A new Rb–Sr whole-rock isochron for the Skukum rhyolite is 53.3 ± 1.1 Ma with an initial ratio of 0.7053. The rhyolite forms small plugs spatially and probably genetically related to the Skukum volcanic complex in the southwestern Yukon. They were intruded into granitic rocks of the Coast Plutonic Belt. The intrusions are coeval and part of an Eocene plutonic, subvolcanic, and volcanic suite correlated with the Bennett Lake cauldron complex. The initial 87Sr/86Sr ratio matches interpretations of the tectonic evolution of Yukon Crystalline Terrane and Coast Plutonic Complex.