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Quaternary Geochronology 1 (2006) 313-319
Residual thermoluminescence for sun-bleached quartz: dependence on pre-exposure radiation dose.
D. Miallier1, S. Sanzelle1, Thierry Pilleyre1, C. Bassinet1, 2
(2006)

Quartz grains zeroed by heat and subsequently irradiated - either in the laboratory, or naturally in volcanic deposits - were exposed to sunlight for several months prior to TL measurements. As a result, the residual TL, either Blue or Red, appeared to grow significantly with the radiation-dose experienced by the grains since zeroing. In another experiment, un-heated sedimentary quartz grains, sampled at the very surface of a coastal sand-dune, were irradiated and subsequently exposed to sunlight before TL measurements. The residual Red-TL still exhibited a strong dose-dependence, but at a level which was higher than the natural signal. Finally, it was concluded that the so-called “un-bleachable TL” is not a constant, intrinsic data, for a given quartz sample. Because the residual TL is strongly correlated to the radiation dose experienced since the last zeroing by heat, it can theoretically be quoted in terms of “dose”, as sometimes done. However, this raises the question of its correct evaluation, and, on the other hand, there is a risk of misinterpretation of its physical meaning in the case of un-heated sediments. In the context of sediment dating, the experimentally-estimated residual signal that is routinely subtracted from the total signal for palaeodose estimation is therefore higher than the signal that would have been measured prior to burial. Such effect induces an error which can be significant for Red TL. It can be corrected for, at least roughly, from experimental exploration of the dose-dependence of the residual TL
1 :  LPC-CLERMONT - Laboratoire de Physique Corpusculaire de Clermont-Ferrand
2 :  LSCE - UMR 8212 - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
Physique/Physique/Géophysique
quartz – thermoluminescence – sun-bleaching – residual TL
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