Prof Christopher Ramsey

Abstract:

Radiocarbon dating of individual samples only yields limited chronological precision (typically of the order of 150–200 years for 95% confidence). This is in large part due to the complex nature of the calibration curve. Only by using large numbers of radiocarbon determinations together can we hope to resolve chronological issues at the sub-century level. Interpretation of such datasets is very difficult to do accurately by eye and for this reason statistical methods are needed. The methods most often employed are those of Bayesian analysis. Such methods do indeed allow us to improve our precision beyond that which is possible for single age determinations by radiocarbon but, critically, they also allow us to see the limitations in our data. In cases where statistical analysis shows that the radiocarbon measurements cannot resolve the chronological issues we need to accept that we must rely on other forms of archaeological information and interpretation. The conference at Yarnton was very closely focussed on specific chronological issues in the Iron Age of the Levant. These issues are of critical importance to the understanding of the interrelationship of the polities of the region and would be of academic interest in any other region under archaeological investigation. However, in this case the arguments are given even more prominence because of the implications for our interpretation of the nature of King Solomon's political impact.

Abstract:

A series of AMS radiocarbon determinations have been obtained from the site of Khirbet-en-Nahas, Jordan. An initial suite of samples dated in Oxford and a subsequent and much larger suite from Groningen were obtained to determine the onset of copper and iron production in the Faynan district. The determinations came from two different areas at the site. Bayesian modeling was used to improve the chronometric resolution. This showed that copper production expanded from ca. 950 BCE. The challenge at sites such as this is to obtain samples of short-lived age and thereby avoid ‘inbuilt age’. Several of the AMS determinations were, in all likelihood, affected by this, and the Bayesian modeling enabled us to determine outliers and question their reliability. Further work is planned. This chapter concerns the analysis of the radiocarbon chronology of Khirbat en-Nahas (hereafter KEN), Jordan, the largest Iron Age copper production site in the Faynan district. It is, therefore, a partial contribution to the Jabal Hamrat Fidan Project, which is engaged in extensive archaeological investigations in this region. Details of the archaeology of the site is discussed elsewhere in this volume (Levy et al. [Chapter 10, this volume]) and in a recent publication (Levy et al. 2004). The aims of the radiocarbon dating program were initially focussed upon two key areas. First, to date one of the large buildings and part of a gate complex at the site.

Abstract:

The stratified series of Iron Age radiocarbon dates from Tel Reh?ov, based on short-lived samples, measured in Groningen, is the most detailed and dense chronometric record currently available for the Levant in this period. The more detailed IntCal98 calibration curve was used, though some comparisons were made with the smoothed IntCal04 curve. The current Bayesian stratigraphic model for Tel Reh?ov gave a number of significant results. The data strongly favour an early Iron Age IB-IIA transition, as the statistically sampled boundary in the 1s range is 992-961 BCE (68.2%). Considering the 2s range, the older time option, 998-957 BCE, further increases in probability to 75.2%, but a second option also appears, 953-921 BCE, albeit with a significantly lower relative probability of 20.2%. Our Bayesian model was also tested with the IntCal04 calibration curve, which gave similar but slightly older results: the 1s range is 993-961 BCE (68.2%) and the 2s range is 1001-927 BCE (95.4%). The peak probability remains the same at ca. 970 BCE. The Stratum VI dates have the most likely position within the 1s range 971-958 BCE (62.4%). The City of Stratum V had a possible duration of 26 to 46 years, in the 1s and 2s ranges, respectively. The 1s sampled destruction of City V is 924-902 BCE (68.2%). This time range could fit a possible association with the Asian campaign of Shoshenq I (Shishak), solely based on Egyptian criteria (see Shortland [Chapter 4, this volume]). Running the Bayesian model with the IntCal04 calibration curve yielded a slightly older date in the 1s range: 929-906 BCE (68.2%). The latter range does include the date 925 BCE for the Shoshenq campaign as suggested by Kitchen (1986, 2000). The City of Stratum IV had a possible duration of 28-55 years, in the 1s and 2s ranges, respectively. The 1s sampled destruction of City IV is 903-892 (13.4%), 885-845 BCE (54.8%). Thus, the Bayesian statistical computation results of the Tel Reh?ov stratigraphic model generally strengthen earlier conclusions concerning a revised traditional chronology, and do not indicate support for the low chronology viewpoint.

Abstract:

The eruption of the volcano at Thera (Santorini) in the Aegean Sea undoubtedly had a profound influence on the civilizations of the surrounding region. The date of the eruption has been a subject of much controversy because it must be linked into the established and intricate archaeological phasings of both the prehistoric Aegean and the wider east Mediterranean. Radiocarbon dating of material from the volcanic destruction layer itself can provide some evidence for the date of the eruption, but because of the shape of the calibration curve for the relevant period, the value of such dates relies on there being no biases in the data sets. However, by dating the material from phases earlier and later than the eruption, some of the problems of the calibration data set can be circumvented and the chronology for the region can be resolved with more certainty. In this paper, we draw together the evidence we have accumulated so far, including new data on the destruction layer itself and for the preceding cultural horizon at Thera, and from associated layers at Miletos in western Turkey. Using Bayesian models to synthesize the data and to identify outliers, we conclude from the most reliable 14C evidence (and using the INTCAL98 calibration data set) that the eruption of Thera occurred between 1663 and 1599 BC.

Abstract:

Bone is one of the most widely used materials for dating archaeological activity. It is also relatively difficult to pretreat effectively and new methods are an area of active research. The purpose of the chemical pretreatment of bone is to remove contaminants present from burial and to do so in a way which does not add any additional laboratory contaminant. To some extent, these two aims must be balanced since, on the whole, the more complex the procedure and the more steps included, the greater the chance for contamination. At the Oxford Radiocarbon Accelerator Unit (ORAU), the method used is a continuous-flow or manual acid/base/acid (ABA) treatment followed by gelatinization and ultrafiltration (based on Brown et al. [1988]; documented in Bronk Ramsey et al. [2000]). We find this overall method is very effective at removing more recent contamination in old bones. However, two aspects of the method have recently been improved and are reported here: the redesign of ORAU's continuous flow pretreatment and a new protocol in our pretreatment ultrafiltration stage.