Age to allow dating
This relatively new technique was developed in order to achieve more accurate dates than those obtained from the potassium-argon method.
These include radiometric dating of volcanic layers above or below the fossils or by comparisons to similar rocks and fossils of known ages.
This newer method converts a stable form of potassium (potassium-39) into argon-39.
Measuring the proportions of argon-39 and argon-40 within a sample allows the age of the sample to be determined.
This damage is in the form of tiny marks called fission tracks.
When volcanic rocks and minerals are formed, they do not contain fission tracks.