Uranium/thorium dating of Quaternary carbonates

Gustavsson, J. E. & Högberg, S. A. C.: Uranium/thorium dating of Quaternary carbonates. Boreas, Vol. 1, pp. 247–274. Oslo, 1st December, 1972.
The U/Th methods and particularly the theory of the ²³⁰Th-deficiency method are reviewed. The closed system question is discussed against the background of the growth and structure of the molluscan shells measured. The choice of the half-life value for ²³⁰Th, 75,200 years, is accounted for in a review of the five half-life determinations known to the authors. The measurement procedure starts with the mechanical and ultrasonic cleaning of the sample. Small portions are taken for X-ray analysis. The sample is then divided into two parts. One is treated chemically to separate the uraninium and the thorium, in order to determine the ratio between the activities of the uranium isotopes and to determine the content of ²²⁶Ra. The other part of the sample is used to make the total measurement on the uranium and thorium isotopes simultaneously from the same part of the sample without any chemical pretreatment.