title: Potassium-Argon Age of Devils Tower, Wyoming.
abstract: Devils Tower consists of columnar phonolite porphyry which contains large phenocrysts of orthoclase. Potassiumargon determinations on the orthoclase indicate an age of 40.5 million years +/- 4 percent. This is consistent with the geologically accepted Tertiary age.
authors.forename: W A
authors.initials: WA
authors.lastname: Bassett