• 14C Ages of 43 Consecutive Single-Year Tree Rings Between 2710 and 2655 cal BP Using Accelerator Mass Spectrometry

      Suzuki, Kayo; Sakurai, Hirohisa; Takahashi, Yui; Gunji, Shuichi; Tokanai, Fuyuki; Matsuzaki, Hiroyuki; Sunohara, Yoko (Department of Geosciences, The University of Arizona, 2007-01-01)
      We have measured the radiocarbon ages of 43 consecutive single-year tree rings using accelerator mass spectrometry (AMS) with a statistical accuracy of -2.3 AMS 14C ages of the 36 viable samples are between 2708 and 2666 cal BP, a period in which the 14C of the IntCal04 curve (Reimer et al. 2004) shows an enhancement. The 14C ages of the samples are scattered with a Gaussian distribution around the interpolated IntCal04 calibration curve. The time profile of the deviations of the 36 14C ages from the interpolated IntCal04 calibration curve indicates a linear trend and a characteristic variability rather than a random fluctuation around the curve. The trend indicates a higher gradient than that of the interpolated IntCal04 calibration curve. The profile implies a periodic variation of approximately 11 yr and an amplitude of roughly 18 14C yr.
    • 14C Measurements of Tree Rings of a Japanese Cedar During 1945 to 2000 and Core Sampling for Environmental Studies

      Kawamura, H.; Kofuji, H.; Gasa, S.; Kamamoto, M.; Sawafuji, N.; Mori, M. (Department of Geosciences, The University of Arizona, 2007-01-01)
      Japanese cedar rings sampled from Aomori Prefecture, Japan, were measured to obtain tree-ring radiocarbon data covering a period of the latter half of the 20th century in the northernmost area of Honshu (mainland Japan), to obtain records of variation in atmospheric 14C concentration caused by past atmospheric nuclear testing, and to study any possible local effects. This work, carried out on a partial disk, was also intended to provide a reference for data obtained by core sampling of live, standing Japanese black pines as a part of marine environmental studies.
    • 14C-Dated Charcoal and Sediment Drilling Cores as First Evidence of Holocene Tsunamis at the Southern Spanish Coast

      Becker-Heidmann, Peter; Reicherter, Klaus; Silva, Pablo G. (Department of Geosciences, The University of Arizona, 2007-01-01)
      At 2 locations of the southern Spanish coast, we found indications for tsunamis induced by submarine earthquakes. Charcoal, which we sampled in 2 stratified, assumed tsunamigenic sediment (tsunamites) layers at the shore outside the ruins of the Roman city of Baelo Claudia, close to the Strait of Gibraltar (province of Cádiz), and radiocarbon dated, surprisingly turned out to be of identical age, about 465 BP. In the laguna of the Cabo de Gata (province of Almera), we found possible remnants of tsunamites in drilling cores deposited above organic sediments, 14C dated as 680 +/- 30 BP.
    • A Bayesian Framework for Age Modeling of Radiocarbon-Dated Peat Deposits: Case Studies from the Netherlands

      Blaauw, Maarten; Bakker, Ronald; Christen, J. Andrés; Hall, Valerie A.; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 2007-01-01)
      Recently, Bayesian statistical software has been developed for age-depth modeling (wiggle-match dating) of sequences of densely spaced radiocarbon dates from peat cores. The method is described in non-statistical terms, and is compared with an alternative method of chronological ordering of 14C dates. Case studies include the dating of the start of agriculture in the northeastern part of the Netherlands, and of a possible Hekla-3 tephra layer in the same country. We discuss future enhancements in Bayesian age modeling.
    • A Chronology of the Pre-Columbian Paracas and Nasca Cultures in South Peru Based on AMS 14C Dating

      Unkel, Ingmar; Kromer, Bernd; Reindel, Markus; Wacker, Lukas; Wagner, Günther (Department of Geosciences, The University of Arizona, 2007-01-01)
      The people of the Paracas and Nasca cultures, the creators of the famous geoglyphs, lived in the desert of the southern coast of Peru between about 800 BC and AD 650. The archaeological chronology of these cultures has been based almost exclusively on a sequence of ceramic styles. The absolute dating of some of the style phases was supported by a few radiocarbon dates (Rowe 1967). Here, we present an absolute chronology of the Paracas and Nasca cultures based on 14C dating of more than 100 organic samples from settlement and tomb relics, as well as on material derived from geoglyph sites in the Nasca/Palpa region (south Peru). The main focus has been on Nasca period settlement centers near Palpa, Los Molinos and La Mua, the Paracas period site of Jauranga, and the Initial period site of Pernil Alto. Most of the 14C samples were dated at the accelerator mass spectrometry (AMS) facility of the ETH Zurich (Switzerland). The targets were produced in the newly built graphitization line at the Heidelberg 14C laboratory (Germany). Clay (adobe) bricks, which are quite a common building material in Peru, were successfully tested to be used for AMS 14C dating of adobe architecture in Peruvian archaeology.
    • A Comparison of Radiocarbon and Archaeomagnetic Dating from an Archaeological Site in Spain

      Catanzariti, G.; McIntosh, G.; Osete, M. L.; Nakamura, T.; Rakowski, A. Z.; Ramírez González; Lanos, Ph. (Department of Geosciences, The University of Arizona, 2007-01-01)
      Reference archaeomagnetic secular variation (SV) curves recently have been proposed for the Iberian Peninsula and may now be used for archaeomagnetic dating. Archaeomagnetic dating is a relative dating technique that is strongly dependent on the age control of the data used to construct the reference curves. In order to test the method, an archaeological structure from central Spain has been studied. Samples have been taken for both archaeomagnetic and radiocarbon dating, and the results are compared. Close agreement is observed between both techniques, with the archaeomagnetic age of AD 603-999 overlapping the calibrated age of AD 770-890. These results demonstrate the reliability of the proposed reference curves as a dating tool within the Iberian Peninsula during this archaeological period.
    • A Cremated Bone Intercomparison Study

      Naysmith, Philip; Scott, E. Marian; Cook, Gordon T.; Heinemeier, Jan; van der Plicht, Johannes; Van Strydonck, Mark; Bronk Ramsey, Christopher; Grootes, Pieter M.; Freeman, Stewart T. (Department of Geosciences, The University of Arizona, 2007-01-01)
      It is now almost 10 yr since radiocarbon dating of cremated bone was first developed using the small carbonate component contained within the hydroxyapatite-based inorganic fraction. Currently, a significant number of 14C laboratories date cremated bone as part of their routine dating service. As a general investigation of cremated bone dating since this initial development, a small, cremated bone intercomparison study took place in 2005, involving 6 laboratories. Six cremated bone samples (including 2 sets of duplicates), with ages spanning approximately 15002800 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.
    • A Gas Ion Source for Radiocarbon Measurements at 200 kV

      Ruff, M.; Wacker, L.; Gäggeler, H. W.; Ter, M.; Synal, H.-A.; Szidat, S. (Department of Geosciences, The University of Arizona, 2007-01-01)
      The novel tabletop miniaturized radiocarbon dating system (MICADAS) at ETH Zurich features a hybrid Cs sputter negative ion source for the measurement of solid graphite and gaseous CO2 samples. The source produces stable currents of up to 6 A C out of gaseous samples with an efficiency of 36%. A gas feeding system has been set up that enables constant dosing of CO2 into the Cs sputter ion source and ensures stable measuring conditions. The system is based on a syringe in which CO2 gas is mixed with He and then pressed continuously into the ion source at a constant flow rate. Minimized volumes allow feeding samples of 330 g carbon quantitatively into the ion source. In order to test the performance of the system, several standards and blanks have successfully been measured. The ratios of 14C/12C could be repeated within statistical errors to better than 1.0% and the 13C/12C ratios to better than 0.2%. The blank was 1 pMC.
    • A Preliminary Determination of the Absolute 14C/12C Ratio of OX-I

      Roberts, M. L.; Southon, J. R. (Department of Geosciences, The University of Arizona, 2007-01-01)
      A preliminary determination of the absolute 14C/12C ratio of the oxalic acid I standard (NBS SRM 4990B) has been made. Using an accelerator mass spectrometry (AMS) system, a known number of radiocarbon ions were implanted in a thin copper foil. The foil was then combusted with the addition of 14C-free carrier material. This resulting gas (which had a known 14C/12C ratio) was graphitized and compared to OX-I material. This comparison yielded an absolute 14C/12C ratio of OX-I. The absolute 14C/12C ratio of OX-I, coupled with knowledge of the specific activity of OX-1, provides an alternative determination of the 14C half-life.
    • A Report on Phase 1 of the 5th International Radiocarbon Intercomparison (VIRI)

      Scott, E. Marian; Cook, Gordon T.; Naysmith, Philip; Bryant, Charlotte; O'Donnell, David (Department of Geosciences, The University of Arizona, 2007-01-01)
      The Fifth International Radiocarbon Intercomparison (VIRI) continues the tradition of the TIRI (third) and FIRI (fourth) intercomparisons (Scott 2003) and operates as an independent check on laboratory procedures in addition to any within-laboratory procedures for quality assurance. VIRI is a 4-yr project, with the first suite of samples (grain) sent out in September 2004 and the second suite (bone) sent out in December 2005. Further stages will include samples of peat, wood, and shell with a range of ages. The 4 grain samples included 2 samples (A and C) of barley mash (20 g for radiometric analysis and 2 mu-g for AMS), a grain (barley) byproduct from the manufacture of Glengoyne malt whiskey. The 2 remaining charred grain samples (B and D) were from excavations at Beth Saida and Tel Hadar, respectively (10 g for radiometric analysis and 4 seeds for AMS) and were provided by Elisabetta Boaretto of the Weizmann Institute. Consensus values for samples A and C are 109.2 (standard deviation [1 sigma] = 2.73) and 110.6 pMC (1 sigma = 2.48), and 2805 (1 sigma = 162.7) and 2835 BP (1 sigma = 190.8) for samples B and D, respectively. Sample A is a new sample that was collected in 2001, while sample C was used in the FIRI trial as samples G J (consensus value 110.7 pMC) and was collected in 1998. The expected ages (on archaeological grounds) of samples B and D are 2800 BP and 2850-2900 BP, respectively. The second suite of samples comprises bone, ranging in age from Medieval to close to background, and was distributed in December 2005. Samples for both radiometric and AMS laboratories include E: mammoth bone (>5 half-lives); F: horse bone (from Siberia, excavated in 2001); and H, I: whalebone. Finally, sample G (human bone) was only for AMS laboratories. Some of the issues related to using bone in a laboratory intercomparison will be discussed.
    • Accurate Lacustrine and Wetland Sediment Accumulation Rates Determined from 14C Activity of Bulk Sediment Fractions

      Walker, W. G.; Davidson, Gregg R.; Lange, Todd; Wren, Daniel (Department of Geosciences, The University of Arizona, 2007-01-01)
      In the absence of identifiable macrofossils in lacustrine sediments, radiocarbon dating must rely on pollen or bulk sediment fractions. Bulk sediment fractions are not generally preferred because they contain an unknown mixture of organic material of variable age, they may contain dead carbon such as lignite that is difficult to eliminate, and material of aquatic origin may be subject to reservoir effects. If the various processes that contribute carbon to the system are relatively constant over time, however, changes in 14C activity with depth may be used to accurately estimate sediment accumulation rates even if the absolute ages are erroneous. In this study, fine-grained fractions (250-710 m organic material, humic acids extracted from
    • AMS 14C Sample Preparation at the KCCAMS/UCI Facility: Status Report and Performance of Small Samples

      Santos, G. M.; Moore, R. B.; Southon, J. R.; Griffin, S.; Hinger, E.; Zhang, D. (Department of Geosciences, The University of Arizona, 2007-01-01)
      We present an overview of accelerator mass spectrometry (AMS) radiocarbon sample preparation and measurements, describing the technical upgrades that now allow us to routinely obtain 0.2-0.3% precision for 1-mg carbon samples. A precision of ~1% on samples with 100 g of carbon can also be achieved. We have also developed graphitization techniques and AMS procedures for ultra-small samples (down to 0.002 mg of carbon). Detailed time series are presented for large and small aliquots of standards such as NIST OX-I and OX-II; FIRI-C and -D; IAEA-C6, -C7 and -C8; and 14C-free samples.
    • An Information-Efficient Bayesian Model for AMS Data Analysis

      Palonen, V.; Tikkanen, P. (Department of Geosciences, The University of Arizona, 2007-01-01)
      A Bayesian model for accelerator mass spectrometry (AMS) data analysis is presented. Instrumental drift is modeled with a continuous autoregressive (CAR) process, and measurement uncertainties are taken to be Gaussian. All samples have a parameter describing their true value. The model adapts itself to different instrumental parameters based on the data, and yields the most probable true values for the unknown samples. The model is able to use the information in the measurements more efficiently. First, all measurements tell something about the overall instrument performance and possible drift. The overall machine uncertainty can be used to obtain realistic uncertainties even when the number of measurements per sample is small. Second, even the measurements of the unknown samples can be used to estimate the variations in the standard level, provided that the samples have been measured more than once. Third, the uncertainty of the standard level is known to be smaller nearer a standard. Fourth, even though individual measurements follow a Gaussian distribution, the end result may not. For simulated data, the new Bayesian method gives more accurate results and more realistic uncertainties than the conventional mean-based (MB) method. In some cases, the latter gives unrealistically small uncertainties. This can be due to the non-Gaussian nature of the final result, which results from combining few samples from a Gaussian distribution without knowing the underlying variance and from the normalization with an uncertain standard level. In addition, in some cases the standard error of the mean does not represent well the true error due to correlations within the measurements resulting from, for example, a changing trend. While the conventional method fails in these cases, the CAR model gives representative uncertainties.
    • Applying the Direct Absorption Method and LSC for 14C Concentration Measurement in Aqueous Samples

      Varlam, Carmen; Stefanescu, Ioan; Varlam, Mihai; Popescu, Irina; Faurescu, Ionut (Department of Geosciences, The University of Arizona, 2007-01-01)
      We investigated a simple, reliable radiocarbon measurement procedure for water samples using the direct absorption method for sample preparation, followed by low-level liquid scintillation spectrometry. This process has involved quantitative evaluation of the conversion steps in order to estimate the appropriate working parameters. The 14C activity of dissolved inorganic carbon (DIC) for several types of water (ranging from seawater to groundwater) has been measured, paying attention to the preparation requirements of each type of water. The main advantage of this method is the simplified sample preparation, allowing measurement of a great number of samples in less time. This method was designed for routine analysis of water samples, and it is proposed particularly for use in 14C monitoring programs of CANDU-type reactors.
    • Artemis, the New 14C AMS at LMC14 in Saclay, France

      Cottereau, E.; Arnold, M.; Moreau, C.; Baqué, D.; Bavay, D.; Caffy, I.; Comby, C.; Dumoulin, J-P.; Hain, S.; Perron, M.; et al. (Department of Geosciences, The University of Arizona, 2007-01-01)
      The new facility Artemis was installed in 2003 in Saclay, France. This 3MV NEC Pelletron is dedicated to high-precision radiocarbon measurements for French 14C laboratories. We will present information on Artemis along with our sample preparation methods. Results from measurements on some intercalibration samples will be given along with the values of measured blanks. Finally, we report on some problems we have encountered when measuring sputter cathodes with high CH outputs.
    • Author index

      Department of Geosciences, The University of Arizona, 2007-01-01
    • Background Components of a Liquid Scintillation Counter in the 14C Window

      Jonsson, G.; Theodórsson, P. (Department of Geosciences, The University of Arizona, 2007-01-01)
      We present a broad and detailed study of the background components of a liquid scintillation (LS) detector, using a simple laboratory-built system, ICELS. It was specifically designed for radiocarbon dating and is compact and easily transportable (total weight 35 kg). Its flexible LS detector unit has a dome-shaped vial with 3 mL benzene to which 45 mg butyl-PBD is added. The vial sits on the top of a vertical 28-mm-diameter phototube. The gamma radiation, to which the benzene is exposed under varying conditions, was measured by replacing the vial with a 38-mm-diameter NaI crystal. The pulse-height spectra of the 14C LS background and the NaI gamma background were measured in a surface laboratory and in a deep underground counting room with: 1) a lead shield of varying thickness; 2) lead of normal and low 210Pb concentration; 3) phototubes of 2 different types; and 4) varying benzene volume. The beta emission from the face of the tubes was measured with a low-level Geiger counter.
    • Carbon Isotopes in Tree Rings: Climate and the Suess Effect Interferences in the Last 400 Years

      Pazdur, Anna; Nakamura, Toshio; Pawełczyk, Sławomira; Pawlyta, Jacek; Piotrowska, Natalia; Rakowski, Andrzej; Sensuła, Barbara; Szczepanek, Małgorzata (Department of Geosciences, The University of Arizona, 2007-01-01)
      New records of delta-13C and ∆14C values in annual rings of pine and oak from different sites around the world were obtained with a time resolution of 1 yr. The results obtained for Europe (Poland), east Asia (Japan), and South America (Peru) are presented in this paper. The delta-13C and radiocarbon concentration of a-cellulose from annual tree rings of pine and of the latewood of oak were measured by both accelerator mass spectrometry (AMS) and liquid scintillation spectrometry (LSC). The values of 14S, which represent decreasing 14C concentrations caused by the emission of CO2 from fossil fuel use (Suess effect; Suess 1955), were calculated for each site. Low average 14S (about -0.4 to 0.8%) values for clean areas and high values (about 3.4-3.6%) for industrial and/or urbanized areas were noted. Records of the delta-13C values obtained for pine and oak from Poland were used to reconstruct climate changes during the last 400 yr. The results clearly indicate the climate cooling during the periods of the Maunder minimum (1645-1715) and the Dalton minimum (1790-1820). The anti-correlation between the delta-13C and ∆14C records during those 2 periods is clear if the 14C record is shifted toward older ages by 24 yr.
    • Charcoal Production During the Norse and Early Medieval Periods in Eyjafjallahreppur, Southern Iceland

      Church, M. J.; Dugmore, A. J.; Mairs, K. A.; Millard, A. R.; Cook, G. T.; Sveinbjarnardóttir, G.; Cough, P. A.; Roucoux, K. H. (Department of Geosciences, The University of Arizona, 2007-01-01)
      Timber procurement and the use of woodlands are key issues in understanding the open landscapes of the Norse and Medieval periods in the North Atlantic islands. This paper outlines evidence for the timing and mechanisms of woodland use and deforestation in an area of southern Iceland, which is tracked through the mapping and analysis of charcoal production pits. Precise dating of the use of these charcoal production pits within a Bayesian framework is demonstrated through the combination of tephrochronology, sediment accumulation rates, and multiple radiocarbon dates on the archaeological charcoal. Two phases of charcoal production and woodland exploitation have been demonstrated, the first within the first 2 centuries of settlement (cal AD 870-1050) and the second phase over 100 yr later (cal AD 1185-1295). The implications for using charcoal as a medium for 14C dating in Iceland and the wider North Atlantic are then explored. Archaeobotanical analysis of the charcoal sampled from the pits has indicated that birch roundwood was the dominant wood used, that the roundwood was stripped from larger shrubs/trees in late spring/early summer, and that certain sizes and ages of roundwood were harvested. Finally, the timing of the charcoal production is placed into the wider debate on deforestation across Iceland during the Norse and early Medieval periods.
    • Chronological and Dietary Aspects of the Human Burials from Ajdovska Cave, Slovenia

      Bonsall, C.; Horvat, M.; McSweeney, K.; Masson, M.; Higham, T. F. G.; Pickard, C.; Cook, G. T. (Department of Geosciences, The University of Arizona, 2007-01-01)
      Ajdovska Jama (The Pagans Cave) in southeast Slovenia lies within the catchment of the River Sava, a major tributary of the Danube. The site is well known for its Neolithic burials and has been excavated to a high standard on various occasions since 1884. The human remains at the site occurred as distinct clusters of mainly disarticulated bones belonging to at least 31 individuals. Hitherto, dating of the burials has been based on the associated archaeological finds, including a few low-precision radiometric radiocarbon measurements on charred plant material. In the present study, bones from 15 individuals were subsampled for accelerator mass spectrometry (AMS) and stable isotope analyses. These comprised adults and children from 3 of the clusters. The results of the study indicate that the burials all belong to a relatively short time interval, while the stable isotope data indicate a mixed diet based on C3 plant and animal food sources. These interpretations differ somewhat from those of previous researchers. The AMS 14C and stable isotope analyses form part of a wider investigation of dietary and demographic change from the Mesolithic to the Iron Age in the Danube Basin.