A Revised Estimate of the Age of the Earth

Abstract

SINCE the publication of my preliminary account of a new method of estimating the age of the earth¹, based on Nier's isotopic analyses of samples of lead from galena and other lead minerals of known geological age, I have revised the calculations, using Glaisher's Exponential Tables², and greatly increased the number of solutions. 1,419 solutions for t₀ (the time since the isotopic constitution of the earth's primeval lead began to be modified by additions of lead isotopes generated from uranium I, actinium U and thorium) and for x and y (the respective isotopic abundances of Pb²⁰⁶ and Pb²⁰⁷ in primeval lead) have been obtained from the following combinations of data (Table 1). The numbers are those of the lead samples as listed in the original article¹, and the italicized figures in brackets are the approximate ages in millions of years (t_m) of the parental lead minerals. The data for six samples have not been used : either because the ages of the parent minerals are unknown or because the constitutions of the leads are so abnormal as to give highly discordant and mutually divergent results.