Paper II: The interpretation of measurement-time-dependent single-aliquot equivalent-dose estimates using predictions from a simple empirical model

Narrow spectrum (blue-green) laboratory partial bleaching of aliquots of natural sedimentary quartz has been shown to have a significant effect on equivalent dose (measured using a single aliquot procedure) calculated as a function of measurement time <f>(De(t))</f>. A simple model, based on empirical data, is presented in which the effects of partial bleaching on <f>De(t)</f> are predicted, taking into account the influences of pre- and post-burial doses. The model is applied to the case of heterogeneous populations of partially bleached single grains with various ranges of residual doses. Modelling shows that under realistic conditions, <f>De</f> histogram plots are unable to distinguish between samples having age overestimates and those with correct ages, whereas the proposed <f>De</f>–<f>Z</f> plot is able to make this distinction. Furthermore, modelling shows that <f>De</f>–<f>Z</f> plots can identify sub-populations of grains/aliquots that show most evidence of full bleaching, which can then be used to estimate a correct mean <f>De</f> value. [Copyright &y& Elsevier]