The Willow River area is underlain mainly by the Harveys Ridge succession of the Hadrynian to Paleozoic Snowshoe Group. This succession in general consists of black and grey siltite, micaceous quartzite, phyllite, limestone and minor dolostone (Geological Survey of Canada Memoir 421). Graphitic schist has been reported from early work in the area (Geological Survey of Canada Summary Report 1933A, pp. 32-33)