COMPARISON OF CORRECTIONS FOR ANOMALOUS FADING IN POTASSIUM FELDSPAR: A LUMINESCENCE DATING CASE STUDY

The Cooper’s Ferry archaeological site is important to understanding early lithic technologies in the northwestern United States. The site, located on an alluvial terrace at the confluence of Rock Creek and the Salmon River in Idaho, contains a Western Stemmed Tradition cultural assemblage component with radiocarbon dates that align with the ages of Clovis technology. We used single grain post-infrared, infrared stimulated luminescence (PostIR-IRSL₂₂₅) on potassium feldspar to refine the chronostratigraphy at the site. To evaluate the fading of the feldspar luminescence signal, we compared fading tests on single grains, multigrain 2 mm aliquots, and on single grain discs analyzed with a multigrain approach. The ages calculated using single grain fading corrections are in strong agreement with independent age control and have overall low error (~5%) and low overdispersion (typically < 12%). These results prompted a comparison and evaluation of different methods commonly used to measure luminescence signal fading.