Geomorphic and Structural Relations of Tertiary Volcanics in the Northern Teton Range and Jackson Hole, Wyoming

The relations of Yellowstone Tertiary volcanics to Tertiary faults in the Teton Range indicate that major movements probably occurred in early Pliocene time, following deposition of Miocene basic volcanics and associated sediments and prior to outpourings of plateau rhyolite, and that minor movements continued into Recent time. Erosion surfaces representing the late-mature stage Black Rock cycle are covered by the rhyolite. This relationship and the youthful geomorphic aspect of the rhyolite plateau indicate that the rhyolite and younger valley basalt are probably of early, or early middle, Pleistocene age. More precise dating of the rhyolite depends upon the age assigned to the Buffalo drift, which rests on these volcanics.