and to the arrival of boreal vegetation, both contributing to a stabilization of the Yukon River floodplain by the early to mid Holocene.
Bibliography of Canadian Geomorphology