Thermoluminescence dating of ceramics three some dating
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.
TL Age = Palaeodose (P) _____________ (ARD) TL samples may be collected in open ended or opaque PVC tubes approximately 12cm in length and 6cm in diameter.
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.
Thermoluminescence dating (TL) is the determination, by means of measuring the accumulated radiation dose, of the time elapsed since material containing crystalline minerals was either heated (lava, ceramics) or exposed to sunlight (sediments).
As a crystalline material is heated during measurements, the process of thermoluminescence starts.
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.
If the specimen’s sensitivity to ionizing radiation is known, as is the annual influx of radiation experienced by the specimen, the released thermoluminescence can be translated into a specific amount of time since the formation of the crystal structure.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). Warning about fakes using ancient materials What about airport x-rays and radiography? Thus, when one measures dose in pottery, it is the dose accumulated since it was fired, unless there was a subsequent reheating. When pottery is fired, it loses all its previously acquired TL, and on cooling the TL begins again to build up.