Uranium–thorium dating

In 1908, John Joly, a professor of geology at Trinity College Dublin, found higher radium contents in deep sediments than in those of the continental shelf, and suspected that detrital sediments scavenged radium out of seawater.

In the late 1980s, the method was refined by mass spectrometry, with significant contributions from Larry Edwards.

[5][6] After Viktor Viktorovich Cherdyntsev's landmark book about uranium-234 had been translated into English, U-Th dating came to widespread research attention in Western geology.

Uranium–thorium dating has an upper age limit of somewhat over 500,000 years, defined by the half-life of thorium-230, the precision with which one can measure the thorium-230/uranium-234 ratio in a sample, and the accuracy to which one knows the half-lives of thorium-230 and uranium-234.

[citation needed] U-Th dating yields the most accurate results if applied to precipitated calcium carbonate, that is in stalagmites, travertines, and lacustrine limestones.

This graph allows one to determine the age from two activity ratios, assuming that thorium is initially absent. The horizontal axis is while the vertical axis is Each curve is a linear fractional hyperbola . There is no closed-form expression for the age as a function of the ratios.