Investigating luminescence-depth profiles from rocks with different lithologies

Understanding of the attenuation of light into a rock surface is fundamental to the successful modelling of the luminescence profile in rock resulting from prolonged daylight exposure. Here, we investigate this light attenuation. Variations in apparent attenuation is first examined using the variation of luminescence signals with depth, modelled in two different ways to obtain attenuation coefficients. These results are compared with direct measurement of optical attenuation for three different rock types (sandstone, basalt, and granite). We conclude that global fitting of different exposure times using a constant but unknown μ gives rise to larger errors than free fitting, where we allow μ to be different for each exposure time. Our results show that because of differences in lithology and distribution of luminescent minerals, the direct measurement of optical attenuation overestimates the attenuation based on luminescence signals.