BAYESIAN ANALYSIS OF PLEISTOCENE CHRONOMETRIC METHODS*

Bayesian analysis of radiocarbon dates on Holocene archaeological sites has become well established. Application to Pleistocene sites dated by multiple techniques would be advantageous. This paper develops the necessary mathematical apparatus in the form of likelihoods for luminescence dating, and uranium‐series dating, and considers the possibility for amino‐acid racemization dating. Application of the new methods is illustrated using the stratigraphic sequences of dates from the sites of Saint‐Césaire and La Chaise‐de‐Vouthon. For application to amino‐acid racemization dating, fuller publication of data is found to be required.     

THE AMINOCHRONOLOGY OF MAN‐INDUCED SHELL MIDDENS IN CAVES IN NORTHERN SPAIN*

Here, we provide the first report on the ages of 54 archaeological levels in 38 caves in northern Spain by means of the aspartic acid d /l ratio measurements in Patella shells, with good results. For this purpose, we developed an age calculation algorithm that allows the numerical dating of deposits from other archaeological localities in the area and nearby regions. We conclude that the sample size—that is, the number of shells analysed within a single level—reinforces the importance of analysing numerous specimens per horizon and the understanding of the time‐averaging concept. The ultrastructure of different species of Patella shells was also studied, showing calcite in their apexes and aragonite at their margins.     

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.     

OPTICAL DATING OF SINGLE AND MULTIPLE GRAINS OF QUARTZ FROM JINMIUM ROCK SHELTER,NORTHERN AUSTRALIA: PART I,EXPERIMENTAL DESIGN AND STATISTICAL MODELS*

Jinmium rock shelter is famous for the claims made by Fullagar et al. (1996) for the early human colonization and ancient rock art of northern Australia. These claims were based on thermo-luminescence ages obtained for the artefact-bearing quartz sediments that form the floor deposit at the site. In this paper, we outline the background to the optical dating programme at Jinmium, and describe the experimental design and statistical methods used to obtain optical ages from single grains of quartz sand. The results, interpretations, and implications of this dating programme are reported in a companion paper (Roberts et al. 7999, this volume).     

A NEW THERMOLUMINESCENCE DATING TECHNIQUE FOR HEATED FLINT*

A new thermoluminescence (TL) technique for determining the age of heated flint artefacts from archaeological sites is presented. It is a variant of the SAR protocol, which is usually used for OSL dating of sediment, but it is not based on a presumed model for fitting the dose–response curve. Dose recovery tests as well as comparisons with standard protocols show the accuracy of the new technique. It is found that the sensitivity of the thermoluminescence (TL) signal of flint in the orange–red waveband does not show severe changes due to the heating process while measuring the TL. This allows the application of a short SAR procedure, which requires only two dose points. The technique does not require as much instrument time as other SAR techniques, and thus is advantageous for dating very old samples. The major advantage of this new technique is the small amount of sample material required, which allows the dating of samples that are too small for standard TL dating techniques.     

LUMINESCENCE DATING OF POTTERY FROM LATER PREHISTORIC BRITAIN*

Dating of later prehistoric settlements relies heavily on potter; typologies in England and yet there has been little scientific dating in order to verify these typologies. In this work, luminescence dating techniques were applied directly to the pottery which forms the typological framework. Excellent agreement was obtained between the luminescence ages, and archaeological age ranges for known‐age pottery sherds with diagnostic form and surface decoration. A lower correlation, however, was found in several regions between the luminescence ages for undecorated body sherds and the archaeological assessment which was necessarily based solely on fabric, suggesting the need for reassessment of these fabric chronologies.     

RADIOCARBON DATES FOR BEESWAX FIGURES IN THE PREHISTORIC ROCK ART OF NORTHERN AUSTRALIA

Accelerator mass spectrometry radiocarbon ages have been taken for a test suite of small samples of material removed from some of the ‘beeswax’art figures found in rock shelters in northern Australia. The results indicate that we can reliably date this unique form of rock art with no noticeable damage. We had not expected to find figures of any great antiquity, and so we were surprised to find that the ages obtained spanned the time period from the recent past to about 4000 BP.     

Rock surface luminescence dating of prehistoric rock art from central Iberia

Rock art paintings are notoriously difficult to date numerically. Recently, luminescence dating has been shown to provide reliable rock surface burial ages in various archaeological settings. Here we use the cross-cutting relationship between a fallen rock and two paintings of the Iberian Levantine (older) and Schematic (younger) styles to constrain the age of the paintings by dating the rockfall event using rock surface luminescence dating. Infrared-stimulated luminescence (IRSL) signals as a function of depth into the buried face of the talus border indicate that the IRSL signal measured at 50°C (IR₅₀) was sufficiently reset to a depth of about 1.6 mm prior to burial. An uncorrected IR₅₀ age of 1.6 ± 0.2 ka was calculated for the rockfall event by dividing the surface equivalent dose (D_e) by the total dose rate. This age was corrected using both conventional and field-to-laboratory saturation approaches to yield indistinguishable ages of 2.7 ± 0.5 and 2.9 ± 0.3 ka, respectively. Since the panel with Schematic art was first available to the artist after the rockfall, we conclude the Schematic rock art at Villar del Humo is younger than ~2.9 ka. The Levantine rock art was painted on a panel constrained by the talus boulder before detachment, and so it is likely to be older than ~2.9 ka.     

ISSUES RELATED TO DETERMINING BURIAL CHRONOLOGY BY FLUORIDE ANALYSIS OF BONE FROM THE MAYA ARCHAEOLOGICAL SITE OF CHAU HIIX,BELIZE*

Fluoride percentage of bone is often used to determine relative dates of burials in archaeological contexts. An analysis of prehistoric Maya burials at Chau Hiix, Belize, identifies taphonomic factors, including soil composition, grave depth, soil disturbance, age at death and cortical bone thickness, that cause variations in the rate of fluoride absorption by altering the access of water to bone. This example demonstrates that fluoride dating is unlikely to be useful at most prehistoric Maya sites because of the inconsistent taphonomy due to typically diverse mortuary practices, and it also serves as a cautionary tale for applications of this methodology in other contexts.     

OPTICAL DATING OF GRANITIC STONE SURFACES*

A novel luminescence methodology for dating surfaces of granitoid rocks is presented, with encouraging results for archaeological stone structures. It is based on the zeroing of the latent signal of optically stimulated luminescence (OSL) in feldspar and quartz grains of the stone surface during exposure to daylight. When after bleaching the surface is shielded from light, the OSL signal builds up again, such that its intensity provides an age for the event of the last exposure to light. This event could be the construction or the destruction of stone structures or, for example, sedimentary deposition of granitic boulders, such as in fan deposits. The experimental approach utilizes a high spatial resolution detection technique (HR‐OSL) for OSL of minerals that are left in their original petrological context; that is, without any mineral separation. With this approach, steep gradients in microdosimetry at the surface and at grain boundaries become important and are discussed in detail. The new dating technique is successfully applied to a stone wall of the medieval castle of Lindenfels in southwestern Germany and the pre‐Columbian Nasca lines (geoglyphs) around Palpa in southern Peru.     

URANIUM‐SERIES AND LUMINESCENCE DATING OF VOLCANIC LITHIC ARTEFACTS*

U‐series dating was used to determine the growth rate of a feldspar‐to‐clay weathering rind in a mid‐Holocene Cascade–Olcott tradition andesite core, and luminescence dating (last exposure to sunlight) was used to date fine‐grained feldspars scraped from the surfaces of similar buried artefacts from a ¹⁴C‐sediment‐dated archaeological site (45KI464) on the wet western slope of the Cascade Mountains of Washington. For U‐series dating, we measured ²²⁶Ra excess (²²⁶Ra excess =²²⁶Ra –²³⁰Th) in five stratigraphic depth controlled rind scrapings. ²³⁸U, ²³²Th and ²³⁰Th were counted by alpha spectrometry, and ²²⁶Ra and ²¹⁰Pb were counted by gamma spectrometry on each sub‐sample.     

SIMS‐SS,A NEW OBSIDIAN HYDRATION DATING METHOD: ANALYSIS AND THEORETICAL PRINCIPLES*

The water diffusion mechanism in obsidian has been revisited with the advent of a new dating approach employing secondary ion mass spectrometry (SIMS). The water diffusion SIMS(+) profile and the concept of a surface saturation (SS) layer in obsidians both provide a sound basis for the new diffusion age equation (SIMS‐SS) and are supported by dated world examples ( Liritzis et al. 2004 ). Here, we present the basic physical–chemical analysis of the mass transport phenomenon on which the new dating method is based. The crucial age parameter of the SIMS‐SS dating approach for archaeological obsidians—that is, the surface saturation (SS) layer—is supported by both theoretical and experimental data.     

DIRECT GAMMA-RAY SPECTROMETRIC DATING OF FOSSIL BONES: PRELIMINARY RESULTS

A non-destructive gamma-ray spectrometry was used for direct dating of fossil animal and human bones taken from an alluvial Quaternary site in northern Italy. The ages were obtained using the U-Pa method: the chronological results are in agreement with palaeofaunal indicators and taphonomic data. The ages of two samples showed concordance with the U-Th method; in a third case good agreement was also found with the radiocarbon date, thus lending credence to our modified gamma spectrometric method.     

THE BRITISH ARCHAEOMAGNETIC CALIBRATION CURVE: AN OBJECTIVE TREATMENT

This paper examines the limitations and deficiencies of the current archaeomagnetic calibration curve in use in Britain and explores a different approach to its construction, drawing on recent advances in this subject, in particular the use of a weighted moving window method of averaging. The main advantage of this method is shown to be its ability to take into account uncertainties in both the magnetic direction and the archaeological date of data used in the calibration curve, leading to a secular variation curve with an associated error estimate. Hence, when dating a magnetic direction, the uncertainties in the calibration curve can be taken into account, as well as the uncertainties in the magnetic direction to be dated.     

A NEW DATING METHOD FOR HIGH‐CALCIUM ARCHAEOLOGICAL GLASSES BASED UPON SURFACE‐WATER DIFFUSION: PRELIMINARY CALIBRATIONS AND PROCEDURES*

The first European settlers came to North America in the early 17th century using glass in the form of containers and decorative objects. Thus, glass is a horizon marker for all historic period settlements and a potential source of chronometric dates at archaeological sites belonging to the historic period in the Americas. We have developed a new absolute dating method based upon water diffusion into the surface of manufactured glasses that predicts diffusion coefficients based upon variation in glass chemical constituents. Low‐temperature (< 190°C) hydration experiments have been performed on a set of five high‐calcium (21.7–28.3%) glasses that were used to manufacture wine bottles from the 17th?19th centuries. Infrared spectroscopy and secondary ion mass spectrometry was used to model the water diffusion/alkali exchange process. The ability of the model to accurately predict archaeological ages was evaluated with artefacts recovered from ceramic‐dated contexts at Thomas Jefferson's plantation known as Monticello.     

THE ROMANESQUE FRIEZE AT LINCOLN CATHEDRAL (ENGLAND)—PRIMARY OR SECONDARY INSERTION? MAGNETIC CONSIDERATIONS*

The current debate about the age of the Romanesque frieze of Lincoln Cathedral weighs archaeological evidence against art history. On the one hand, the panels appear to be an integral part of the original Norman structure built by the first bishop (AD 1072–92). However, on grounds of style and artistic comparisons, art historians argue for a later installation during the restoration of AD 1141–6. In order to determine when the panels were stabilized in the cathedral, we used a new method that measures their degree of remagnetization by the earth's magnetic field since they were quarried. The longer that masonry remains stabilized in a given orientation, the greater its viscous remagnetization. Viscous remanent magnetization dating has previously been successful with this particular type of limestone masonry. Our results lend support to the view that the panels were installed in the early 1140s.     

A NEW METHOD TO DATE PETROGLYPHS

A new calibrated method based on erosion phenomena is presented for the dating of petroglyphs (rock carvings and engravings) and geomorphic surfaces. In contrast to previous methods of petroglyph dating, which sought to determine the age of various mineral and organic deposits coating the art, microerosion analysis attempts to ascertain the time of mark production itself, by creating a geomorphologically based time frame. The method involves the establishment of calibration curves for the crucial variables to be considered. These are the rock type and climate of a particular region, microerosional indices and age. The theory, practical application, and prerequisites of the method are considered, and the paper concludes by defining the disadvantages and advantages of the method.     

K/AR DATING AS A MEANS OF SOURCING LEVANTINE EPIPALAEOLITHIC BASALT IMPLEMENTS

Through K/Ar dating of basalt implements from two Mount Carmel late Epipalaeolithic sites and samples of locally occurring basalts, it was possible to demonstrate clearly that the prehistoric inhabitants of these sites did not utilize the locally available Upper Cretaceous (88–77 My) basalts. The dates of the basalt implements are of Tertiary-Quaternary age (3.7-<0.250 My) which suggests the exploitation of basalt exposures at least 60 km east of the sites. This is the first direct evidence for long-distance exchange/trade of an essential raw material in the Levant as early as 13000 BP.     

High‐resolution geospatial surveying techniques provide new insights into rock‐art landscapes at Shuwaymis,Saudi Arabia

Many parts of the Arabian Peninsula contain rock art that has received minimal archaeological attention or has not yet been thoroughly surveyed. In 2001 an extensive rock‐art complex called Shuwaymis, Ha'il Province, Saudi Arabia was brought to the attention of the Saudi General Commission for Tourism and Antiquities. This paper sets out the results of the first high‐resolution geospatial mapping and recording of rock art at this remote site. The research saw the innovative use of a differential GPS to record rock‐art panels to within 5 mm of accuracy at the site of Shuwaymis‐2, the first time that such technology has been used to record rock art in the Arabian Peninsula. With such technology it was possible to show which of eighty‐three late prehistoric rock‐art panels surveyed were in their original position and which had fallen, and to demonstrate that there was spatial homogeneity of rock‐art styles and composition across the site. The mapping recorded multiple panels of cattle, ibex, equid, large cat and other animals. The depictions of lions and cattle in particular indicate that the rock art must have been engraved no later than the early Holocene humid phase (c.10–6 ka BP).