Abstract: We present new field and whole-rock geochemical data from the type section of the Triassic Jones Lake Formation (JLF) located along the Yukon-Northwest Territories border in the Nahanni map area (NTS 105I/13). The type section is the first location of a regional-scale study that investigates the nature of Triassic siliciclastic rocks, and tests the presence of an overlap assemblage linking pericratonic terranes with North America by the Triassic, instead of Early to Middle Jurassic. The JLF is composed of carbonaceous shale and ripple cross-laminated calcareous sandstone thought to be associated with the Cordilleran miogeocline, and is devoid of sediment sourced from terranes to the west. Whole-rock shale geochemistry has provided evidence that the JLF is distinguishable from the underlying Mount Christie Formation and has trace and rare earth element concentrations that are most similar to old continental crust. However, the JLF does contain geochemical signatures suggestive of a minor mafic component.

Authors: Beranek, L.P. and Mortensen, J.K.

Keywords: Jones Lake Formation, Mount Christie Formation, whole-rock geochemistry

NTS Mapsheet(s): 105I13

Citation: Beranek, L.P. and Mortensen, J.K., 2006. Triassic overlap assemblages in the northern Cordillera: Preliminary results from the type section of the Jones Lake Formation, Yukon and Northwest Territories (NTS 105I/13). In: Yukon Exploration and Geology 2005, Emond, D.S., Bradshaw, G.D., Lewis, L.L., and Weston, L.H. (eds.), Yukon Geological Survey, p. 79-91.

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