ENVIRONMENTAL DOSE-RATES AND RADIOACTIVE DISEQUILIBRIUM FROM SOME AUSTRALIAN LUMINESCENCE DATING SITES

Determination of geological/archaeological ages by luminescence dating requires the measurement of the rate of delivery of radiation dose from the sample and its environment. For all age determinations it is necessary to assess whether the dose-rate has been constant during the time that the dose has been accumulating, and to make allowance for it if it was not. We report here results from a number of Australian sites to illustrate the information that can be found about element concentrations, about their distribution and about dose rates. Tests for radioactive disequilibrium form part of these measurements. Such tests take the form of comparison of independent measurements of dose-rates and/or individual elements. In general, there is little or no evidence for disequilibrium in aeolian dune systems, even when the age of the system exceeds 500 ka. However, disequilibrium has been found in several sites subject to wet conditions.