Abstract: he bedrock geology in the Mount Decoeli area of southwest Yukon is characterized by Paleozoic to Triassic stratigraphy of the Alexander terrane, Wrangellia and the Bear Creek assemblage, overlain and intruded by Jurassic and younger rocks. Alexander terrane rocks comprise mainly Devonian mafic to intermediate volcanic and volcaniclastic rocks overlain by thick successions of carbonate and phyllite. Wrangellia is characterized by Mississippian to Permian volcanic and siliciclastic rocks of the Station Creek and Hasen Creek formations, overlain by Upper Triassic basalts and calcareous rocks of the Nikolai and McCarthy formations respectively. The Alexander terrane and Wrangellia are separated by the Duke River fault, a mainly Late Cretaceous northeast-verging thrust fault. To the northeast, Wrangellia is separated from the Bear Creek assemblage by the Denali fault, a strike-slip fault with as much as 400 km of right-lateral motion.
The Bear Creek assemblage comprises metamorphosed and deformed siltstone, mudstone and sandstone interlayered with mafic to intermediate volcanic and volcaniclastic rocks. Preliminary ages suggest the Bear Creek assemblage is Late Triassic (ca. 204 Ma). Regional correlation of the Bear Creek is unclear, but similarities between the assemblage and rocks of the Taku and Alexander terranes suggest possible linkages. Correlation with Upper Triassic rocks of Wrangellia is less favourable.

Authors: Israel, S., Colpron, M., Cubley, J., Moynihan, D., Murphy, D.C. and Relf, C.

NTS Mapsheet(s): 115A12, 115A13, 115B09, 115B16

Citation: Israel, S., Colpron, M., Cubley, J., Moynihan, D., Murphy, D.C. and Relf, C., 2015. The Bear Creek assemblage: A latest Triassic volcano-sedimentary succession in southwest Yukon. In: Yukon Exploration and Geology 2014, K.E. MacFarlane, M.G. Nordling and P.J. Sack (eds.), Yukon Geological Survey, p. 99-112.

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