Beta-gradient isochron dating of thin tooth enamel layers using ESR

The theoretical and experimental basis for the development of a new dating technique using beta-gradient isochrons and ESR is presented. For uranium-f ree portions of enamel adjacent to sediment, we can determine a beta-dose g radient due to sources in the nearest 2 mm layer of the sediment. If the eq uivalent dose to successive layers of enamel is plotted against the beta do se rate to each layer, an estimate of the age (equal to the slope of the li ne) that depends only on the environmental beta dose rate can be determined . Experimental methods and results for four teeth are discussed. The signif icance of this approach lies in its ability to isolate an age estimate that is independent of the uranium uptake model, since only portions of the ena mel which are far away enough from internal sources of uranium, such, as de ntine, are used. In addition, this technique provides a time-averaged estim ate of the actual gamma plus cosmic dose rate provided that a reasonable es timate of the average moisture content is used to calculate the environment al beta dose rate. (C) 2000 Published by Elsevier Science Ltd.