CGRG Bibliography of Canadian Geomorphology
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Author : Buffin-Bélanger, T.Hetu, B.; Savard, M.; Rousseau, G.; and Bibeau, P.
Date : 2007.
Title : Stratigraphy, sedimentology and palaeohydrology of a boreal forest environment from alluvial deposits along the Eastmain River, Québec.
Publication : CANQUA Ottawa 2007. Canadian Quaternary Association Conference, June 4-8, 2007. Carleton University, Ottawa, Ontario, Canada.
Issue :
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Abstract
Alluvial plains possess rich environmental records for which the potential has yet to be fully exploited in Quebec boreal forest environments. In this paper, we report the analysis of six alluvial sequences located along the Eastmain River, between PK231 and PK344. The six sequences are located on lower terraces that are 3 to 9 meters above the modern water level and their thicknesses ranged between 0.7 and 2.0 m. Stratigraphic and sedimentological analysis were conducted and 45 AMS radiocarbon dates were obtained from paleosols buried in the alluvial sequences. For one of the sequences, 20 AMS dates were extracted. The grain size distributions for all sequences are dominated by fine sand and silt forming compact layers and are described as overbank deposits. In two sequences, we encountered other deposits beneath the overbank materials; in one case cobbles and in another, coarse, stratified sands. The vertical accretion of the alluvial sequences started more than 4000 years BP and took place in a humid climatic period that is well documented for North America. From the radiocarbon dates, vertical accretion rates vary from 0.1 to 0.6 mm/year. The accretion rates vary with position along the Eastmain River. For the long sequence, a significant decrease in the accretion rate is evident in the last 2500 years. This decrease in accretion rate is correlated with an increase in the number of buried organic and Ae horizons. This suggest more frequent and longer periods of floodplain stability. The decreasing accretion rate is not solely due to less frequent flooding but can also be related to a diminution of sediment sources within the Eastmain river system.
Bibliography of Canadian Geomorphology