Prior to the final depositional episode it is necessary that any previously acquired TL is removed by exposure to sunlight.After burial the TL begins to build up again at a rate dependent upon the radiation flux delivered by long-lived isotopes of uranium, thorium and potassium.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 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.
The sample collected should be taken from the centre of a homogenous sphere of 30cm radius.
In the absence of a field gamma spectrometer this is extremely important as the presence of rock or any other dissimilar material within this distance may have an effect upon the radiation dose received by the sample.
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Price, School of Earth & Environmental Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW, 2522.
Phone: (02) 4221 3632, Fax: (02) 4221 4250 Email: [email protected] 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.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.