If we assume that the radiation dose rate of the sediment has remained constant over time, then if we measure that dose rate, we can calculate the sample age. Hollie Wynne (Aberystwyth University) stirs OSL samples being treated with acid in the preparation lab of the Aberystwyth Luminescence Research Laboratory. We make an approximation of the number of trapped electrons by measuring the light that they emit following stimulation by light (hence the name of the technique, “Optically stimulated luminescence”). The OSL signal is reset by exposure to sunlight, so the signal is reset to zero while the sand is being transported (such as in a glacial meltwater stream). Once the sand grain has been buried and it is no longer exposed to sunlight, the OSL signal starts to accumulate. Testing an approach to OSL dating of Late Devensian glaciofluvial sediments of the British Isles. When these quartz or feldspar minerals are exposed to the ionising radiation emitted by the radioactive isotopes in zircons, electrons within the crystals migrate and become trapped in their crystal structure. The number of trapped electrons depends on the total amount of radiation that the mineral has been exposed to. The way that we do this is through sampling sand from the landforms in opaque plastic tubes and taking the sample back to a luminescence laboratory where only red light conditions are used. Optically stimulated luminescence dating of glaciofluvial sediments on the Canterbury Plains, South Island, New Zealand.
Measuring the environmental dose rate for an OSL sample from Glen Tulla, Scotland.
This page was contributed by Dr Georgina King from the Aberystwyth Luminescence Research Laboratory in the Institute for Geography and Earth Sciences. OSL is used on glacial landforms that contain sand, such as sandur or sediments in glacial streams.