Uranium Series Dating

Uranium decays through a number of radioactive daughter isotopes, some of which have half-lives comparable to the time scale of prehistoric archaeology. The growth of these isotopes in naturally occurring materials at archaeological sites can be used to determine the age of sites. The growth of 230Th from its parent, 234U, can be used over a time range from a few hundred to half a million years. Calcite precipitated from running or dripping water in springs and caves, as well as marls and soil-deposited calcretes may be spatio-temporally associated with archaeological materials; they can be dated by 230Th/234U and 234U/238U measurements with a precision of ±5–10% of the age (by alpha counting) or ±1% (by mass spectrometry). Bones, teeth, mollusk and egg shells, are also datable but present problems due to migration of parent U in and out of the samples during their burial history.