ABSTRACT: Surficial geology, till geochemistry and drift prospecting in the Bonokoski Lake Area (NTS 64M-11, -12, -13, and -14), Northeastern Saskatchewan.

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Quaternary surficial geological mapping at a 1:100,000 scale, and till sampling were initiated this past summer (2001) in the Bonokoski Lake area (64M-11, -12, -13, and -14), as part of the multidisciplinary, multi-year Phelps Lake Project in the far northeastern corner of Saskatchewan. Glacial drift cover is extensive in this region, with less than 10 percent exposed bedrock overall. This project is designed to update the geological database and assess the mineral potential of this poorly understood portion of the province. Multiple ice flow directions were documented in the area with the dominant direction being to the south-southwest (averaging 210 degrees). Till, boulder fields and organic terrain are the dominant surface materials. There are several substantial sand and gravel deposits associated primarily with large esker-kame complexes. Enormous erratics were observed at a number of locations. The dominant glacial landforms are ground moraine, stagnant ice moraine, recessional moraines, ridged moraine and drumlins. Six large esker systems cross the map area, predominantly associated with subglacial channels. Felsenmeers and short-travelled glacial boulder or block fields are characterised by predominantly monolithologic, angular boulders of similar size, typically 1 to 2 m in diameter. Change in the rock type of the boulders generally corresponds to change in underlying or nearby bedrock. The greatest abundance of these block fields overlies granitic terrain. The dramatic landscape of Bonokoski Lake area is primarily a product of deglaciation during the retreat of the Late Wisconsinan ice sheet. Recessional moraines, stagnant ice moraine and well-developed esker systems are evidence of a slowly retreating ice margin. Deglaciation appears to have been dominated by periods of stagnation and downwasting interspersed with seasonal pulses of the ice margin. Downwasting would have produced abundant meltwater, which drained subglacially towards the ice margin both as high volume, turbulent sheet floods, and through large subglacial channels. In general, the regional till geochemistry reflects the regional bedrock geology. An area of elevated concentrations of base metals (Cu, Zn, Ni, Pb) related to mafic volcanic - siliceous iron formation unit was delineated in the till in the vicinity of Bonokoski Lake. Elevated gold values were found in till in the Milton Lake area. Mineralised boulders (base metals and gold) were found in numerous locations including the Hatle Lake area, a known area of gold deposits. These findings suggest that both till sampling and boulder prospecting would be effective methods of prospecting in this region.

Bibliography of Canadian Geomorphology