Three whole-rock K–Ar analyses on andesites from the Indian River area, west central Yukon, yielded dates of 69.0 ± 1.7, 65.2 ± 1.7, and 64.8 ± 1.7 Ma. These confirm earlier dates indicating the Carmacks Group is Late Cretaceous in age. A single date of 51.4 ± 3.9 Ma was obtained from a tuff in the Sixty Mile River area, west central Yukon, suggesting an Eocene age for these deposits. However, this date is considered equivocal because it is anomalous when compared with the other dates from the area.

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