Thermoluminescence Dating of Sediments

Abstract Thermoluminescence (TL) dating of sediments is based on the observation that exposure of quartz and feldspar to sunlight rapidly reduces the TL level to a small residual value. Therefore, sediments transported by air or water will usually be deposited with a very small TL level. When the sediment has been covered as a result of subsequent sedimentation, the TL level again increases with time as a result of exposure of the minerals to the natural background radiation. The TL level is thus a measure of the accumulated radiation dose (the palaeodose), and the time elapsed since sedimentation is given by the ratio of the palaeodose to the annual dose. Techniques for determining the palaeodose are described including the regeneration, additive dose and R-T methods. Insufficient bleaching during transport, instability of the latent TL signal and non-linear dose response for older samples pose particular problems which are discussed. In several respects, TL dating of sediments is still at the experimental stage, but the method has a great potential for dating sediments within the last 500,000 years, a period for which there are few other absolute dating methods.