• Dating the Turin Shroud—An Assessment

      Gove, H. E. (Department of Geosciences, The University of Arizona, 1990-01-01)
      An assessment is made of the credibility of the radiocarbon dating of the shroud of Turin. The quoted final results produced a calibrated calendar age range of AD 1260–1390 for the linen of the Turin shroud at a 95% confidence level. The measurements were carried out independently in three accelerator mass spectrometry (AMS) laboratories located at the University of Arizona, Tucson, Arizona, USA, Oxford University, Oxford, England, and ETH-Hönggerberg, Zürich, Switzerland with assistance for certification and data analysis provided by the British Museum. The author concludes that, although the procedures followed differed substantially from those recommended at a workshop organized by the Pontifical Academy of Sciences, the results are credible. Although of negligible scientific value, they represent a major public triumph for the AMS method of carbon dating. However, many doubts have been raised, both real and fanciful, concerning the validity of the results and these are discussed. It is suggested that steps should be taken to conserve the shroud and that permission should be given for its examination by experts in medieval art.
    • Discussion: Recovery from Tracer Contamination in AMS Sample Preparation

      Jull, A. J. T.; Donahue, Douglas J.; Toolin, L. J. (Department of Geosciences, The University of Arizona, 1990-01-01)
    • Further Investigations on 14C Dating of Calcareous Tufa

      Pazdur, Anna; Pazdur, Mieczysław F. (Department of Geosciences, The University of Arizona, 1990-01-01)
      Systematic studies on 14C dating of tufa profiles in southern Poland have resulted in developing a simple phenomenological model which enables us to estimate the reservoir correction factor of 14C dates of individual carbonate samples. We made further studies to test model assumptions and to verify relationships between the value of reservoir correction factor TR and 13C content of tufa carbonate. Two new study sites, Rudawa and Szklarka, are close to previously studied sites. Four tufa samples with associated organic fraction from ca 2000m asl in South America (Peruvian Andes) were measured to test the possible application of the developed model to tufas in different geochemical and climatic environments. Finally, a series of calcareous tufa samples from the Villers-devant-Orval profile (Belgium) were dated, although no direct comparison with organic matter dates is available for this profile.
    • Memory Effects in an AMS System: Catastrophe and Recovery

      Vogel, J. S.; Southon, J. R.; Nelson, D. E. (Department of Geosciences, The University of Arizona, 1990-01-01)
      A sample with a 14C concentration estimated to be greater than 30,000 Modern was inadvertently graphitized and measured in an AMS system. No measurable contamination of the cesium sputter ion source was observed. Simple cleaning procedures removed the contamination from the sample preparation system, with the exception of the reaction vessel in which the sample was graphitized. Sample cross-contamination factors were estimated for all of the preparation and measurement procedures.
    • Operation of the Harwell UK 14C Data Base and Its Expansion Through Data Exchange with Other Laboratories

      Walker, A. J.; Otlet, R. L.; Housley, R. A.; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 1990-01-01)
      The use of computer data bases for storage and retrieval of 14C data is a logical application for the rapidly expanding numbers of 14C determinations. Harwell has established a data base for all samples originating from sites in the United Kingdom and Eire. The core of the data is the Council for British Archaeology's published Index of Radiocarbon Dates which we are expanding to include all Harwell UK dates released for publication by the submitters plus dates from other laboratories both within and outside the UK. As a demonstration of the feasibility of direct database-to-database communication, cooperation has been sought from Groningen and Oxford to transfer computer files containing 14C results for UK sites. Neither of these laboratories use the same system as Harwell for their in-house data base and this exercise highlights the importance of a transfer language for both the national and international schemes as it is no longer practical to carry out such procedures through keyboard typing.
    • Re-Evaluation of British Museum Radiocarbon Dates Issued Between 1980 and 1984

      Bowman, S. E.; Ambers, J. C.; Leese, M. N. (Department of Geosciences, The University of Arizona, 1990-01-01)
      Dates issued by the British Museum radiocarbon laboratory between 1980 and 1984 are known to have been in error. This paper outlines the cause of the problem and the procedures adopted to revise the results affected. Where revision has been possible, on average this has given dates older by 200 to 300 radiocarbon years. The individual revised results are tabulated.
    • Some Radiocarbon Dates for Tufas of the Craven District of Yorkshire

      Pentecost, Allan; Thorpe, P. M.; Harkness, D. D.; Lord, T. C. (Department of Geosciences, The University of Arizona, 1990-01-01)
      14C dates of relict tufa deposits at Gordale indicated a Subboreal age when the carbonate age was corrected with empirical bedrock dilution factors ‘q’ of 0.79 or 0.85. Estimates of ‘apparent age,’ based on extrapolated Delta-13C values were about twice those obtained with q, and the 1 sigma error was large. The Delta--13C values of tufa samples were not correlated with carbonate age and were close to −10. Application of q values in this district requires caution as they appear to be site-specific. We recommend that wherever possible, levels of 13C and 14C are measured in the associated tufa-depositing water, and an empirical dilution factor employed.
    • Superconducting Mini-Cyclotrons as AMS Instruments

      Subotic, K. M.; Milinkovic, L. S.; Zupancic, M. T.; Novkovic, D. N.; Stojanovic, M. S. (Department of Geosciences, The University of Arizona, 1990-01-01)
      We have studied the limitations of conventional mass spectrometry and have examined accelerator based methods which could help circumvent these limitations. In particular, cyclotron-based accelerator mass spectrometric (AMS) techniques are discussed with an emphasis on evaluating performances of superconducting mini-cyclotrons designed for use as AMS instruments. We discussed the design of superconducting mini-cyclotrons dedicated to radioisotope dating research.
    • Survey of the Dispersion of 14C in the Vicinity of the UK Reprocessing Site at Sellafield

      Otlet, R. L.; Walker, A. J.; Fulker, M. J. (Department of Geosciences, The University of Arizona, 1990-01-01)
      We have been measuring 14C in natural, biological materials growing in the vicinity of Sellafield, Cumbria as a continuing project with BNFL to understand the dispersion of releases from the site over several seasons. We have measured locally grown foodstuffs for monitoring purposes, individual tree rings to establish a chronology of releases, hawthorn berries for spatial investigations and are now carrying out controlled plot uptake experiments. We have been attempting to validate a current dispersion model (Clarke 1979) over a six-year period, and although we observe general agreement in most years, certain anomalies, which probably relate to topographical features, are leading to more detailed correlation with local meteorological data.