Assessing Optically Stimulated Luminescence (OSL) signal contamination within small aliquots and single grain measurements utilizing the composition test

Quartz in tectonically active regions can suffer from signal contamination when utilized for Optically Stimulated Luminescence (OSL) dating. Typically, these environments bring quartz-bearing bedrock to the surface, which erodes and enters geomorphic systems with little fluvial reworking, resulting in dim OSL signal response. Conversely, feldspars often have an inherently brighter signal, even among bedrock or freshly eroded samples. Environments with dim quartz can be difficult to date as the signal contribution from errant feldspars may dominate the measured signal. Further, immature sediments may retain mineral inclusions within quartz grains that would have been physically or chemically eroded in more mature sediments. Previously, we presented a signal composition test which utilizes thermal quenching and IR bleaching susceptibility to assess the purity of a quartz sample. Additional measurements have been made, looking at the systematics of how small volumes of feldspar can affect the results of aliquots analyzed with this composition test. Further, different feldspar samples have been assessed for their response to the composition test and chemical compositions were determined using energy-dispersive X-ray (EDX) spectroscopy with a scanning electron microscope (SEM). Finally, we present a single grain protocol for the composition test.