Chronometric Dating in Archaeology: A Review

Most archaeological dating methods are based on decay of a naturally occurring radioisotope. (14)C activity of fossil bones and charcoal decreases with age, but must be calibrated for past changes in atmospheric activity. Uranium absorbed by shells and stalagmites is used to date on a 10(5)-year scale by observing the decay of (234)U to (230) Th. Thermoluminescence, optical luminescence, and electron spin resonance detect trapped electronic charges generated by natural radioactivity in burned flint, beach sands, shells, and tooth enamel. Rate of racemization of amino acids in fossil shells is constant at constant T, and age can be tracked from an increase in the D/L ratio.