Uranium series disequilibrium dating

Abstract

Decay series commencing with the parents ²³⁸U and ²³⁵U include radioactive isotopes of numerous elements. These daughters can be separated by geological processes such as chemical weathering, adsorption on suspended clay minerals, mineral precipitation from aqueous solutions through biological and inorganic intervention and, during deep-seated magma formation in the Earth, by lava flow crystallization at its surface. Such processes produce disruption in the series through differences in the geochemical properties of the daughters and create geochronological opportunities; for instance, a member separates from its parent and then decays at a rate determined by its own half-life. These effects are utilized in a number of geochronometers applicable to ages extending from several years to 1 Ma or even more. Thus, the geological history of the Earth during the past million years can be investigated, and this plugs a gap between ¹⁴C and K—Ar as dating mechanisms.