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.     

THERMOLUMINESCENT DATING OF EGYPTIAN PREDYNASTIC POTTERY FROM HEMAMIEH AND QURNA-TARIF

Eight sherds from Hemamieh and two from Qurna-Tarif, both Predynastic settlement sites in the Nile valley, have been dated by the thermoluminescence method (quartz inclusion technique). The results put the Badarian phase at Hemamieh in the sixth and fifth millenium b.c. , and the Gerzean phase in the first half of the fourth millenium b.c. The dates for the village of Qurna-Tarif fall around 4000 b.c.     

THERMOLUMINESCENT DATING OF FIRED ROCK-CRYSTAL FROM BELLAN BANDI PALASSA,CEYLON

Fired rock-crystal was found within the matrix of a Balangodese (pre-Vedda) burial in a Mesolithic midden in Ceylon; thermoluminescent measurements indicated a date of about 7000 years before present.     

RADIOCARBON DATING BY THERMOLUMINESCENT DOSIMETRY

Work is presented that tests the possibility of performing radiocarbon dating measurements by using the thermoluminescence induced in sensitive phosphors, using existing thermoluminescence equipment. It is concluded that, for such a technique to be viable, a more specifically designed, and more elaborate, system will be necessary. Some comparative results on certain TLD phosphors are also given.     

THERMOLUMINESCENT DATING OF NEOLITHIC AND CHALCOLITHIC POTTERY FROM SITES IN CENTRAL PORTUGAL

Samples of Neolithic and Chalcolithic pottery from nine sites in the Upper Alentejo and Estremadura regions of Portugal have been dated by the thermoluminescence method (quartz inclusion technique). The project was designed to help establish an absolute chronology for the Neolithic and Chalcolithic periods in this area, and to try to elucidate the chronological relationships between settlement sites and burial sites (‘dolmens’) in the same area. Portugal was confirmed, together with Brittany, as being one of the earliest foci of megalith builders.     

THE SUBTRACTION TECHNIQUE OF THERMOLUMINESCENT DATING

Combination of the routine approaches of thermoluminescence dating, the fine-grain and inclusion methods, allows an age to be determined that is independent of knowledge of the environmental dose-rate. This socalled subtraction technique is exampled by several terracottas of museum origin and some pottery collected from archaeological contexts without associated burial media. Age determination is estimated to have an accuracy of around ± 12%, in favourable conditions.     

THERMOLUMINESCENT DATING: ASSESSMENT OF ALPHA PARTICLE CONTRIBUTION

A new system for specifying alpha source strength, in terms of track length per unit volume of sample, is proposed. It is based on the experimental observation that the TL induced per unit length of track is essentially independent of alpha particle energy. The new system avoids the need to make assumptions about sampple stopping power and it is shown to be consonant with the old system as long as up-to-date evaluation of alpha ranges is used. A revised table of dose-rate data is given.     

THERMOLUMINESCENT AUTHENTICITY STUDY AND DATING OF RENAISSANCE TERRACOTTAS

A comparative study is made of the thermoluminescence (TL) of terracottas of the Renaissance era and some known limitations of such ware dating to the middle of the last century. The data shows that conclusions on authenticity of an unknown work can be reliably obtained using this scientific method. Also examples are presented of accurate dating of genuine terracottas despite a lack of knowledge about the environmental circumstances of each piece's archaeological past.     

ALPHA-RECOIL TRACKS IN ARCHAEOLOGICAL CERAMIC DATING

Among the manifestations of radioactive decay which can be etched to optical visibility on the surface of mica are tracks from nuclei recoiling from alpha emission, called ‘alpha-recoil tracks’. If, beforeetching, the mica is heated to temperatures of the order of 600°C, all evidence of these tracks is annealed from muscovite mica in a few minutes. Alpha activity observed on mica from pot sherds, from stones surrounding fire places, from fire pits, and fired daub may constitute an alpha-recoil track clock which started at the moment of the last firing of the artifacts.     

THE ASSESSMENT OF ERROR LIMITS IN THERMOLUMINESCENT DATING

This paper discusses known sources of error, both random and systematic; suggests quantitative limits; and proposes a consistent method for compounding them to yield an overall error in age, both for individual sherds and for the weighted average of a number of sherds from the same context. It is proposed that two error limits should be quoted for the date of a context: first, the standard error of the mean value as calculated from the experimentally observed root-mean-square deviation of the individual samples, and secondly, the expected overall error from the sources discussed in the paper. The former can be considered as a lower limit and relevant when comparing contexts on the same or similar sites whereas the latter is more realistic when comparing TL dates with radiocarbon or archaeologic chronology.     

OPTICAL DATING RESULTS FOR BRITISH ARCHAEOLOGICAL SEDIMENTS

In this paper optical dating results for a range of British archaeological sediments are presented to illustrate the potential this method offers for archaeologists. The optical dating is shown to offer an absolute method for directly dating the deposition of sediments for an age range of approximately 1–300ka. Problems have been found with recuperation of the optically stimulated luminescence signal and insufficient bleaching at deposition of the sediment. A suitable correction method for the recuperation has been found and a method of identifying insufficient bleaching is suggested.