Potassium-Argon Age of Devils Tower, Wyoming

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Science  27 Oct 1961:
Vol. 134, Issue 3487, pp. 1373
DOI: 10.1126/science.134.3487.1373


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.