Sample geometry and U uptake in archaeological teeth: implications for U-series and ESR dating

Post-deposition U uptake by bones and teeth is the most significant source of inaccuracy in both U-series and ESR dating. In most case's assumptions a bout the form of U uptake are required to calculate a date. We have been us ing the diffusion-adsorption (D-A) model of U uptake to predict the rate of uptake and spatial distribution of U and U-series isotopes in bones, and c alculate open-system ages. Here we develop a similar model to predict U upt ake in enamel and enamel-dentine systems. We find that the traditional mode ls of U uptake, namely linear and early uptake providing maximum and minimu m ages, are not universally applicable. Geochemical changes in the burial e nvironment can lead to leaching or recent accumulation of U. In addition, t he geometry of the tooth affects the pattern of U accumulation, with some a reas of the enamel showing uptake between early and linear, while other are as of the same tooth may exhibit sublinear (recent) uptake. We show, howeve r, how the measurement of the U and U-series isotope distributions (profile s) for a tooth can be combined to model uptake, and provide more reliable U -series dates or ESR dosimetry. (C) 2000 Elsevier Science Ltd. All rights r eserved.