Thermoluminescence dating using fine grains from pottery dating site with paypal
In the case of an older sample this correction may only represent a small proportion of the total age.The radiation dose received annually by the sample is measured by means of calibrated thick source alpha counting which determines the specific activity of the uranium and thorium decay chains assuming that secular equilibrium exists.The technique is best suited to the age determination of sediments which have undergone long transport distances and, in the case of water borne sediments, as suspended load under shallow water, low energy conditions.Aeolian sediments are more likely to have undergone considerable solar exposure prior to deposition and therefore are more likely to have been effectively zeroed.
Whilst it advisable to protect the sample from direct sunlight there is no need to sample at night and the orientation of the specimen is not important.The surface residual TL correction is determined from the modern analogue sample by means of a similar procedure and this correction is applied to the palaeodose value.In the absence of a suitable modern sample the laboratory induced unbleachable TL level is assumed which has the effect of maximising the resultant TL age determined.The sample is taken by introducing the tube into a freshly cleaned back surface; if this proves difficult a block may be cut from the unit of interest.The specimen tube or block should then be wrapped in black plastic to prevent further exposure to light and to preserve the environmental moisture content.
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The exposed material at either end of the tube is used in the determination of the annual radiation dose and the internal unexposed portion for the palaeodose determination.