In doing so, they find that basement-involved deformation of the crust around 80—90 Ma caused regional heating of the crust. Accuracy is greater and errors are lower. This led to the discovery of 39Ar, which is derived from 39K Merrihue, The potassium-argon transformation.
Potassium-argon dating, which measures the ratio of potassium to argon, is one radiometric method, but this method of dating is not as precise as argon-argon dating. For a more extensive discussion on the history and development of K-Ar dating see Dalrymple and Lanphere and Glen In going from 40K in equation 1, above to 39Ar, the 9. What happens when the age is too young?