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K (from the surrounding sediment), as well as cosmic rays damage the hydroxyapatite structure of the tooth enamel (fig. From a physical point of view, it can be expressed by the accumulation of unpaired electrons in defects of the crystalline structure (called “traps”) as a function of the absorbed dose of ionizing radiations (alpha, beta, gamma and cosmic) and the exposition time.
In contrast, the dose rate is evaluated by measuring the radioactivity in the tooth itself (in all the dental tissues constituting the tooth, i.e.
enamel, dentine and, sometimes, cement) and in its surrounding (sediment, rocks, etc.).
Consequently, we advise that the tooth should be collected with at least 150 g of its embedding sediment. It can be done either by inserting TL or OSL dosimeters, which will record the gamma dose rate for at least several months, and/or using a portable gamma spectrometer, which can provide rapid dose rate measurements (in 10 to 30 min).
Both kinds of measurements should be done at a 30 cm horizontal depth within the targeted stratigraphical unit, in order to make sure that only the radioactivity of the sediment is recorded.
If this horizontal depth is lower than 30 cm, then the true depth should be reported in order to correct the gamma dose rate results accordingly.
By definition, the cosmic rays are attenuated by the rock and sediment covering the tooth.This may be done using for example high resolution gamma ray spectrometry (HRGS) or inductively coupled plasma-mass spectrometry (ICP-MS).Around 100-150 g of sediment are usually required for HRGS analyses, whereas only a few grams are needed for ICP-MS analyses.However, in the case of sites that are no longer excavated, the sample should be selected preferentially according its proximity to the preserved (available) sections.The alpha contribution from the sediment or the external tissues in contact with the enamel can be easily suppressed in the laboratory by removing at least 20 µm from both sides of the enamel layer.L’enregistrement systématique des données de terrain concernant l’échantillonnage est donc essentiel pour la mise en œuvre de la méthode et l’obtention d’âges fiables.Tags: Adult Dating, affair dating, sex dating