CGRG Bibliography of Canadian Geomorphology
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Author : Chang, A.S.; Enkin, R.J.; Baker, J.; Dallimore, A.; and Thomson, R.E.
Date : 2006.
Title : Diatoms, laminated sediments, upwelling and rainfall records from AD 1947-1997, Effingham Inlet, Vancouver Island, Canada.
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 :
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Abstract
A 123-cm long freeze core was recovered in 1999 from the anoxic inner basin of Effingham Inlet (49°04.218' N, 125°09.429' W), west coast Vancouver Island, British Columbia. The chronology of the core was determined from varve counting, 137Cs dating and 210Pb dating of a 32-cm section of laminated sediments at the top of the core. Varves are dated from AD 1947 to 1997 above an ~85-cm thick landslide deposit interpreted to have been caused by the M = 7.3, June 1946 Comox earthquake. Varve thickness and the thickness of individual detrital and diatomaceous laminae were examined from X-ray photographs of the sediments. The thickness, density, and temporal structure of the dark winter detrital laminae correlate to regional rainfall records (daily and monthly). Diatom abundance was determined from 42 approximately annual subsamples, where the abundance is highest in 1956 and 1964, and is lowest from 1970-1972, with a recovery of diatom populations in the 1980s. The dominant species, Skeletonema costatum, blooms in the late spring. Thus, we compared the varve thickness and brightness to upwelling indices based on the strength of northwest winds during the months of May and June each year and found a weakly positive correlation. Through such calibrations, we are gaining insight into interpreting the climate record from a recently acquired 3-m long freeze core extending back 900 (14C) years, and the 40-m long MD02-2494 core extending back to the late Pleistocene.
Bibliography of Canadian Geomorphology