CGRG Bibliography of Canadian Geomorphology
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Author : Easterbrook, D.J.; and Kovanenc, D.J.
Date : 2005
Title : Comments on “Marine and limnic radiocarbon reservoir corrections for studies of late- and postglacial environments in Georgia Basin and Puget Lowland, British Columbia, Canada and Washington, USA” by Hutchinson et al. 2004, Quaternary Research 61, 193–203.
Publication : Quaternary Research
Issue : 63(2):
Page(s) : 224-226.
Abstract
Hutchinson et al. (2004) discuss marine reservoir corrections for shells in the Georgia Basin and Puget Lowland of British Columbia and Washington State. To explain the spatial variations of the marine reservoir value, Hutchinson et al. concluded that late-glacial, isostatic depression of the coastal area may have promoted deep-water exchange between the Pacific Ocean; that these inland seas led to larger reservoir ages (about -950 ± 50 yr); and that sites in sheltered locations yield much higher mean oceanic reservoir corrections (-1200 ± 130 yr), possibly as a result of reduced ocean ventilation under seasonal sea ice and local influxes of 14C-depleted glacial meltwater. We wish to expand the discussion here because, despite their compiled data, a dynamic model to explain the spatial variability of the marine reservoir values seen in this region remains difficult to demonstrate. Based on the comments above, the Hutchinson et al. scenario linked to local influxes of 14C-depleted glacial meltwater and reduced ocean ventilation under seasonal sea ice to explain the spatial variability of the marine reservoir value seen in this region has not been demonstrated. More likely is that part of the spatial variability of the marine reservoir values result from variable 14C contents in surface water, ocean-atmosphere CO2 exchange, fresh water inputs, coupled with changes in the atmospheric radiocarbon concentration (Stuiver and Braziunas, 1993 and Delaygue et al., 2003). Regional or local reservoir ages may not have always varied in parallel, especially at coastal sites with varying fresh water input and upwelling. We believe that additional data are needed to adequately demonstrate which of the possible causes of the larger Pleistocene marine reservoir values is truly responsible. At present, with only our six shell/wood pairs, plus two from the Saanich Inlet core and Furry Creek, the data are insufficient to prove a single cause for the higher reservoir values. Improving the spatial resolution of independently determined marine reservoir ages will aid studies that link past climatic, glacial, and oceanographic changes.
Bibliography of Canadian Geomorphology