Optically Stimulated Luminescence (OSL)

Luminescence dating is based on the ability of certain minerals (quartz and feldspar) to accumulate electrical charges within their mineral structure and to release such energy when they are exposed to an external stimulus. According to the type of external stimulus applied, there are different types of luminescence, TL, OSL, IRSL, depending on whether the external source is heated, a visible light source or infrared. The energy accumulated within the minerals is a result of the radioactive decay occurring in the material found in the environment, such as U, Th and K present in the sediment. The energy is continually stored until the minerals are exposed to an external stimulus, such as sunlight, for example, resulting in the release of the energy, thereby resetting the clock to zero. Therefore, this technique can only be employed to date the last event when the material was exposed to sunlight, having been subsequently buried and protected from this light source. Optically stimulated luminescence (OSL) is a method for measuring doses from ionizing radiation. It dates directly the minerals (quartz and feldspar) forming the sediment.