Rock varnish dating
The dating method devised and used by ASU's Ronald I.
Cation-ratio dating of rock varnish is an empirical surface-exposure dating method based on decreases in the cation ratio (Ca K): Ti over time.
Although these changes were attributed to the preferential leaching of Ca and K from varnish, the existence of such leaching has not been demonstrated.
In varnish collected from the Cima volcanic field, California, distributions of the minor elements used in cation-ratio (CR) dating reflect varnish stratigraphy as defined by the major elements Mn, Fe, and Si.The article in Science revealed that an analysis by two AMS laboratories found pieces of coal and/or charcoal-like material in about 80 of Dorn's samples from previous projects.