Abstract: The Middle–Upper Devonian Canol Formation is the focus of a new study by the Yukon Geological Survey in north Yukon. Fieldwork in summer 2013 involved locating, measuring, and sampling Canol Formation strata in the Richardson and northern Ogilvie mountains. In June, 229 m of Canol Formation strata were measured on the Trail River, eastern Richardson Mountains (NTS 106L/6). The Canol Formation at this location is entirely exposed, except for ~2 m at its upper contact with the overlying Imperial Formation. On Trail River, the Canol Formation is a resistant, silica-rich unit that is characterized by rhythmically bedded siliceous shale and chert comprising four lithofacies: 1) siliceous shale; 2) chert; 3) siliceous shale (>50%) and chert (10-50%); and 4) chert (>70%) and siliceous shale (10-30%). Siliceous shale is fissile, finely laminated in beds up to 10 cm thick, and may be either soft and recessive or hard and resistant. Chert exhibits conchoidal fracture and occurs in beds up to 16 cm thick. Both shale and chert are black in color on fresh surfaces, and weather grey to black, olive grey, brown with a distinct yellowish orange, dark red, and/or very minor apple-green weathering residue. The lower contact of the Canol Formation with Road River Group calcareous shale is sharp, and marked by a concretionary bed overlain by a thin (<1 m) weathered mineralized zone. This mineralized zone may be in-part correlative with the Ni-Zn-PGE “Nick” horizon observed in the region. A marked lithology change occurs from the Canol to the Imperial formation which consists of weathered mudstones with a significantly lower silica content. Concretions up to 2.5 m long were observed in the Canol Formation but possible fossils were only observed at two locations where unidentified impressions on a bedding surface could be biological (or mineralogical). Fine-grained pyrite occurs throughout the formation, either as disseminated grains, in thin laminations (mm-scale), and rarely in concretionary horizons. The sampling program involved spectral gamma-radiation readings at one-metre intervals, and chip samples through two-metre intervals for Rock-Eval/total organic carbon (RE/TOC) and inductively coupled plasma-emissions/mass spectroscopy lithogeochemistry (ICP-ES/MS). Targeted samples for microfossil biostratigraphy, vitrinite reflectance, and XRD mineralogy were also collected. Laboratory results are anticipated in 2014.

Authors: Fraser, T.

NTS Mapsheet(s): 106L06

Citation: Fraser, T., 2014. Field descriptions of the Middle-Upper Devonian Canol Formation on Trail River, east Richardson Mountains, Yukon. In: Yukon Exploration and Geology 2013, K.E. MacFarlane, M.G. Nordling and P.J. Sack (eds.), Yukon Geological Survey, p. 53-68.

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