Evaluation of SAR procedures for D-e determination using single aliquots of quartz from two archaeological sites in South Africa

Abstract

In previous work the conventional Single aliquot regenerative protocol procedure has been demonstrated to work well for a large number of samples. Application of the conventional SAR procedure (but with a range of pre-heat temperatures) to naturally irradiated quartz grains from two different archaeological sites in South Africa showed substantial changes in sensitivity through the measurement cycles; one sample (SIB2) showed no trend in D-e as a function of pre-heat temperature, showing that the sensitivity correction was appropriate, whereas for the other sample (ZB4) there was a trend that could be related to the growth curve construction, rather than measurement of the natural signal. However, application of a conventional SAR procedure, with a 260 degrees C preheat for 10s and a cut heat at 160 degrees C, to quartz grains that had been bleached and given a laboratory dose, resulted in underestimation of the dose by grater of equal to 10%. The effect of raising the cut heat temperature from 160 degrees C was investigated using LM-OSL measurements in order to identify OSL components that are present in addition to the fast component for which SAR was developed. The effects of changing the cut heat temperature and adding a high-temperature optical stimulation between cycles in the SAR procedure were measured for dose recovery tests. The effects of these changes on measurement of D-e values for single aliquots of these two samples are reported. Both modifications improved D-e recovery, and the study emphasizes the importance of carrying out dose recovery tests.