Thermoluminescence dating laboratory
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The presence of rubidium and cosmic radiation generally play a lesser but contributory roll, and the total radiation dose delivered to the TL phosphor is modified by the presence of water.The period since deposition is therefore measured by determining the total amount of stored TL energy, the palaeodose (P), and the rate at which this energy is acquired, the annual radiation dose (ARD).
Using this technique, it is possible to date many samples from archeological sites, such as ceramics, brick, hearths, fire pits, kiln and smelter walls, heat treated flint or other heat-processed materials, sand and glass.
Radiocarbon dating: radioactive carbon decays to nitrogen with a half-life of 5730 years.
In dead material, the decayed 14C is not replaced and its concentration in the object decreases slowly.
Luminescence dating is particularly appropriate when radiocarbon dating is not possible (either where no suitable material is available or for ages beyond the radiocarbon age limit) or for applications affected by radiocarbon plateau effects (e.g.
post 1700 AD, early Iron Age contexts, late glacial timescales) and when the relationship between the organic materials and the archaeological context is uncertain.
Thermoluminescence (TL) dating of sediments depends upon the acquisition and long term stable storage of TL energy by crystalline minerals contained within a sedimentary unit.
This energy is stored in the form of trapped electrons and quartz sand is the most commonly used mineral employed in the dating process.To obtain a truly absolute chronology, corrections must be made, provided by measurements on samples of know age.The most suitable types of sample for radiocarbon dating are charcoal and well-preserved wood, although leather, cloth, paper, peat, shell and bone can also be used.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.High vacuum TL oven is conceived to heat samples during thermoluminescence analyses.