Observation of unstable fast component in OSL of quartz

Optically stimulated luminescence (OSL) dating has been applied to quartz grains extracted from a sedimentary layer containing stone tools from the bank of Salawusu River, Mu Us desert in central China. Severe age underestimation was observed by applying the single-aliquot regenerative dose (SAR) dating method when compared with the isochron infrared stimulated luminescence (iIRSL) dating results using potassium-rich feldspar grains of different grain sizes. Preheating plateau and dose recovery tests suggest that the SAR protocol is robust for this sample. Component resolving indicates that the OSL signals were dominated by the fast component. However, the fast component is thermally unstable as shown by pulse-annealing measurements and single-grain study. This leads to OSL age underestimation. To overcome this problem, a method was proposed by combining equivalent dose (De) determination and pulse-annealing experiments using single-grain measurements to select only those grains with the thermally stable signals. For those quartz grains with thermally stable OSL signals, the ages obtained are consistent with iIRSL results.