Optically stimulated luminescence cross-dating from quartz of different grain size

Optically stimulated luminescence (OSL) signals from quartz can be used to determine when a sample was last exposed to sunlight. The total specific energy (dose) absorbed since the last resetting is measured using OSL, and divided by the rate of storage (dose rate) to give the time elapsed from the last heating or daylight exposure. The general equation used to determine the age in luminescence dating is given by the ratio between the Equivalent Dose (ED) and the Annual Dose rate (AD). The ED, measured using luminescence signals, is the total absorbed dose starting from the last "zero event" while the AD, evaluated by in situ and extra situ radioactivity measurements, represents the rate at which energy is absorbed from natural radioactivity present in the sample and in the environment. Evaluation of the environmental dose rate component becomes a crucial point in dating since particular conditions of the site (heterogeneity, lack of structure...) could make age measurement inaccurate. In this work, the conditions for applicability of subtraction dating are tested on a sediment of known age; it allows an age determination that is independent of knowledge of the environmental dose-rate.