An overburden thickness model for Lac de Gras and Aylmer Lake, Northwest Territories, Canada

Abstract

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Much of northern Canada is covered by variable thicknesses of surficial sediment. Geological maps portray these sediments using subjective terminology such as till, marine sediments, esker or organics etc. surficial sediment and bedrock geology units are primarily derived from air photo interpretation. In the Lac de Gras and Aylmer Lake area of the Canadian Northwest Territories, there is limited primary depth-to-bedrock information, and thus a traditional overburden thickness model is difficult to acquire. A model can however be developed using inferred unit thickness information obtained from published 1:125,000 surficial geology maps and a digital elevation model. The modelling process is based on the construction of a bedrock elevation database that is subtracted from a digital elevation mode to provide an overburden thickness. The bedrock elevation database is derived by assigning each surficial unit an approximate thickness and subsequently subtracting this thickness from the each cell of the digital elevation mode. The resulting dataset represents a best approximation of the buried bedrock surface with a cell size determined by the digital elevation mode. This model may be used for a number of applications such as planning regional geophysical or geochemical surveys where data quality is affected by variable overburden thickness.