Fission track dating method
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.
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.
Minerals, in fact, everything in 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.
The term luminescence refers to the energy emitted as light from minerals such as quartz and feldspar after they've been exposed to an ionizing radiation of some sort.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.Electrons from these substances get trapped in the mineral's crystalline structure, and continuing exposure of the rocks to these elements over time leads to predictable increases in the number of electrons caught in the matrices.
Better still, unlike radiocarbon dating, the effect luminescence dating measures increases with time.
As a result, there is no upper date limit set by the sensitivity of the method itself, although other factors may limit the method's feasibility.