CGRG Bibliography of Canadian Geomorphology
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Author : Calvert, S.E.; Ivanochko, T.S.; and Pedersen, T.F.
Date : 2006.
Title : Stable isotope record of controls on Holocene organic matter accumulation in a British Columbia fjord.
Publication : Joint Annual Meeting of the Geological Association of Canada and the Mineralogical Association of Canada. University of Quebec in Montreal (UQAM) May 14-17, 2006.
Issue :
Page(s) :
Abstract
A 40 m piston core recovered from anoxic Effingham Inlet, B.C. reveals a record of organic matter accumulation during the late deglaciation and the Holocene in the northeastern temperate Pacific. Present-day seasonal diatomaceous production combined with terrestrial organic supply leads to the formation of annual laminae, which are preserved in the 10,000 year-long anoxic sediment record. Prior to 10,000 years B.P., sedimentation was dominated by glacial outwash clays and poorly sorted sands. The lamina record is occasionally interrupted by mass wasting events. The organic carbon isotope record shows that the Holocene section comprises a mixture of roughly one third marine planktonic organic matter and two thirds terrestrial material, using spring sediment trap and soil isotope ratios as end-members for marine and terrestrial contributions, respectively. Mass wasting intervals are dominantly terrestrial. Nitrogen isotope ratios are set by the dominant source of dissolved nitrogen for phytoplankton growth: isotopically heavy nitrate (from denitrification) from offshore sourced from the oxygen-deficient subsurface waters of the eastern tropical Pacific and carried to these latitudes by the California Undercurrent and eventually supplied to the inlet during periods of coastal upwelling; local supplies of nitrate altered isotopically in the subsurface anoxic waters of the inlet; and terrestrial nitrogen from vascular plant debris and soil particles. Correlation of isotopic and compositional records in the core identify time periods during which production and organic supply are dominated by offshore and local nutrient and organic sources over the last 17,000 years.
Bibliography of Canadian Geomorphology