Cross-Calibration and Sensitivity Analysis of OSL Rock Surface Exposure Dating Using Cosmogenic Nuclide Ages on an Uinta Mountains Rock Glacier (Utah, USA)

Rock glaciers are common permafrost features in mountain landscapes around the globe with a geohazard relevance sourcing large amounts of debris while also acting as aquifers storing large amounts of water, yet their long-term (i.e. centennial to millennial scale) dynamics remain poorly constrained due to limited dating efforts. Short term observations, via GPS, InSAR, UAVSAR, Lidar or feature tracking, show acceleration of flow rates of rock glaciers in all mountain regions.

We use rock glacier RG-2 in the Uinta Mountains (Utah, USA, 3 300 m asl) as a natural laboratory to test and cross-calibrate a novel luminescence-based surface dating technique: optically stimulated luminescence rock surface exposure dating (OSL RSeD). This method exploits the latent OSL or IRSL signals stored in quartz and feldspar bearing rocks and the fact that, in the upper centimeters of rock surfaces, these signals are reset (zeroed) by daylight exposure. By integrating previously CRN-dated quartzite boulders (n = 9) on RG-2 into our analysis, we (i) assess the sensitivity of parameters in the OSL bleaching-with-depth model, (ii) evaluate the model’s underlying assumptions, and (iii) interpret the resulting OSL ages.

Furthermore, we present a standardized, statistically robust workflow to normalize luminescence-depth profiles to saturation based on sequential analysis, suitable for datasets obtained by the 1D-coring-and-slicing- as well as the 2D-EMCCD-approach for various geological and archaeological dating applications.