Establishing standardised growth curves (SGCs) for OSL signals from individual grains of quartz: A continental-scale case study

The standardised growth curve (SGC) procedure is a technique that can facilitate rapid D-e estimation. In this study, we apply a least-squares (LS) normalisation procedure to single grains of quartz from multiple sites across Australia to test its applicability for establishing common SGCs for individual quartz grains from the same continent. Seventy-two samples from 18 sites were divided into two groups: (1) forty samples were used to construct common SGCs for Australian quartz, and (2) thirty-two samples were used to blind test the reliability of single-grain dating, based on the continental SGCs. Individual grains of quartz from different sites exhibit significant variability in their OSL decay curves, inherent signal intensities and dose response curves (DRCs) constructed using the single-aliquot regenerative dose (SAR) procedure. Application of a LS-normalisation procedure can largely reduce between-grain variability in the shape of the DRCs, allowing for the establishment of a suite of continental SGCs for Australian quartz. For radiation doses below 50 Gy, all investigated grains share a single, common SGC. At higher doses, the DRCs can be divided into six groups, with each group represented by a common SGC. The proportion of grains belonging to each group shows no discernable dependence on OSL properties, but varies significantly among the different sites. The single-grain D-e values determined using the continental SGCs are consistent at 2 sigma with those obtained from their individual DRCs. Likewise, the single-grain D-e distributions obtained using the SGCs and the individual DRCs are similar for most of the blind-test samples. Discrepancies for a small number of samples can be explained by the inclusion in the SGC D-e dataset of a few outlying values associated with aberrant or saturated grains. Our results show that the establishment of a group of continental SGCs can significantly reduce the machine time required for single-grain OSL measurements, enabling more samples and/or more grains to be measured per unit time. Continental SGCs also yield single-grain D-e estimates with comparable accuracy and precision to those obtained from individual DRCs constructed using the full SAR procedure.