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Rock surface luminescence dating is being increasingly applied to constrain the chronologies of geological and archaeological deposits. Here we investigate the potential of the newly developed Risø Imager, a mobile system for measurements in the field, for screening samples with desirable luminescence characteristics. We show by analysing 8 different rock samples, that the Imagers sensitivity is about 50 times lower that than the more commonly used Risø TL-OSL Reader. However, the measurement sensitivity can be improved using longer acquisition times for non-destructive infrared photoluminescence. The imager provides a far superior resolution and precision in the luminescence-depth profiles compared to the Reader, with measurement times as small as few minutes. However, based on the examination of luminescence values at zero depth, we speculate that cross-talk from the poorly-bleached, regions below the focal plane of the Imager may be a source of contamination in the luminescence depth profiles, an aspect which requires future investigations. • Sensitivity comparison of the Risø TL-OSL Reader and a portable Risø Imager. • Difference between the two systems similar across 8 different rock types. • A clear advantage of the Imager is its unprecedented spatial resolution (<100 μm). • Surface bleaching better in the Reader due to potential cross talk in Imager. • Trivial to obtain luminescence-depth profiles from the Imager in a few minutes. [ABSTRACT FROM AUTHOR]

· A new absolute dating method to determine fracture exposure ages in rocks. · The method is based on luminescence bleaching across fractures by daylight. · Fracture dating is applicable to quartz and/or feldspar bearing rocks. · Potential new insights into factors governing long-term fracture evolution. Rock fracturing (cracking) is a universal process that drives and limits chemical degradation, sediment production and erosion, and deterioration of infrastructure. Despite extensive research gains in rock mechanics on one hand and geochronology on the other, there remains a glaring gap in our ability to understand the long term evolution of natural, in situ fractures. Here we develop a novel fracture exposure dating technique, grounded in modern advances in luminescence geochronology. We apply our new dating method to a granitic boulder from a glacial outwash terrace in California, US. We conclude that the longest, clast-splitting E-W fracture appeared shortly after the boulder's deposit, whereas the secondary N-S fracture appeared 5 ka after the deposition, approximately correlating with the Last Glacial Maximum and Younger Dryas periods of the region, respectively. However, dating of the third fracture (<< 50 µm width) which does not fully split the rock, is ambiguous due to negligible daylight penetration and poor determination of fracture width. The fracture dating method presented herein brings with it the potential to decipher relationships that are crucial for the interpretation and modeling of, for example, long-term landscape and atmospheric evolution relating rock weathering to climate change and erosion. [ABSTRACT FROM AUTHOR]