This tabulation of ages has been made as a convenience to anyone desiring a quick reference to ages published in the United States from 1956 through 1964. This tabulation does not include all published K-Ar, Rb-Sr, or Pb-a ages, but is probably 98 percent complete. Many of the radiometric ages published in abstracts, footnotes, or personal communications are not included as sample localities are lacking or are not sufficiently detailed to be of value. Such ages are often published in a subsequent article with detailed sample locations and geologic interpretation. There may be some duplication of ages in this tabulation. The references listed are either the original source for an age or the best source in regard to sample location, decay constants, interpretation, etc. For a tabulation of Pb-a ages published prior to 1957, see U. S. Geological Survey Bulletin 1097-B, Lead-alpha age determinations of accessory minerals of igneous rocks (1953-1957) by H. W. Jaffe, David Gottfried, C. L. Waring, and H. W. Worthing (1959). A minor number of unpublished radiometric ages from Ph.D. or M.S. theses are also listed in this tabulation.
The tabulated ages are systematized according to year and state. All ages published during a specific year (i.e. 1956) are grouped together, with the ages listed under the name of the state in which the sample was collected. The states are alphabetized. The dated sample is described as to rock type, location, material analyzed, age(s) determined, radiometric method used, and published reference (by first author only). The complete reference is listed at the end of the tabulation for each specific year. To answer questions about geologic interpretation, decay constants, or location, one must review the source reference.
