Chronometric dating techniques based Free amature adult chating
Stratigraphic dating is based on the principle of depositional superposition of layers of sediments called strata.This principle presumes that the oldest layer of a stratigraphic sequence will be on the bottom and the most recent, or youngest, will be on the top.The earliest-known hominids in East Africa are often found in very specific stratigraphic contexts that have implications for their relative dating.The majority of chronometric dating methods are radiometric, which means they involve measuring something related to radioactivity, for example radioactive decay.They are called chronometric because they allow one to make a scientific estimate of the date of an object as expressed in years.They do not, however, give "absolute" dates because they merely provide a statistical probability that a given date falls within a certain range of age expressed in years.Chronometric methods include radiocarbon, potassium-argon, fission-track, and thermoluminescence.Relative dating methods allow one to determine if an object is earlier than, later than, or contemporary with some other object.
The most common relative dating method is stratigraphy.
Other methods include fluorine dating, nitrogen dating, association with bones of extinct fauna, association with certain pollen profiles, association with geological features such as beaches, terraces and river meanders, and the establishment of cultural seriations.
Thermoluminescence (TL), optically stimulated luminescence (OSL), and electron spin resonance (ESR) are all trapped charge dating techniques.
These techniques use signals arising from electrons trapped in the crystalline structure of a sample to calculate the time since the traps were empty.
For TL and OSL, the population of trapped charges is measured by the amount of light emitted by electrons released from their traps.
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Electrons are not evicted by ESR spectrometry; the strength of the signal emitted by trapped electrons provides a measure of the population size.