Characterization, identity, distribution, and source of late Cenozoic tephra beds in the Klondike district of the Yukon, Canada

Abstract

A large number of distal, silicic tephra beds have been preserved in the late Cenozoic deposits of the Klondike region, Yukon Territory. Forty-one tephra samples, representing twelve distinctive beds, are detailed in this study. They range in composition from basaltic andesite to high-silica rhyolite, and were deposited during the late Pliocene to Late Wisconsinan time interval. Seven tephra beds are derived from volcanoes in the Wrangell volcanic field, and four come from the more distant eastern Aleutian arc - Alaska Peninsula region, but the source of the single andesitic tephra is unknown. The widespread and well known Old Crow and Sheep Creek tephra beds have been identified in the Klondike district, but all the other tephra units are characterized in detail for the first time. The ages of most tephra beds are poorly constrained, but will undoubtedly become better known with the application of recently developed glass fission-track methods. Hence, prospects are favourable for the eventual development of a comprehensive and reliable time-stratigraphic framework that will support on-going studies on the late Cenozoic geology, geomorphology, paleontology, and paleoenvironments of the Klondike area.