OSL surface exposure dating of a lithic quarry in Tibet: Laboratory validation and application

Abstract

A B S T R A C TRecent work has shown that the optically stimulated luminescence (OSL) signal can be used to determine the duration of daylight exposure for rock surfaces, complementing the surface exposure dating technique using cosmogenic nuclides. In this study we investigate the feasibility of using the newly developed OSL Surface exposure dating technique (OSL-Surf) to date flake scars at lithic quarry sites. We performed the first quantitative validation of the model describing the OSL-Surf dating technique using a controlled laboratory experiment. Our results show that longer laboratory bleaching durations yield deeper OSL-depth profiles, validating the use of OSL-Surf approach for relative dating of rock surfaces with different exposure ages. The OSL-surf model fitted to the OSL-depth profiles (excluding one outlier) yields accurate estimates of known exposure duration, thus confirming the method's usefulness as an absolute dating tool. Consequently, we used the OSLSurf technique to determine an exposure duration of 117 ± 37 a for a previously unknown-age flake scar that is related to human exploitation of a lithic quarry site in Tibet. The problem of finding a known-age rock surface for parameter calibration was solved by revisiting the sampling site and collecting the scar remaining after earlier sample collection, which has a precisely known exposure age (1.667 a in this study) and identical lithology and irradiation aspect as the flake scar. The calibration sample yielded a measurable OSL-depth profile that could be used to calibrate the model to estimate the exposure duration of a flake scar associated with human exploitation of the area. Finally, we observe that the μ parameter of the OSL-Surf model varies considerably between the laboratory-bleached and two naturally daylight-bleached datasets, despite having identical lithologies. We thus infer that, in addition to lithological controls, the μ parameter is primarily sensitive to the daylight irradiation geometry and only weakly dependent on spectrum of the incident light; this interpretation implies a narrow effective bleaching wavelength band in quartzite. From the practical viewpoint, our results suggest that geometrical factors deserve a careful consideration both while designing the laboratory bleaching experiments as a surrogate of natural bleaching, as well as while choosing the field calibration samples.

Luminescence dating of buried cobble surfaces from sandy beach ridges: a case study from Denmark

“…Other studies have reported similar observation of bleaching to depths >20 mm (e.g. Sohbati et al 2012;Ou et al 2018;Gliganic et al 2019), although these were usually observed in visibly translucent samples, such as quartzite.…”

“…; Gliganic et al . ), although these were usually observed in visibly translucent samples, such as quartzite.…”

Evaluating post-glacial bedrock erosion and surface exposure duration by coupling in-situ OSL and <sup>10</sup>Be dating

“…They showed that the attenuation coefficients are different according the energy of stimulation (e.g., IRSL measured at 50 °C and the post-IR IRSL signal measured at 225 °C). Meyer et al (2018) and Gliganic et al (2018) have shown that the distribution of opaque minerals between rock slices can significantly affect the reproducibility of luminescence-depth profiles. They conclude the need for close petrographic analysis of luminescence-depth profile samples to ensure that the rock cores from calibration and application sites have a similar 5 mineralogical composition and therefore share similar µ parameter.…”

“…Luminescence dating is based on the accumulation of trapped electrons through time in the crystalline lattice of specific minerals (e.g., quartz or feldspar), which are sensitive to daylight (Aitken, 1985;Huntley et al, 1985). In addition to its 30 common application to date sediment burial in a range of geomorphological environments (e.g., Duller, 2008;Rhodes, 2011;Fuchs and Owen, 2008), luminescence dating can also be used to determine the exposure of both naturally formed and anthropogenically formed rock surfaces (e.g., Polikreti et al, 2003;Sohbati et al, 2011;Gliganic et al, 2018;Lehmann et al, 2018). This latter application is based on the principle that when a rock surface is exposed to daylight, the luminescence signal, Earth Surf.…”

“…For a bedrock OSL profile which is not in equilibrium, measuring and calibrating the depth-dependent luminescence signal beneath the exposed surface by generating luminescence depth profiles enables estimation of an apparent exposure age. OSL 10 surface exposure dating is thus presented as a relatively new surface exposure dating method and has already been applied on both geological and archaeological rock surfaces (Polikreti, 2007;Sohbati et al, 2012a;Freiesleben et al, 2015;Meyer et al, 2018;Gliganic et al, 2018). Sohbati et al (2012c) were able to quantify the exposure age of historical rock art from the Great Gallery rock art panel in the Canyonlands National Park (southeastern Utah, USA).…”