Abstract

This paper is designed to provide a glimpse of the major Cenozoic geologic events that built, shaped, and modified the spectacular upper Yellowstone Valley during Cenozoic time. For clarity and chronologic presentation, the authors have divided the text into three essays which outline the Cenozoic structural, volcanic, and geomorphic-glacial history. R. A. Chadwick was responsible for the volcanic discussion while J. Montagne took the lead in the remaining two subjects.

The essay was originally prepared to accompany Field Trip 1, for the Rocky Mountain Section of the Geological Society of America in May, 1982, and is presented here through the courtesy of the Montana Bureau of Mines and Geology whose pending Publication 86 will formally include the manuscript.

Studies of this area over the past twenty years have been aided by the support of two grants from the National Science Foundation, G-24326, and GP-2912, for which the authors are grateful. In addition, the Montana State University Endowment and Research Foundation contributed financial aid and support. We are also indebted to many graduate students for their aid in the field, among them W. A. Van Voast, J. A. Bush, E. M. Struhsacker, S. E. Personius, and Albert Basler whose theses contributed importantly to this treatise. Visits in the field with John Good, Clifford Montague, K. L. Pierce, J. D. Love, and our late colleague, W. J. McMannis have stimulated progress in a variety of geologic ways. The Bruce Weeter, James and William Warfield, and Nelson families have been particularly helpful in giving access to critical areas. The cooperation of the MSU Earth Sciences Department and its former Head, M. J. Edie are gratefully acknowledged. We are indebted to D. L. Smith for critical reading and editing of the manuscript.