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.     

URANIUM-SERIES DATING OF FOSSIL BONES FROM ALPINE CAVES

During the course of an investigation of fossil cave bear populations the uranium-series method for absolute age determination has been applied to bone material. The applicability of the method to bone samples from alpine caves could be demonstrated by the concordance of U/Th and U/Pa ages and cross-checks with the radiocarbon method. Stratigraphic agreement between bone ages and carbonate speleothetn ages also indicates the potential of the uranium-series method as a suitable tool for the age determination of fossil bones from alpine cave environments.     

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.     

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.     

LASER ARGON DATING AND GEOLOGICAL PROVENANCING OF A STONE AXE FROM THE STONEHENGE ENVIRONS*

The recently-developed laser microprobe ⁴⁰argon-³⁹ argon technique has been used to give a geological date for a rhyolitic tuff stone axe fragment from the Stonehenge environs. The method requires only milligramme-sized samples and gives dates of sufficient accuracy to aid in provenancing artefacts to sources, as well as information on the heating history of samples. The axe sample is of Lower Carboniferous date (341 ± 5 Ma) and this limits possible sources to outcrops within the Scottish Midland Valley and small altered exposures in Dartmoor. X-ray fluorescence analysis of the axe suggests the Scottish Midland Valley as the more likely source. The laser argon analysis also shows that the implement had not been heated in antiquity. Laser argon-argon dating can, therefore, be a useful tool in artefact study.     

CONSTRUCTING CARIBBEAN CHRONOLOGIES: COMPARATIVE RADIOCARBON DATING OF SHELL AND WOOD ARTEFACTS FROM PRE‐COLUMBIAN SITES IN CUBA

The lack of robust chronological frameworks for pre‐Columbian archaeology in the Caribbean limits the interpretive potential of ongoing studies of inter‐site and inter‐island interaction. This paper reviews the dating of 28 wood and shell artefacts from sites in northern Cuba in an attempt to date pre‐Columbian activity in the region and develop dating methodologies for the study of pre‐Columbian interaction in the Caribbean. This research compares dates from wood and shell artefacts from the waterlogged site of Los Buchillones in north‐central Cuba with dates from shell artefacts from sites on eight islands in the Sabana–Camaguey archipelago in the Bahama Channel. In addition to providing a chronological framework based on absolute dates for pre‐Columbian activity in northern Cuba, this paper also considers the methodological issues of using shell for dating pre‐Columbian activity in the Caribbean.     

Tephrochronology,Environmental Change and the Norse Settlement of Iceland

Abstract

The first human impacts on the Icelandic environment came with the Norse colonisation or Landnám of the ninth century AD. The colonisation represents a fundamental environmental change that is both rapid and profound. In this paper we assess geomorphological dimensions of the initial settlement period using a tephrochronology that includes the Landnám Tephra, erupted ca. 870 AD, two tenth century AD tephras KR 920 and E 935, and 11 other well dated tephra layers. We report a new ¹⁴C age of 1676 ±12 ¹⁴C yr BP (cal AD 345 (400) 419) for the tephra SILK-YN which forms a key prehistoric marker horizon that constrains rates of environmental change in the centuries before Norse Settlement. Aeolian sediment accumulation rates show five geomorphological responses to settlement that differ in the rate and trajectory of change. These distinct anthropogenic signals are the result of spatially variable sensitivity to grazing and deforestation, and reflect the extent of local soil erosion. This critical erosion threshold is variable in space and time.     

RADIOCARBON DATES FROM THE OXFORD AMS SYSTEM: ARCHAEOMETRY DATELIST 34

This is the thirty‐fourth list of AMS radiocarbon determinations measured at the Oxford Radiocarbon Accelerator Unit (ORAU). Amongst the dates obtained for archaeological sites included here are the latest series of determinations from the key sites of Proskynas (Greece), Kova?evo (Bulgaria) and Khirbet Qeiyafa (Israel), as well as others dating to the Palaeolithic, Mesolithic and later periods. Submitters of the material provide comments on the significance of the results.     

ESR Dating of Tooth Enamel: Comparison with AMSC at El Castillo Cave, Spain

At El Castillo, in Cantabrian Spain, uncalibrated AMS¹⁴C dating has shown the transition from Mousterian to Aurignacian to occur at 39·3±1·6 kaBP. We found ESR tooth enamel ages from the basal Aurignacian level at El Castillo to be 36·2±4·1 ka (early and linear uptake). The enamel and dentine had very low U contents, but ESR ages are strongly dependent upon knowledge of the moisture content history of the sediments. Although the Aurignacian ESR age is 8% younger than the weighted average uncalibrated AMS¹⁴C age of 39·6±1·3 ka obtained from charcoal samples, we have shown that the methods agree within experimental uncertainty. However, since no precise¹⁴C calibration yet exists for this period of time, we are unable to specify which of the ages is more accurate, nor are we able ascribe the apparent age discrepancy to a particular deficiency in the ESR method.     

TL DATING OF BURNT LITHICS FROM BLOMBOS CAVE (SOUTH AFRICA): FURTHER EVIDENCE FOR THE ANTIQUITY OF MODERN HUMAN BEHAVIOUR*

This paper presents the first TL dates for burnt quartzites and silcretes from the Still Bay layers of Blombos Cave (South Africa). These layers contained engraved ochres and marine shell beads that could be an early manifestation of symbolic and thus ‘modern’ behaviour by the Middle Stone Age humans. The procedure devised to calculate the ages is presented in detail, particularly with regard to internal microdosimetry, because the problems faced in estimating the dose rates require an approach different from the one usually used on flints and sediments. A mean age of 74 ± 5 ka was obtained for five burnt lithics unearthed in the BBC M1 member of the Still Bay layers. This result is in good agreement with both ESR dates on teeth and OSL dates on sediment, and demonstrates the great antiquity of the archaeological remains discovered at Blombos Cave.