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.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.In the same way, more or less, OSL (optically stimulated luminescence) dating measures the last time an object was exposed to sunlight.
All methods agreed within their respective dating uncertainties confirming the utility of all four methods.
They indicate an age for the emu egg of 31.24 ± 0.34 ka.
But when the rock is exposed to high enough levels of heat or light, that exposure causes vibrations in the mineral lattices and the trapped electrons are freed.
The exposure to radioactive elements continues, and the minerals begin again storing free electrons in their structures.
The sediment infilling the egg provided material for luminescence dating that minimized problems of association.