Proceedings of the 19th International Radiocarbon Conference

ultrafiltration of bone collagen provides a method of purification that can be very effective in reducing environmental contamination from soil-derived amino acids as well as removing degraded collagen or other short-chain proteins. The Oxford Radiocarbon Accelerator Unit (ORAU) first implemented ultrafiltration in the pretreatment of bone material for accelerator mass spectrometry (AMS) radiocarbon dating in 2000. However, the filters themselves contain carbonaceous material, and thus stringent quality control is required to demonstrate that this does not affect the accuracy of the dating. Here, the authors present quality assurance data from the bone pretreatment and dating program at ORAU, including dates on known-age and background-age bones over a range of sample sizes, and measurements of residual carbon contamination present in the filters after cleaning

in the sample preparation laboratory of CEDAD (CEnter for DAting and Diagnostics) of the University of Lecce, a protocol for the quality control of bone samples based on infrared spectroscopy has been set up. The protocol has been recently developed as a check-in test with the aim to identify the presence of collagen in the samples, assess its preservation status, and determine whether the submitted bone samples are suitable for accelerator mass spectrometry (AMS) radiocarbon measurements or not. The authors discuss the use of infrared-based techniques to identify the presence of `contaminants' such as restoration and consolidation materials, humic acids, and soil carbonates, which, if not removed by the sample processing chemistry, can be sources of exogenous carbon and can thus influence the accuracy of the 14C determinations. Bone samples recovered in well-defined and previously dated archaeological contexts were intentionally contaminated, submitted to the standard method for collagen extraction and purification, and then characterized by means of Fourier transform infrared (FTIR) spectroscopy analyses performed in attenuated total reflection (ATR) mode before being combusted, converted to graphite, and measured by AMS. The study shows that the ATR-FTIR technique is an extremely powerful method for the identification of both the collagen and its contaminants and can supply important information during the selection and processing of samples to be submitted for 14C dating

the authors studied the requirements for producing accurate and reliable dates by high-sensitivity liquid scintillation (LS) spectroscopy beyond 50 kyr. Laboratory procedures include optimization of LS spectrometers to obtain low and stable non-14C background count rates, use of low-background counting vials, large benzene volumes, long counting times, and preconditioning of vacuum lines. They also discuss the need for multiple analyses of a suitable material containing no original 14C (background blank) and the application of an appropriate statistical model to compensate for variability in background contamination beyond counting statistics. Accurate and reproducible finite ages >60 kyr are indeed possible by high-sensitivity LS spectroscopy, but require corroborating background blank data to be defensible

as a general investigation of the radiocarbon dating of cremated bone since its initial development, a small, cremated bone intercomparison study took place in 2005, involving six laboratories. Six cremated bone samples (including two sets of duplicates), with ages spanning approximately 1500--2800 BP, were sent to the laboratories. The results, which showed relatively good agreement amongst the laboratories and between the duplicate samples, are discussed in detail

the paper introduces some of the most important terms commonly used in 14C dating and explains, through some simple examples, their interpretation

the paper outlines the radiocarbon program applied to the excavation and skeletal assemblage from the cemetery of the medieval Priory and Hospital of St Mary Spital in London. Problems encountered in dating medieval cemeteries are outlined. The problems were addressed through the application of Bayesian modeling to validate and refine conventional approaches to constructing phases of archaeological activity. It should be noted that this project was solely funded by the developer of the land; such projects rarely undertake even modest programs of 14C dating. The authors aim to show how the investment of a proportionally small sum, compared to the overall project costs, may reap significant benefits

recent work in Loch Tay has resulted in 14C dating of the timber piles from thirteen of the eighteen crannogs in the loch, allowing them to be fitted into different classes. A major group was constructed in the Early Iron Age around 400--800 BC, with smaller groups constructed around 200--300 BC and 0 BC/AD. There is also evidence of repair/reoccupation of some of these crannogs in the sixth to ninth centuries AD. A number of the sites were also known to be inhabited into the recent past, with one, Priory Island, occupied until the seventeenth century. The dates of construction also raise important issues relating to the loch-level changes that have taken place. The 14C results are discussed in relation to the periods of origin and habitation of the crannogs

high-precision radiocarbon age calibration for different terrestrial samples allows the establishment of accurate boundaries for many climatic time series. At the same time, the fluctuations of 14C content reflect solar variability. A bispectrum analysis of long-term series of the 14C content deduced from decadal measurements in tree rings demonstrates the existence of amplitude modulation, with a period of main modulation of ~2400 yr. In 14C time series for the last 11 kyr, major oscillations are distinguished at 8.5--7.8, 5.4--4.7, 2.6--2.2, and 1.1--0.4 cal kyr BP with ~2400-yr periodicity. High amplitudes in cosmogenic isotope content with a periodicity of about 2400 yr appear synchronous to cooling events documented in Greenland ice cores, to the timing of worldwide Holocene glacier expansion, and to the periods of lake-level changes. The paper focuses on revealing solar forcing on the Earth's climate and about the nature, significance, and impact of sharp Holocene climate variability on human societies and civilizations

rivers and streams in many parts of the world contain high concentrations of dissolved carbon dioxide, which is lost to the atmosphere by evasion (outgassing). Recent methodological advances now enable the carbon isotopic composition of this evaded CO2 to be measured directly, with early results from peatland streams showing it to be depleted in 13C relative to the atmosphere. The first direct measurements of the radiocarbon age of evaded CO2 for a stream draining a peatland site in the United Kingdom covered a large range, ranging from modern to >1400 yr BP. The authors investigated whether a proportion of the carbon fixed by plants growing adjacent to the stream was derived from evasion; this would have implications for the cycling of carbon in such streams, and lead to riparian plants having older, rather than contemporary, 14C ages. 13C analysis of riparian plants at the site suggested that up to 20% of the carbon they fixed was derived from evasion. Although the 14C content of the same samples suggested a similar proportion of plant carbon was derived from evaded CO2, the uncertainty in these estimates was greater. Fixation of evaded CO2 was greatest in plants growing within 1m of the stream. Although the results for this site suggest a small amount of CO2 lost by evasion from the stream surface is incorporated in plant material, it may be a more important factor at other sites characterized by higher evasion rates, lower wind speeds, and different stream bank morphology