CGRG Bibliography of Canadian Geomorphology
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Author : Francus, P.; Abbott, M.; Bradley, R.; Keimig, F.; Perren, B.; and Patridge, W.
Date : 2000.
Title : An annual snow melt intensity record in lacustrine sediments of Sawtooth Lake, Arctic Canada.
Publication : 30th International Arctic Workshop, Program and Abstracts, 2000. Institute of Arctic and Alpine Research, University of Colorado at Boulder
Issue :
Page(s) : 62-63.
Abstract
Sawtooth Lake, Ellesmere Island (79° 20’ N, 83° 51’ W), contains annual clastic laminations in its deep distal basin: coarse and fine silt sediment during the snow melting season, followed by the settling of clays during the ice covered winter season. We present preliminary results obtained using an image analysis technique that provides multivariate quantified data for each varve. Petrographic and backscattered electron microscope micrographs of thin-sections are processed to produce black and white images, where white pixels represent the clay-rich sedimentary matrix and black pixels represent particles in the matrix: silt- or sand-sized, terrigenous or authigenic particles, diatoms or organic debris (Francus, 1998). Computer-assisted measurements of the size, shape, orientation and packing of the particles forming the varves allow for their multivariate quantification. Present day on-site meteorological, hydrological and sedimentological studies have been used to understand how the climatic signal is recorded in the varved sediments. The value of this has been demonstrated in our previous work, leading to more confidence in the underlying controls on sediment flux and varve formation in the lakes (Bradley et al., 1996). The data obtained on each single varve of the uppermost sections of the cores have been compared with meteorological and climatological data, e.g. temperature, snow melt, wind, and discharge. From the Eureka metereological data set, we computed a snowmelt intensity index (SMI) for each year as the maximum snow depth decrease over a time period of 10 days. For the last 33 years, SMI correlates well with the median grain-size measured for each annual lamination. Lamination thicknesses do not correlate with mean summer temperature over the same period. Summer rain events are also recorded as thin beds of sand. The 90th percentile of the grain-size of each lamina detects and quantifies the intensity of those rain events. This comparison allows for the clarification of the climatic control on sediment fluxes to the lake and construction of a model linking sediment to climate. This model will be used to infer paleoclimate with annual resolution from downcore laminae.
Bibliography of Canadian Geomorphology