Optically stimulated luminescence dating accuracy
The energy released by stimulating the crystals is expressed in light (luminescence).
The intensity of blue, green or infrared light that is created when an object is stimulated is proportional to the number of electrons stored in the mineral's structure and, in turn, those light units are converted to dose units.
We have to be very careful not to expose the sediments to sunlight when we do this!
Luminescence dating (including thermoluminescence and optically stimulated luminescence) is a type of dating methodology that measures the amount of light emitted from energy stored in certain rock types and derived soils to obtain an absolute date for a specific event that occurred in the past.
The method is a direct dating technique, meaning that the amount of energy emitted is a direct result of the event being measured.
During the 1960s and 70s, the Oxford University Research Laboratory for Archaeology and History of Art led in the development of TL as a method of dating archaeological materials.
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.
Minerals—and, in fact, everything on our planet—are exposed to cosmic radiation: luminescence dating takes advantage of the fact that certain minerals both collect and release energy from that radiation under specific conditions.
Crystalline rock types and soils collect energy from the radioactive decay of cosmic uranium, thorium, and potassium-40.
The number of trapped electrons depends on the total amount of radiation that the mineral has been exposed to.
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.
This energy is lodged in the imperfect lattices of the mineral's crystals.
Heating these crystals (such as when a pottery vessel is fired or when rocks are heated) empties the stored energy, after which time the mineral begins absorbing energy again.
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