Paper I—simulation of dose absorption in quartz over geological timescales and its implications for the precision and accuracy of optical dating

A theoretical model of quartz luminescence is presented and used to simulate luminescence response to environmental dose rates over geological timescales. Simulations of natural burial and laboratory measurements suggest that dose-rate effects in quartz cause systematic overestimation of absorbed doses when standard dating procedures are applied. Overestimation of absorbed dose (and therefore of age estimates) becomes significant at palaeodoses greater than <f>∼40 Gy</f>. This effect is due to competition from the relatively thermally unstable <f>R1</f> recombination centre (the centre that also plays a key role in ‘dose quenching’ of quartz optically stimulated luminescence, and thermoluminescence). Variation in the concentration of <f>R1</f> centres leads to variation in measured equivalent dose (<f>De</f>) values and may potentially be a significant source of scatter in <f>De</f> estimates from sedimentary quartz samples. Model predictions indicate that by administering laboratory doses either at raised temperature, or in short pulses with intervening thermal treatments, the malign effects of the <f>R1</f> centre can be removed. Results from laboratory measurements using pulsed-irradiation support the theoretical predictions. Implementation of pulsed irradiation in a single-aliquot regenerative-dose procedure yielded an accurate and more precise age estimate for a last-interglacial age dune deposit from Africa, compared to the overestimate obtained using the standard procedure, as predicted by the model. [Copyright &y& Elsevier]