THERMOLUMINESCENCE DATING: RADIOACTIVITY IN QUARTZ

Alpha activities measured for four quartz extracts indicate that, in some samples, the alpha dose-rate to the quartz due to radioactivity within the quartz can be significant. Uranium mapping of the quartz by neutroninduced fission tracks shows that the radioactivity is not homogeneously distributed.     

THERMOLUMINESCENCE DATING OF STALAGMITIC CALCITE

The thermoluminescence (TL) method of dating stalagmitic calcite has been applied to twenty-seven samples from two paleolithic cave sites; Pontnewydd, Wales, and Caune de l'Arago, Tautavel, France. Environmental dose-rates were evaluated mainly by means of CaF₂ capsule burials. The ages of the stalagmitic samples were independently determined by means of the uranium series disequilibrium method. In general, good agreement is found between the TL and uranium series dates, which cover a range from approximately 15 000 to 300 000 years B.P. It is estimated that the TL method should extend to the order of a million years in good circumstances.     

DATING ARCHAEOMETALLURGICAL SLAGS USING THERMOLUMINESCENCE*

Thermoluminescence has a great potential for dating archaeometallurgical slags, because the smelting process leads to a well‐defined resetting of the ‘luminescence clock’. However, the complex compositions of slags have unpleasant consequences for TL measurements if the bulk slag substance is used. To overcome this problem, quartz has been separated out of slag matrices by chemical and physical procedures. The TL measurements were carried out on this defined mineral phase. This method was tested with seven slag samples from different locations and ages. In most cases, the TL ages determined show good agreement with reference data.     

AUTO-REGENERATIVE THERMOLUMINESCENCE DATING USING ZIRCON INCLUSIONS

Fired ceramics containing zircon inclusions have been dated by allowing the zircons to regenerate their own thermoluminescence (TL) signal, hence auto-regenerative TL dating. The technique is conceptually straightforward. One first measures the TL accrued since the last heating of the material. The zircon grains are then stored for six months and the TL signal regenerated through self-irradiation is measured. Since the internal dose-rate for zircon is dominated by the internal component the age of the sample is simply given by the ratio of the natural to auto-regenerated signal times the laboratory storage period. The technique, however, requires the measurement of a very small auto-regenerated signal, which introduces a number of experimental and physical complications. The methods for overcoming these problems and successfully dating zircons by auto-regeneration are described.     

THERMOLUMINESCENCE DATING OF A CRUCIBLE FRAGMENT FROM AN EARLY TIN PROCESSING SITE IN TURKEY

Archaeological exploration in the Taurus mountains at Göltepe in south-central Turkey has uncovered a site indicating the presence of extensive tin ore mining and smelling operations The most recent find of smelting crucible fragments allowed for a thermoluminescence-hased age determination spanning a late fifth to early third millennium BC date. This result is consistent with a number of radiocarbon dates derived for charcoal also found at the site. The importance of this site relates to the possible tin production and subsequent trade with southwestern Asia which would have provided this otherwise scarce ingredient to bronze technology in that area. This date is directly for crucible material and thus confirms the antiquity of tin smelting at Göltepe.     

THERMOLUMINESCENCE DATING OF MATERIALS WHICH EXHIBIT ANOMALOUS FADING

This article reports a generalised and systematic approach to the thermoluminescence (TL) dating of samples which suffer from anomalous fading. We hypothesise that the TL signal from each mineral phase is composed of a stable and an unstable portion. The decay of the unstable TL is accelerated thermally, until only stable TL remains. The dating is then carried out on this stable signal. The results, on four known-age, coeval samples, exhibiting gross anomalous fading (25-50% loss over a few days), indicate that many, if not all, samples may successfully be dated with this approach.     

THERMOLUMINESCENCE DATING OF BURNT FLINT AND QUARTZ: COMPARATIVE RESULTS

Thermoluminescence dates obtained from burnt flints and quartz recovered from the same sites are compared. For the Upper Perigordian level at la Vigne Brun (Loire, France), four quartz specimens and three flints yielded average ages of 27 400 ± 2300 and 26 900 ± 2200 years respectively, which are 15% greater than the radiocarbon age obtained for the same site (Evin 1982). For the neolithic site of la Vallée aux Fleurs (Loir et Cher, France), the respective averages of three flints and three ceramic sherds were 6830 ± 560 and 6570 ± 520 years.     

FACTORS AFFECTING THE VIABILITY OF THERMOLUMINESCENCE DATING OF GLASS

The aim of this study is to achieve a better understanding of some of the factors that limit the thermoluminescence (TL) dating of glass. Using a‘model system’(lithium-disilicate samples having different levels of crystallinity from 0 to 100%), we show, first, that the TL of glass is reproducible only if the glass is not heated above its temperature glass transition and second, that there is a clear connection between the TL sensitivity and the degree of crvstallinity of the sample. We conclude that thermoluminescence is not a general dating method for archaeological glass, but it can be applied to particular glass samples that haue specified characteristics.     

THERMOLUMINESCENCE DATING OF POTTERY: AN ASSESSMENT OF THE DOSE-RATE FROM RUBIDIUM

The naturally occurring radioisotope ⁸⁷Rb makes a small contribution to the total dose-rate. Assuming an average potassium:rubidium ratio of 200:1 the contribution is estimated at 2.9% of the B dose-rate From potassium. The effect will be negligible in quartz inclusion dating because of the strong attenuation of the B- emission from ⁸⁷Rb. In fine-grain dating the omission of the ⁸⁷Rb contribution will overestimate the age of a pottery sherd by not more than 2% and this is regarded as of minor importance when the total error in the technique is at least 15%.