Open File (English, PDF)

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Publisher-reported update

2026-08-26

Fenwick Creek (105D/3) and Alligator Lake (105D/6) map areas, located southwest of Whitehorse, Yukon, were mapped at 1:50,000 scale during the 1987 field season. The map areas are within the Teslin Plateau and the Boundary Ranges physiographic regions. Cretaceous Coast Plutonic Complex and Upper Triassic volcanic and sedimentary rocks of the Whitehorse Trough are separated by the 40 km long 140° trending "Tally-Ho Shear Zone." East of the shear zone, limestone containing late Upper Trassic conodonts is interbedded with volcanics previously mapped as Mesozoic volcanics, and now considered part of the Lewes River Group. Mount Skukum and Bennett Lake are two Eocene volcanic complexes in the map area. The volcanic stratigraphy of the Skukum Complex has been reinterpreted and a number of previously unreported rhyolite porphyry plugs and related flows were mapped in other areas outside the main volcanic complexes. U-Pb age dating of zircon concentrates from three plutons was completed. Megacrystic feldspar granodiorite, dated at 220 ± 5 Ma, intrudes the Lewes River Group volcanics. The granodiorite forms a regionally extensive northwest trending late Triassic batholith and is…

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