CGRG Bibliography of Canadian Geomorphology
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Author : Campbell, J.
Date : 2005.
Title : Field investigations of the Isle Brochet radioactive boulder trains, eastern Lake Athabasca (NTS 74O-SE05).
Publication : Summary of Investigations 2005, Saskatchewan Industry Resources, Miscellaneous Report
Issue : 2005-4.2. CD, Paper A-3.
Page(s) : 15 p.
Abstract
Extensive boulder prospecting during uranium exploration programs in the late 1960s and 1970s identified numerous radioactive boulder trains on the Athabasca Basin, some of which led to the discovery of significant uranium deposits (i.e., Key Lake). There remain, however, a number of “unsourced” boulder trains, particularly along the northern margin of the basin. This summer, preliminary investigations of two such boulder trains, the Jackfish and Wolfe boulder trains on Isle Brochet, Lake Athabasca, were carried out to assess the surficial geological context and assess their exploration potential. The boulder trains are primarily located on two very gently sloping, low relief bedrock ridges with thin glacial drift cover of <2 m. The ridges are overlain by a mixture of surficial materials that include a sandstone-rich, loose, sandy till capped by a boulder lag/or reworked till, cobble beaches composed primarily of flaggy sandstone blocks, and vegetation-concealed outcrop. The lowlands around the ridges are characterized by boulder lag, organic deposits, and winnowed silty, sandy till or matrix-rich clay-silt-sand diamicton. Rare, thin deposits of clayey silt do not mask the underlying till. In some places, the lowland surficial deposits have artificially defined the lateral extent of the dispersal trains. The trenches in the boulder train exposed three distinct till deposits. These include: a sandy, loose, meltout till; a hard, silty-sand subglacial till; and a less common, matrix-rich clay-silt-sand diamicton. Till deposit 2 commonly underlies till deposits 1 and 3. The tills were deposited on flaggy sandstone or sandstone bedrock. Cobble beach deposits and/or winnowed till with boulder lags typically overlie the tills. Lateral extent of the tills is unknown. The radioactive sandstone boulders are in the upper sandy till, but it has not been established if the lower silty-sand till also hosts radioactive detritus. The ice-flow history in this region is complex; the flow was initially to the south-southwest then it shifted westward during later stages. The main flow direction was to the southwest. Preliminary field work suggests the lower silty-sand and regional tills are related to the southwest ice flow. It is not certain if this same ice flow deposited the upper sandy till, and consequently the radioactive boulders, although the interpreted axes of the boulder trains trend southwest. This unit may have been deposited during the late stage westsouthwestward flow.
Bibliography of Canadian Geomorphology