Charles C. Templeton

Determinations of thorium and uranium in sedimentary rocks by two independent methods

Abstract Two independent methods for the determination of uranium and thorium-to-uranium ratios are described. One method is based upon γ-ray spectral analysis; the other is based upon total α-activity and fluorometric uranium determinations. Results and errors of measurements on 4 standard samples and 18 sedimentary rocks of various types are discussed. By applying both methods to the same sample, it is possible to determine if secular radioactive equilibrium exists to within experimental error. Where secular radioactive equilibrium exists in well-homogenized samples, both methods agree to within the experimental errors. The observed thorium-to-uranium ratio in sedimentary rocks ranges from less than 0.02 to more than 20; the two methods presented are capable of measuring this ratio to well within ± l over most of this range.