Investigating the use of two-dimensional OSL laser scanning instruments and energy-dispersive x-ray spectroscopy for OSL exposure dating

Abstract

Optically Stimulated Luminescence (OSL) depth profiles can be used to extrapolate rock surface exposure ages by understanding a sample's light attenuation and OSL bleaching behaviors. However, the current measuring procedure for producing depth profiles, by measuring the luminescence of millimeter slices from surface core samples, offers limited resolution data, limiting parameter extrapolative precision. The use of OSL laser scanning measuring protocols on transverse core slices has potential for improving the data resolution of OSL depth profiles from core samples. An 11-year exposed rock surface was parameterized for light attenuation and luminescence bleaching rates using depth profile data from four surface cores collected via wafer and scan measuring techniques, to show the potential of OSL laser scanning to improve depth profile dataset resolutions and parameter extrapolative precision. Additionally, non-quartz OSL anomalies were filtered from scan datasets to determine if non-quartz mineral filtering can further improve the resolution and parameterization of depth profile datasets. OSL scanning measures improved the resolution of depth profiles over wafer derived depth profiles for the measured samples, and in comparing absolute uncertainties of parameters, broadly improved parameter precision using maximum likelihood estimate fitting protocols. Non-test dose corrected spatially resolved data error bounds were generally larger than from wafer derived data. When compared to unfiltered spatially resolved depth profile data, OSL anomaly filtered scanned depth profiles improved error bounds of anomaly affected data, and improved parameter extrapolative precision with roughly a similar effect as using non-filtered scan data. The absolute uncertainty in parameterization was impacted by scatter prevalent from scan datasets, which is caused by low OSL sensitivity from samples, the potential recording of remnant OSL, the lack of regenerative dose normalization applied to the scan dataset, as well as other scanning instrument measuring limitations. Still, these influences can be mitigated with optimized instrumentation and scanning protocols.