OSL specialists overcome these challenges through only sampling certain glacial landforms, where greater sunlight exposure is likely to have occurred prior to deposition e.g. Quartz luminescence dating of Anglian Stage (MIS 12) fluvial sediments: Comparison of SAR age estimates to the terrace chronology of the Middle Thames valley, UK. glacial sandars (or outwash plains) and proglacial deltas are likely to have well bleached sediments. The biggest challenge for OSL dating in glacial environments is partial bleaching (resetting) of the luminescence signal.
We then give our sand sample a range of laboratory radiation doses and measure the luminescence that each dose produces to develop a calibration curve.
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.
We have to be very careful not to expose the sediments to sunlight when we do this!