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.Two forms of luminescence dating are used by archaeologists to date events in the past: thermoluminescence (TL) or thermally stimulated luminescence (TSL), which measures energy emitted after an object has been exposed to temperatures between 400 and 500°C; and optically stimulated luminescence (OSL), which measures energy emitted after an object has been exposed to daylight.To put it simply, certain minerals (quartz, feldspar, and calcite), store energy from the sun at a known rate.Overall, 28 samples extracted from the upper 50 m of core YZ07 were investigated.Preheat plateau and dose recovery tests were conducted.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.
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.
The OSL ages generally increased with depth and indicated a 24-ka sedimentary record for the upper 50 m of the core.
The age–depth relationship revealed two distinct sedimentary periods: (1) very slow sedimentation or even a depositional hiatus from the last glacial maximum (LGM) to the early Holocene (~24 to 8 ka); (2) very fast sedimentation at a rate of ~6 m/ka during the middle to late Holocene (since ~8 ka).
TL dating is a matter of comparing the energy stored in a crystal to what "ought" to be there, thereby coming up with a date-of-last-heated.
In the same way, more or less, OSL (optically stimulated luminescence) dating measures the last time an object was exposed to sunlight.