Middle and Late Paleozoic Stratigraphy, Alaska-Yukon Border Area Between Yukon and Porcupine Rivers

Abstract

ABSTRACT Evidence presented in this paper makes it necessary to question the assignment of a Devonian age to the Nation River Formation, a formation that has long been considered to be of Pennsylvanian and perhaps Early Permian age. If eventually it is established definitely that the Nation River Formation does underlie the Calico Bluff Formation, which is Mississippian in age, then it will be necessary to propose a new formation name for the clastic sequence that directly underlies the Permian Tahkandit Formation throughout the area. The clastic rocks (heretofore assigned to the Nation River Formation) that directly underlie the Permian Tahkandit Formation are shown to thin toward the north and become finer grained. This is interpreted to indicate an island source in the Tanana geanticlinal area on the south.