Based on a discipline of geology called stratigraphy, rock layers are used to decipher the sequence of historical geological events.Relative techniques can determine the sequence of events but not the precise date of an event, making these methods unreliable.Today, many different radioactive elements have been used, but the most famous absolute dating method is radiocarbon dating, which uses the isotope C.This isotope, which can be found in organic materials and can be used only to date organic materials, has been incorrectly used by many to make dating assumptions for non-organic material such as stone buildings.TL Age = Palaeodose (P) _____________ (ARD) TL samples may be collected in open ended or opaque PVC tubes approximately 12cm in length and 6cm in diameter.Whilst it advisable to protect the sample from direct sunlight there is no need to sample at night and the orientation of the specimen is not important.The amount of light produced is a specific and measurable phenomenon.If the specimen’s sensitivity to ionizing radiation is known, as is the annual influx of radiation experienced by the specimen, the released thermoluminescence can be translated into a specific amount of time since the formation of the crystal structure.
The major source of error in establishing dates from thermoluminescence is a consequence of inaccurate measurements of the radiation acting on a specimen.
The presence of rubidium and cosmic radiation generally play a lesser but contributory roll, and the total radiation dose delivered to the TL phosphor is modified by the presence of water.
The period since deposition is therefore measured by determining the total amount of stored TL energy, the palaeodose (P), and the rate at which this energy is acquired, the annual radiation dose (ARD).
The accumulation of trapped electrons, and the gaps left behind in the spaces they vacated, occurs at a measurable rate proportional to the radiation received from a specimen’s immediate environment.
When a specimen is reheated, the trapped energy is released in the form of light (thermoluminescence) as the electrons escape.