This is the only type of techniques that can help clarifying the actual age of an object.Absolute dating methods mainly include radiocarbon dating, dendrochronology and thermoluminescence.Indeed, carbon 14 (14C) is formed from the reaction caused by cosmic rays that convert nitrogen into carbon 14 and then carbon dioxide by combining with carbon 12 (12C) and carbon 13 (13C ), which are stable carbon isotopes.Following the death of an organism, any exchange ceases and the carbon 14, which is radioactive and therefore unstable, slowly begins to disintegrate at a known rate (half-life of 5730 years, ie, after this period only half of the total carbon 14 present at the time of death remains).Dendrochronology Dendrochronology is a method that studies the rings of tree trunks to define characteristic sequences by analyzing the morphology of growth rings for a given species.This method is based on the principle that the variation in tree growth from one year to another is influenced by the degree of precipitation, sunshine, temperature, soil type and all ambient conditions and that, consequently, reference patterns can be distinguished.
These methods usually analyze physicochemical transformation phenomena whose rate are known or can be estimated relatively well.
However, this method is sometimes limited because the reoccupation of an area may require excavation to establish the foundation of a building, for instance, that goes through older layers.
In this case, even if the foundation of the building is found in the same stratigraphic level as the previous occupation, the two events are not contemporary.
Subsequently, the calibration of that date provides a time interval where the event or object being dated can be situated (eg, 1275-1425 AD).
Radiocarbon dating, however, can only be used for dating objects that are less than 50 000 years.