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Abstract

Dating the last exposure of stone surfaces to light could provide valuable information to archaeology and geosciences. However, no known chronometric method is able to elucidate this information to date. In general, OSL is the method used to date problems associated with light and minerals. Yet, gradients of relevant parameters essential to OSL dating exist in all natural samples. Common techniques to control these gradients are not feasible for stone surfaces. This work presents a new approach which includes preparation of samples, highly resolved (up to 25 m) detection of optically stimulated luminescence by imaging to a CCD chip, and a software solution for data analyses. In this way, the area of measurement can be reduced to a size where the gradients become insignificant. Using this method, spatially resolved dating was successfully performed on stone surfaces from the medieval castle of Lindenfels (Odenwald, 12th century AD), Germany, and from the geoglyphs of Palpa, Peru (200 BC 600 AD). Furthermore, the suitability of the approach for new kinds of research on OSL and the applicability for dating pottery samples is shown. However, imaging does not provide direct discrimination between OSL signals at varying depths. To overcome this restriction, a confocal scanning microscope was built with the capability for high resolution recording of optically stimulated luminescence from a defined volume with added spectral information.