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Principles of thermoluminescence dating Free naughty chat no email required

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Thermoluminescence is particularly useful to archaeologists as it provides a means of dating non-organic material such as ceramics and that it can be applied before 50,000 years ago (although not to pottery as there isn't any), beyond the effective range of radiocarbon dating.It has been extensivly applied to burnt flint and in many cases has an advantage over other dating methods as the zero event (heating) is often a direct result of use of manufacture.While it is less precise than radiocarbon dating it has the advantage that it can directly date inorganic materials such as pottery (the most abundant inorganic material on many archaeological sites) through the feldspar and quartz content which have been subject to heating. Beyond artefacts, the method can also be applied to to calcium carbonate deposits, volcanic material and wind and water borne sediment.The method is effective back to about half a million years and although generally less precise than radiocarbon dating thermoluminescence is comparable in precision for the last 1000 years, and more precise over the last 300 where the effects of fossil fuel and neuclear testing have made radiocarbon ineffective.It is useful to geologists and archaeologists who want to know when such an event occurred.It uses various methods to stimulate and measure luminescence.Once evicted from the ‘traps’ the electrons are attracted are attracted back to the ‘holes’ created by ionisation and, on recombination at these centres emit energy in the form of photons.

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The dating of sediments using the luminescence signal generated by optical stimulation (OSL) offers an independent dating tool, and is used most often on the commonly occurring minerals of quartz and feldspar and, as such, has proved particularly useful in situations devoid of the organic component used in radiocarbon dating.The ‘depth’ of the traps within which the electrons are held effectively dictates the point at which a sample will become saturated with charge and so the limit of the dating range.Quartz has been used for dating to at least 200 ka, while the deeper traps of feldspar have produced dates as old as 1 ma.All sediments and soils contain trace amounts of radioactive isotopes of elements such as potassium, uranium, thorium, and rubidium.These slowly decay over time and the ionizing radiation they produce is absorbed by mineral grains in the sediments such as quartz and potassium feldspar.Stimulating these mineral grains using either light (blue or green for OSL; infrared for IRSL) or heat (for TL) causes a luminescence signal to be emitted as the stored unstable electron energy is released, the intensity of which varies depending on the amount of radiation absorbed during burial and specific properties of the mineral.