Optical Dating of Quartz from Young Deposits

From Single-Aliquot to Single-Grain


Ballarini, M.

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Delft University Press


Optically Stimulated Luminescence (OSL) dating is a tool used in Quaternary Geology
for assessing ages of depositional mineral grains such as quartz, feldspars and zircons. In
particular, OSL showed to be exceptionally robust and reliable for dating quartz samples.
OSL dating relies on the assumption that the luminescence signal of grains is fully reset to zero by sunlight exposure before deposition. If this requirement is not fulfilled (i.e. grains were 'poorly-bleached'), ages may be grossly overestimated. In particular, poor-bleaching can significantly affect age estimations of young sediments. Standard procedures for estimating the burial dose of a sediment make use of a large number of grains (aliquot) that is measured simultaneously. This approach has been shown to work well, but only on homogeneously bleached sediments. An alternative way to investigate poor-bleaching within a sample is to measure the OSL signal from individual grains rather than from aliquots made up of several thousands of grains. The advantage is that individual grains with large doses (possibly due to poor-bleaching) can be identified and dealt with. Drawbacks are that only a small percentage of the measured grains produce detectable signals and luminescence responses are weak. The aim of this publication it to determine the feasibility of applying dating techniques to individual grains of quartz from deposits formed within the last 300 years.