• A Database System for Geochemical, Isotope Hydrological, and Geochronological Laboratories

      Suckow, Axel; Dumke, Ingolf (Department of Geosciences, The University of Arizona, 2001-01-01)
      We present a data model designed for laboratories in which many different methods are used. The main feature of the model is the recursive relationships of data records in the subsample table. This makes it possible to model all steps from the preparation of the sample to the final value and enables the raw data to be stored together with the final values, even if many preparation steps or many subsamples are involved. We show ways to adopt this basic model to laboratories with many years of data. The data model is extended to include laboratory records and attribute data, e.g. The geographical coordinates of the sampling site or links to the various projects for which the samples are used.
    • A Fresh Water Diet-Derived 14C Reservoir Effect at the Stone Age Sites in the Iron Gates Gorge

      Cook, Gordon T.; Bonsall, C.; Hedges, Robert E. M.; McSweeney, K.; Boronean, V.; Pettitt, Paul B. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Human bones from single inhumation burials and artifacts made from terrestrial mammal (ungulate) bone found in direct association with the skeletons were obtained from the Stone Age site of Schela Cladovei situated just below the Iron Gates Gorge of the River Danube. The results of stable isotope analyses of the human bone collagen are consistent with a heavy dependence on aquatic protein while radiocarbon dating of the samples reveals an offset of 300-500 years between the two sample types, indicating a freshwater reservoir effect in the human bone samples. Since protein consumption is by far the major source of nitrogen in the human diet we have assumed a linear relationship between delta-15N and the level of aquatic protein in each individual's diet and derived a calibration for 14C age offset versus delta-15N which has been applied to a series of results from the site at Lepenski Vir within the gorge. The corrected 14C ages (7310-6720 BP) are now consistent with the previous 14C age measurements made on charcoal from related contexts (7360-6560 BP). In addition, the data indicate a change from a primarily aquatic to a mixed terrestrial/aquatic diet around 7100 BP and this may be argued as supporting a shift from Mesolithic to Neolithic. This study also has wider implications for the accurate dating of human bone samples when the possibility exists of an aquatic component in the dietary protein and strongly implies that delta-15N analysis should be undertaken routinely when dating human bones.
    • A Marine Reservoir Data Correction Database and On-Line Interface

      Reimer, Paula J.; Reimer, Ron W. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Calibration is essential for interpretation of radiocarbon dates, especially when the 14C dates are compared to historical or climatic records with a different chronological basis. 14C ages of samples from the marine environment, such as shells or fish bones, or samples with a marine component, such as human bone in coastal regions, require an additional consideration because of the reservoir age of the ocean. While the pre-industrial global mean reservoir correction, R(t), is about 400 years, local variations (Delta-R) can be several hundred years or more. Delta-R compilations on a global scale have been undertaken previously (Stuiver et al. 1986; Stuiver and Braziunas 1993), but have not been updated recently. Here we describe an on-line reservoir correction database accessed via mapping software. Rather than publishing a static Delta-R compilation, new data will be incorporated when it becomes available. The on-line marine reservoir correction database can be accessed at the website http://www.calib.org/.
    • A Special Dedication to Israel Carmi

      Boaretto, Elisabetta (Department of Geosciences, The University of Arizona, 2001-01-01)
    • Accelerator Mass Spectrometry at High Voltage Engineering Europa (HVEE)

      Gottdang, A.; Klein, M.; Mous, D. J. W. (Department of Geosciences, The University of Arizona, 2001-01-01)
      In recent years, High Voltage Engineering Europa (HVEE) has demonstrated its capability of developing and installing turnkey accelerator mass spectrometry (AMS) equipment for the analysis of, among others, 14C and 129I. Five 3MV systems using sequential and/or simultaneous injection are operational in the field today, and they have shown excellent long-term stability providing high-precision analyses on a routine basis. Another three AMS systems are in production. It is projected that for the time being, AMS will continue to broaden its field of applications; a saturation of the market of AMS facilities is not expected in the near future. To meet the specific demands of the biomedical research community, we have developed an extreme compact 14C AMS system comprising a hybrid ion source capable of handling both graphite as well as CO2 samples. The source is optimized for easy maintenance, accommodates up to 200 samples, and can be implemented in any other AMS system. More recently, HVEE has initiated the development of an AMS system capable of detecting, among others, 36Cl and 41Ca. The design will include a HVEE 5MV Tandetron(TM). The accelerator is currently under construction as part of an ion beam analysis system for the Universidad Autonoma de Madrid (Spain).
    • Acknowledgments of Financial Support

      Department of Geosciences, The University of Arizona, 2001-01-01
    • AMS Radiocarbon Dating of Ancient Iron Artifacts: A New Carbon Extraction Method in Use at LLNL

      Cook, Andrea C.; Wadsworth, Jeffrey; Southon, John R. (Department of Geosciences, The University of Arizona, 2001-01-01)
      A new sealed double tube combustion method was developed at Lawrence Livermore National Laboratory (LLNL) to extract carbon from modern steels and ancient iron artifacts. Iron samples were chemically pretreated with 10% nitric acid, vacuum sealed in 6 mm quartz tubes with CuO, vacuum sealed again inside 9 mm quartz tubes, and combusted at 1000 degrees C for a minimum of 10 hr. The resulting CO2 was graphitized routinely using hydrogen reduction (Vogel et al. 1989). After the initial phase of development, carbon yields of 100% were consistently obtained. The activities of two modern high carbon steels (treated as process blanks, manufactured using only coal as the carbon source) were determined to be 0.0077 +/0.0009 (n = 12, +/1 sigma) for a 1.3% C steel and 0.0090 +/0.0038 (n = 12, +/1 sigma) for a 1.9% C steel, indicating that very little contamination is introduced during the sample preparation process. Since the Iron Age began less than 5000 years ago, these background uncertainties should introduce errors of no more than +/30 years to the radiocarbon ages of actual artifacts. Two ancient iron artifacts of known date were analyzed and demonstrate that the new methodology can be used to obtain the correct date of manufacture for iron objects, provided that they are made exclusively using charcoal that was contemporaneous with the manufacture of the artifact. Since only 1 mg of carbon is required for accelerator mass spectrometry (AMS), very small iron samples can now be analyzed (50 mg of a 2.0% C iron or 1 g of a 0.1% C iron). We anticipate that this methodology will be particularly useful to archeologists who currently have to rely on context to date iron artifacts.
    • An Extraction System to Measure Carbon-14 Terrestrial Ages of Meteorites with a Tandetron AMS at Nagoya University

      Minami, Masayo; Nakamura, Toshio (Department of Geosciences, The University of Arizona, 2001-01-01)
      We have constructed a system to extract carbon from meteorites using a vacuum-tight RF melting method in order to study radiocarbon activities in meteorites. The extraction system was examined using iron standards of known carbon content. The carbon extraction efficiencies and 14C ages of the iron standards by this method were compared with the results obtained previously by our older melting system and a wet oxidation method. Higher collection efficiencies of about 90% for the iron samples of relatively high carbon content were achieved by the new system. The efficiency of extracting a small amount of carbon is also near 90% after improving the extraction procedure. The 14C ages of the iron standards were compared to the ages by the wet method. The results indicate that contamination by modern carbon is negligible in the system. Furthermore, terrestrial 14C ages of two Antarctic meteorites, Y-75102 and ALH-77294, from the Yamato and Allan Hills ice fields, respectively, were determined. The age of Y-75102 is estimated 4.0 +/1.0 ka, and the age of ALH-77294 is 19.5 +/1.2 ka. The 14C ages on the meteorites roughly agree with the literature value. However, further study is needed in improvement on reducing a background value and of complete fusion of a meteorite in the extraction system.
    • An Improvement in Preparation of Mortar for Radiocarbon Dating

      Sonninen, E.; Jungner, H. (Department of Geosciences, The University of Arizona, 2001-01-01)
      An error source in radiocarbon dating of ancient mortar is dead carbon of limestone mixed in the matrix. To eliminate the influence of limestone the difference in feasibility to react with acid between mortar and limestone is used. Since the rate of reaction depends on grain size use of a well-defined grain size can give a better separation between mortar and limestone. We present results for the grain size dependence of reaction rates for several mortar and limestone samples and discuss the application for dating.
    • Automatic AMS Sample Combustion and CO2 Collection

      Aerts-Bijma, A. T.; van der Plicht, J.; Meijer, H. A. J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      In Groningen, all organic samples for accelerator mass spectrometry (AMS) are combusted in an automatic Elemental Analyzer, coupled to an Isotope Ratio Mass Spectrometer and Cryogenic Trapping System. The Gas Chromatographic (GC) column, part of the Elemental Analyzer system, appeared to be the main cause for memory effects. Therefore we modified the Elemental Analyzer, such that the trapped CO2 no longer passed the GC column. Our system modification reduced the memory effect significantly, as shown by lower radiocarbon concentration values for anthracite backgrounds, and a much smaller spread in these values. Our modified system can perform up to 40 combustions unattended in about 6 hr.
    • Carbonate 14C Background: Does It Have Multiple Personalities?

      Nadeau, Marie-Josée; Grootes, Pieter M.; Voelker, Antje; Bruhn, Frank; Oriwall, Alexander (Department of Geosciences, The University of Arizona, 2001-01-01)
      Measurements of the radiocarbon concentration of several carbonate background materials, either mineral (IAEA C1 Carrara marble and Icelandic double spar) or biogenic (foraminifera and molluscs), show that the apparent ages of diverse materials can be quite different. Using 0.07 pMC obtained from mineral samples as a processing blank, the results from foraminifera and mollusc background samples, varying from 0.12 to 0.58 pMC (54.0–41.4 ka), show a species-specific contamination that reproduces over several individual shells and foraminifera from several sediment cores. Different cleaning attempts have proven ineffective, and even stronger measures such as progressive hydrolization or leaching of the samples prior to routine preparation, did not give any indication of the source of the contamination. In light of these results, the use of mineral background material in the evaluation of the age of older unknown samples of biogenic carbonate (>30 ka) proves inadequate. The use of background samples of the same species and provenance as the unknown samples is essential, and if such material is unavailable, generic biogenic samples such as mixed foraminifera samples should be used. The description of our new modular carbonate sample preparation system is also introduced.
    • Chemical Removal of Conservation Substances By 'Soxhlet'-Type Extraction

      Bruhn, Frank; Duhr, Alexander; Grootes, Pieter M.; Mintrop, Annette; Nadeau, Marie-Josée (Department of Geosciences, The University of Arizona, 2001-01-01)
      At the Leibniz radiocarbon lab, art and archaeological objects, often chemically conserved and thus potentially contaminated with respect to their 14C content, are treated using a computer-controlled “Soxhlet”-type series extractor. This device uses a continuous procedure of boiling and condensation of different solvents for extraction and vacuum filtration under constant process conditions. An elutrope sequence of five solvents that dissolve most customary conservation chemicals was selected. A study of these different contaminants applied to reference wood samples with subsequent accelerator mass spectrometry (AMS) measurements demonstrates that their effective removal is dependent on the use of adequate solvents. For many contaminants (e.g. Wood glue, methyl cellulose, Klucel(R), sugar, and polyethylene glycol), routine acid-alkali-acid (AAA) treatment already yields satisfactory results, whereas for Caparol(R) and beeswax a relatively “mild” treatment with acetone, methanol, water, and subsequent standard AAA extraction is sufficient. Complete removal of rubber glue, epoxyresin, and paraffin can only be accomplished with our full set of solvents. The latter procedure is also appropriate when no or only incomplete information about the type of conservation material is available. For epoxy resin the contamination appears to be enriched in the alkali residue, and the easily soluble “humic acid” fraction, even after standard AAA treatment, gives satisfactory results. Two case studies on the application of the extraction procedures are presented.
    • Conference Participants

      Department of Geosciences, The University of Arizona, 2001-01-01
    • Converting AMS Data to Radiocarbon Values: Considerations and Conventions

      McNichol, A. P.; Jull, A. J. T.; Burr, G. S. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We summarize the basic operation of accelerator mass spectrometry (AMS) systems used to measure radiocarbon and discuss the calculations used to convert AMS output to 14C data.
    • Cosmic Background Reduction in the Radiocarbon Measurement By Scintillation Spectrometry at the Underground Laboratory of Gran Sasso

      Plastino, Wolfango; Kaihola, Lauri; Bartolomei, Paolo; Bella, Francesco (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon measurements by two 1220 Quantulus(TM) ultra low background liquid scintillation spectrometers were performed at the underground laboratory of Gran Sasso and the Radiocarbon Laboratory of E.N.E.A.-Bologna to study the efficiency and background variations related to measurement sites. The same configuration setup, i.e. The same center of gravity of the 14C spectrum (SQP(I) = 410 +/1) was obtained in both instruments. Many different background and modern standards with pure analytical benzene were used and spectra for 40 one-hour periods were obtained. The data indicates a background reduction of approximately 65% between the surface and underground laboratories, with no differences in the efficiency. Recording similar efficiencies in both spectrometers is probably due to fairly identical photomultiplier characteristics. The cosmic noise reduction observed at the laboratory of Gran Sasso makes it possible to perform high precision 14C measurements and to extend for these idealized samples the present maximum dating limit from 58,000 BP to 62,000 BP (5 mL, 3 days counting).
    • Dating of Cremated Bones

      Lanting, J. N.; Aerts-Bijma, A. T.; van der Plicht, J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      When dating unburnt bone, bone collagen, the organic fraction of the bone, is used. Collagen does not survive the heat of the cremation pyre, so dating of cremated bone has been considered impossible. Structural carbonate in the mineral fraction of the bone, however, survives the cremation process. We developed a method of dating cremated bone by accelerator mass spectrometry (AMS), using this carbonate fraction. Here we present results for a variety of prehistoric sites and ages, showing a remarkable success rate for this method.
    • Delta-R Correction Values for the Northern Indian Ocean

      Dutta, Koushik; Bhushan, Ravi; Somayajulu, B. L. K. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Apparent marine radiocarbon ages are reported for the northern Indian Ocean region for the pre-nuclear period, based on measurements made in seven mollusk shells collected between 1930 and 1954. The conventional 14C ages of these shells range from 693 +/44 to 434 +/51 BP in the Arabian Sea and 511 +/34 to 408 +/51 BP in the Bay of Bengal. These ages correspond to mean Delta-R correction values of 163 +/30 yr for the northern Arabian Sea, 11 +/35 yr for the eastern Bay of Bengal (Andaman Sea) and 32 +/20 yr for the southern Bay of Bengal. Contrasting reservoir ages for these two basins are most likely due to differences in their thermocline ventilation rates.
    • Dendrochronology and Radiocarbon Dating Methods in Archaeological Studies of Scythian Sites

      Dergachev, Valentin A.; Vasiliev, S. S.; Sementsov, A. A.; Zaitseva, Ganna I.; Chugunov, K. A.; Sljusarenko, I. Ju (Department of Geosciences, The University of Arizona, 2001-01-01)
      We propose a new method of cross-dating the wood samples based on the classical methods of spectral estimation. This method uses the average cross-spectral density as a function of the relative position of the series. Because it is not sensitive to phase shifts in data it is appropriate for cross-dating samples originating from geographically distinct areas. The accuracy of cross dating depends on the integrity of the samples used, and in the case of well-preserved wood samples, the precision of relative age comparison may reach a single year. The method was tested on two dendrochronological series from Scythian barrows of known age in Southern Siberia: the Pazyryk barrows (the Altai Mountains) and the Dogee-Baary -2 burials (Western Sayan Mountains) separated by 450 km. The analysis has shown that the Pazyryk barrow is younger by 80 +/4 yr than the Dogee-Baary -2 burials. This result is in agreement with the new chronology of Scythian-related sites suggested for Southern Siberia and Central Asia.
    • Development of a Semi-Automated System for Routine Preparation of Carbonate Samples

      Tisnérat-Laborde, N.; Poupeau, J. J.; Tannau, J. F.; Paterne, M. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We constructed a semi-automated system to transform carbonate samples to CO2, as a means to increase sample-processing capacity. The physicochemical process includes hydrolysis of carbonate, quantification of the mass of carbon and CO2 collection in a glass ampoule. The system is computer-controlled and monitored, and all the data are stored. A single run of five consecutive samples requires about 3.5 hours. Measurements of 14C concentrations were made on samples of IAEAC-1 Carrara marble to test the reliability of this semi-automated system. These measurements have allowed the determination of the total system background and the memory effect of our system.
    • Development of the Radiocarbon Calibration Program

      Bronk Ramsey, Christopher (Department of Geosciences, The University of Arizona, 2001-01-01)
      This paper highlights some of the main developments to the radiocarbon calibration program, OxCal. In addition to many cosmetic changes, the latest version of OxCal uses some different algorithms for the treatment of multiple phases. The theoretical framework behind these is discussed and some model calculations demonstrated. Significant changes have also been made to the sampling algorithms used which improve the convergence of the Bayesian analysis. The convergence itself is also reported in a more comprehensive way so that problems can be traced to specific parts of the model. The use of convergence data, and other techniques for testing the implications of particular models, are described.