Chapter 5 - OSL properties of natural materials

Abstract

This chapter discusses the optically stimulated luminescence (OSL) properties of natural materials of both quartz and feldspars. All natural quartz samples are highlighted to have a strong fast component in the OSL signal, best seen in linear modulation OSL (LM-OSL) measurements. Provided this signal is dominant, sedimentary or heated quartz is dated back to about 100 ka, with the limit related to the saturation of the electron trap. The luminescence sensitivity is altered by thermal treatment and any sensitivity changes that occur during a dating procedure can be monitored. Many advances are also made in the understanding of feldspar infra-red stimulated luminescence (IRSL) behavior. The likely presence of anomalous fading can be detected using the red-IR phosphorescence (tunnelling afterglow) measured at liquid nitrogen temperature (LNT) following room temperature irradiation. A more fundamental limitation of IRSL or OSL dating of feldspars is strongly suggested by the radioluminescence (RL) emission spectra. Thus, the development of correction factors for anomalous fading in samples over 20 ka would still not yield correct ages. For these samples, dating using the IR-RL emission appears to be more appropriate and more reliable.