• A Simplified In Situ Cosmogenic 14C Extraction System

      Pigati, Jeffrey S.; Lifton, Nathaniel A.; Jull, A. J. Timothy; Quade, Jay (Department of Geosciences, The University of Arizona, 2010-01-01)
      We describe the design, construction, and testing of a new, simplified in situ radiocarbon extraction system at the University of Arizona. Blank levels for the new system are low ((234 +- 11) x 10^3 atoms (1 sigma; n = 7)) and stable. The precision of a given measurement depends on the concentration of 14C, but is typically <5% for concentrations of 100 x 10^3 atoms g^(-1) or more. The new system is relatively small and easy to construct, costs significantly less than the original in situ 14C extraction system at Arizona, and lends itself to future automation.
    • A Thermal and Acid Treatment for Carbon Extraction from Cast Iron and Its Application to AMS Dating of Cast Iron Objects from Ancient Korea

      Park, J. S.; Burr, G. S.; Jull, A. J. T. (Department of Geosciences, The University of Arizona, 2010-01-01)
      A method of thermal and acid treatments was developed at the Archaeo-metallurgy Laboratory of Hongik University in Korea to extract carbon from cast iron, and carbon objects thus prepared from cast iron artifacts of ancient Korea were dated at the University of Arizona's AMS Facility. The thermal treatments consist of heating a specimen to ~1000 C in a controlled environment with reduced oxygen potential, then cooling it rapidly to room temperature. The heating causes the cementite phase in white cast iron to be graphitized and the quenching suppresses pearlite formation. The specimen then consists of flakes of graphite embedded in a matrix of martensite. The next stage of the treatment is to dissolve the martensite matrix in a solution of nitric and hydrochloric acids to release the graphite as a powder. This material is then cleaned, dried, and pressed into target holders for accelerator mass spectrometry (AMS) analysis. The method was applied to a collection of artifacts from the Korean Three Kingdoms period (about AD 300-668) and the AMS results were compared with chronological estimates from other means.
    • A Wiggle-Matched Date for the Copper Age Cemetery at Manerba del Garda, Northern Italy

      Barfield, Lawrence H.; Manning, Sturt W.; Valzolgher, Erio; Higham, Thomas F. G. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The cemetery in the Riparo Valtenesi rockshelter at Manerba del Garda in northern Italy is well known for its wooden burial chambers. These chambers are some of the best sources of evidence for 3rd millennium BC collective burial in Europe. To further refine the absolute dating of burial activity at the site (beyond the approximate data provided by a previous series of routine radiocarbon measurements), a charred construction oak timber was sampled from Chamber 133 for 14C dendro wiggle-matching (DWM). We present the results from the DWM analysis, the first of its kind for the Italian Copper Age as a whole, establishing a terminus post quem for construction of Chamber 133 ~2955-2872 cal BC.
    • Age and Growth Rate Dynamics of an Old African Baobab Determined by Radiocarbon Dating

      Patrut, A.; Mayne, D. H.; Vo, K. F.; Lowy, D. A.; Venter, S.; McNichol, A. P.; Roberts, M. L.; Margineanu, D. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In 2008, a large African baobab (Adansonia digitata L.) from Makulu Makete, South Africa, split vertically into 2 sections, revealing a large enclosed cavity. Several wood samples collected from the cavity were processed and radiocarbon dated by accelerator mass spectrometry (AMS) for determining the age and growth rate dynamics of the tree. The 14C date of the oldest sample was found to be of 1016 22 BP, which corresponds to a calibrated age of 1000 15 yr. Thus, the Makulu Makete tree, which eventually collapsed to the ground and died, becomes the second oldest African baobab dated accurately to at least 1000 yr. The conventional growth rate of the trunk, estimated by the radial increase, declined gradually over its life cycle. However, the growth rate expressed more adequately by the cross-sectional area increase and by the volume increase accelerated up to the age of 650 yr and remained almost constant over the past 450 yr.
    • Age-Depth Model of Lake Soppensee (Switzerland) Based on the High-Resolution 14C Chronology Compared with Varve Chronology

      Hajdas, Irka; Michczyński, Adam (Department of Geosciences, The University of Arizona, 2010-01-01)
      An age-depth model for laminated sediments of Lake Soppensee is constructed using radiocarbon ages of macrofossils and a depositional model of the OxCal v 4.1 program with the updated IntCal09 data set. The resulting calendar chronology is compared with the varve chronology that was built for this record in a previous study (Hajdas 1993); there is a very good agreement between the 2 approaches. This illustrates the potential of high-resolution 14C dating for construction of reliable, high-resolution calendar timescales for sedimentary records. Based on the age-depth model of this study, the Vasset/Killian tephra found in sediment of Soppensee dates to a calendar age of 9291-9412 cal BP (2-delta range) while the Lachersee tephra dates to 12,735-12,871 cal BP (2-delta range). Precise dating of the Late Glacial boundaries is possible with this chronology but requires more precise correlation between proxies and records than typically practiced.
    • Alternative Explanations for Anomalous 14C Ages on Human Skeletons Associated with the 612 BCE Destruction of Nineveh

      Taylor, R. E.; Beaumont, W. C.; Southon, J.; Stronach, D.; Pickworth, D. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Three factors--contamination, a dietary reservoir effect, and a regional ∆14C anomaly--are considered as possible contributing explanations for an almost 2-century offset between the historically documented age of 612 BCE and the calibrated ages of 9 14C determinations obtained on 3 human skeletons directly associated stratigraphically with an archaeologically--and historically--defined 612 BCE event at the ancient site of Nineveh in northern Mesopotamia (Iraq). We note that on the order of a 1% (~80 yr) offset caused by one or a combination of these 3 factors, or other as yet unidentified additional factor(s), would be sufficient to move the average measured 14C age of these bone samples within the major "warp" in the 14C timescale during the mid-1st millennium BCE. We provide what we believe to be sufficient evidence that contamination is not a major factor in the case of these bone samples. At this time, we lack appropriate data to determine with sufficient rigor the degree to which a dietary reservoir effect may be contributing to the offset. At present, a posited regional ∆14C anomaly does not appear to be supported on the basis of data from several other localities in the Near East of similar age. One purpose of presenting this data set is to solicit comparisons with 14C values obtained on samples from additional, historically well-documented, known-age archaeological contexts for this time period in this and adjacent regions.
    • Alternative Methods for Cellulose Preparation for AMS Measurement

      Němec, Mojmir; Wacker, Lukas; Hajdas, Irka; Gäggeler, Heinz (Department of Geosciences, The University of Arizona, 2010-01-01)
      The main methods applied to clean plant material for radiocarbon dating are not compound-specific and generally remove only the easily exchangeable components by an acid-base-acid sequence and additional optional steps like Soxhlet extraction to remove resins and oxidative bleaching with NaClO2. The products are normally clean enough for standard 14C measurement, but in some cases it is desirable to have pure cellulose, which remains unchanged and immobile over longer time ranges, better representing the original plant material. In this work, 2 more compound-specific but still simple methods were tested to separate the cellulose from wood. The viscose method is based on the xanthification process used in the textile industry, where the alkali-cellulose with CS2 forms a soluble cellulose xanthate, which is then extracted and cellulose is recovered. The second procedure is based on the wood/cellulose dissolution in ionic liquid 1-butyl-3-methylimidazolium chloride [BMIM]Cl, when the dissolved cellulose could be precipitated again by simply adding a water-acetone mixture. This process was recently reported, but still not used in sample preparation procedures for 14C dating.
    • AMS 14C Dating of Human Bones Using Sequential Pyrolysis and Combustion of Collagen

      Wang, Hong; Ambrose, Stanley H.; Hedman, Kristin M.; Emerson, Thomas E. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The Radiocarbon Dating Laboratory at the University of Illinois has been using the pyrolysis-combustion technique to separate pyrolysis-volatile (Py-V) or low molecular weight and pyrolysis-residue (Py-R) or high molecular weight compounds for 14C dating of organic remains since 2003. We have applied this method to human collagen dating to examine the 14C age difference between low and high molecular weight organic compounds. Results show that both fractions of late prehistoric period human bones from Illinois archaeological sites yield identical 14C dates but that Py-V or low molecular weight fractions of Archaic period human bones appear to be slightly contaminated. In this case, Py-V components or low molecular weight collagen fraction yield older 14C dates, which could result from contamination from old organic-rich sediments. The pyrolysis-combustion technique provides an economical alternative method to date bones that have not been satisfactorily dated using conventional purification techniques.
    • AMS Dating of Human Bone from Cova de la Pastora: New Evidence of Ritual Continuity in the Prehistory of Eastern Spain

      McClure, Sarah B.; García Puchol, Oreto; Ulleton, Brendan J. (Department of Geosciences, The University of Arizona, 2010-01-01)
      We present the results of 10 AMS radiocarbon dates for Cova de la Pastora (Alcoi, Alicante), a burial cave attributed to the Late Neolithic/Chalcolithic in eastern Spain. The direct dating of 10 human mandibles from Cova de la Pastora indicates that the cave was used as a burial place from the Late Neolithic/Chalcolithic to the Bronze Age. These dates reveal a continuity of ritual use not previously identified at the site. This case also serves to highlight the utility of revisiting historic excavations and museum collections with modern techniques to shed new light on the prehistoric human record.
    • AMS Radiocarbon Dates from Pleistocene and Holocene Mammals Housed in the New York State Museum, Albany, New York, USA

      Feranec, Robert S.; Kozlowski, Andrew L. (Department of Geosciences, The University of Arizona, 2010-01-01)
    • AMS Radiocarbon Dating of an Ancient Pottery Workshop in Hepu County, China

      Ruan, X.; Guan, Y.; Xiong, Z.; Wu, W.; Wang, H.; Jiang, S.; He, M.; Liu, K.; Terrassi, F.; Capano, M. (Department of Geosciences, The University of Arizona, 2010-01-01)
      An ancient pottery workshop belonging to the Han Dynasty was excavated in Caoxie village, Hepu County. Caoxie village is an important archaeological site in Hepu County, Beihai City, in south China's Guangxi Zhuang Autonomous Region. It is believed that Hepu County was the oldest departure point on the ancient maritime trading route during the Han Dynasty (206 BC to AD 220) due to the ideal natural geographical conditions and the existence of a large number of Han tombs. Radiocarbon measurements on wood and charcoal samples from the Caoxie village site were performed at the Peking University AMS facility (PKU-AMS), Beijing, and the Centre for Isotopic Research for Cultural and Environmental Heritage (CIRCE) at Naples Second University, Italy. Calibrated ages were obtained with code CALIB 5 (Stuiver and Reimer 1993). The results of these measurements are presented and the related chronology is discussed.
    • AMS Radiocarbon Dating of Holocene Tephra Layers on Ulleung Island, South Korea

      Toyota, Ayu; Tayasu, Ichiro; Fujimaki, Reiji; Kaneko, Nobuhiro; Uchida, Masao; Shibata, Yasuyuki; Hiura, Tsutom (Department of Geosciences, The University of Arizona, 2010-01-01)
      Ulleung Island, a large stratovolcano, is located in the western part of the Japan Sea (East Sea), 130 km off the eastern coast of the Korean Peninsula. The Ulleung-Oki (U-Oki) is a widely distributed tephra in and around the Japan Sea, and has an age of 10.7 cal ka BP obtained from the Lake Suigetsu data set (central Japan). Of the 7 tephra layers (U-7 to -1) on the island, the pumiceous U-4, U-3, and U-2 tephra layers are petrochemically and petrographically similar to the U-Oki tephra. To determine the eruption ages of 3 tephra layers on Ulleung Island, we conducted radiocarbon dating for 5 soil and 2 charcoal samples. Although the soil samples have the C/N ratios from 5 to 10, the obtained 14C dates are still consistent with the tephra stratigraphy of the island. The calibrated 14C dates for the U-4, U-3, and U-2 tephras are 11 cal ka BP, 8.3 or 9 cal ka BP, and 5.6 cal ka BP, respectively, indicating that the explosive eruptions occurred in the island with a time interval of 2000 to 3000 yr during the period of the early to middle Holocene. Based on our chronology, the U-4 tephra is most likely correlated with the U-Oki tephra.
    • An Alternate Method of Diluting Dissolved Organic Carbon Seawater Samples for 14C Analysis

      Griffin, Sheila; Beaupré, Steven R.; Druffel, Ellen R. M. (Department of Geosciences, The University of Arizona, 2010-01-01)
      We present a time-saving modification to the ultraviolet (UV) oxidation method for analyzing dissolved organic carbon (DOC) concentration, ∆14C, and 13C measurements in seawater and standard materials. A low background (~0.2 +/- 0.2 M) was reported for pre-irradiated Milli-Q (MQ) water that was used to dilute samples for DOC 14C analysis (Beaupr et al. 2007). We use MQ water without pre-irradiation (background ~0.9 0.2 M) to dilute the sample. This method is suitable for small-volume, high-concentration samples (mass of sample DOC overwhelms mass of MQ water DOC). An acceptable precision of ∆14C measurements (5-9) is maintained. This revised method reduces the preparation time for diluted DOC ∆14C samples from 2 days to 1 day.
    • Approaches to Estimating Marine Protein in Human Collagen for Radiocarbon Date Calibration

      Dewar, Genevieve; Pfeiffer, Susan (Department of Geosciences, The University of Arizona, 2010-01-01)
      Determining the appropriate approach to calibrating radiocarbon dates is challenging when unknown and variable fractions of the carbon sample are derived from terrestrial and marine systems. Uncalibrated dates from a large number of human skeletons from Western Cape and Southern Cape locales, South Africa (n = 187), can be used to explore alternate approaches to the marine carbon correction. The approach that estimates theoretically expected minimum and maximum values for marine carbon ("expected") is compared to the approach that estimates observed minimum and maximum values ("observed"). Two case studies are explored, wherein skeletons interred together have non-overlapping conventional 14C ages. The case from the Western Cape is explored through carbon isotope values; the case from the Southern Cape uses nitrogen isotope values. In both cases, the approach using observed endpoints yields better date calibration results. Analysis of the large sample shows that mean values for estimated dietary % Marine, as calculated using expected and observed protocols, are significantly different. We conclude that the observed protocol is preferred, and that improved measures of the local marine reservoir (∆R) are needed for this region.
    • Archaeological Radiocarbon Dates for Studying the Population History in Eastern Fennoscandia

      Oinonen, M.; Pesonen, P.; Tallavaara, M. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In this work, archaeological radiocarbon data gathered from eastern Fennoscandia have been scrutinized to discuss their suitability for studies of population history. The temporal distribution of the archaeological 14C dates has been analyzed against possible research priorities and sample material deterioration. An outstanding 'Stone Age' maximum has been observed in practically all the displayed temporal date distributions. The pattern remains the same throughout the history of 14C dating in Finland. Due to sample material differences, equal taphonomic corrections based on 14C-dated volcanic deposits cannot account for all the sample degradation effects; therefore, material-dependent correction procedures are suggested.
    • Are Compact AMS Facilities a Competitive Alternative to Larger Tandem Accelerators?

      Suter, M.; Müller, A. M.; Alfimov, V.; Christl, M.; Schulze-König, T.; Kubik, P. W.; Synal, H.-A.; Vockenhuber, C.; Wacker, L. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In the last decade, small and compact accelerator mass spectrometry (AMS) systems became available operating at terminal voltages of 1 MV and below. This new category of instruments has become competitive for radiocarbon detection to larger tandem accelerators and many of these instruments are successfully used for 14C dating or biomedical applications. The AMS group at ETH Zurich has demonstrated that small instruments can be built, which allow measurements also of other radionuclides such as 10Be, 26Al, 129I, and the actinides. 41Ca measurements can be performed with sufficient sensitivity for biomedical applications. A summary of recent developments made at the 500kV Pelletron in Zurich is given and its performance is compared with that of a commercial compact instrument from the company High Voltage Engineering Europe (HVEE) in Amersfoort, the Netherlands, operating at 1MV at CNA in Seville, Spain, as well as with that of larger AMS facilities. It turns out that the ion optics, stripper design, and the detection system are critical for the performance.
    • Assessing the Potential for Radiocarbon Dating the Scales of Australian Lungfish (Neoceratodus forsteri)

      James, Kelly M.; Fallon, Stewart J.; McDougall, Andrew; Espinoza, Tom; Broadfoot, Craig (Department of Geosciences, The University of Arizona, 2010-01-01)
      We present a novel application for radiocarbon dating by aging 4 scales from a single large adult lungfish (Neoceratodus forsteri) from the Burnett River, in Queensland, Australia. The relict fish species lack a solid crystalline otolith, which precludes the use of the otolith annuli as a reliable age indicator. Previous attempts to age lungfish using a number of techniques have had only limited success. We report on ages obtained from the dense lamellar bone of the scale, which were isolated from the organic layers that thicken and subsequently obscure the 14C signal. Using the characteristics of the bomb curve, 2 parameter von Bertanalffy growth functions were fit, providing an estimate of absolute age to be ~65-70 yr. The information gleaned from this study will aid in assessing the population structure, and therefore management, of this vulnerable species.
    • Atmospheric Fossil Fuel CO2 Measurement Using a Field Unit in a Central European City during the Winter of 2008/09

      Molnár, M.; Haszpra, L.; Svingor, É.; Major, I.; Svetlik, I. (Department of Geosciences, The University of Arizona, 2010-01-01)
      A high-precision atmospheric CO2 monitoring station was developed as a field unit. Within this, an integrating CO2 sampling system was applied to collect samples for radiocarbon measurements. One sampler was installed in the second largest city of Hungary (Debrecen station) and 2 independent 14CO2 sampling lines were installed ~300 km from Debrecen in a rural site at Hegyhtsl station as independent background references, where high-precision atmospheric CO2 mixing ratios have been measured since 1994. Fossil fuel CO2 content in the air of the large Hungarian city of Debrecen was determined during the winter of 2008 using both the measurements of CO2 mixing ratio and 14C content of air. Fossil fuel CO2 was significantly enhanced at Debrecen relative to the clean-air site at Hegyhtsl.
    • Author Index

      Department of Geosciences, The University of Arizona, 2010-01-01
    • Blank Assessment for Ultra-Small Radiocarbon Samples: Chemical Extraction and Separation Versus AMS

      Santos, Guaciara M.; Southon, John R.; Drenzek, Nicholas J.; Ziolkowski, Lori A.; Druffel, Ellen; Xu, Xiaomei; Zhang, Dachun; Trumbore, Susan; Eglinton, Timothy I.; Hughen, Konrad A. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The Keck Carbon Cycle AMS facility at the University of California, Irvine (KCCAMS/UCI) has developed protocols for analyzing radiocarbon in samples as small as ~0.001 mg of carbon (C). Mass-balance background corrections for modern and 14C-dead carbon contamination (MC and DC, respectively) can be assessed by measuring 14C-free and modern standards, respectively, using the same sample processing techniques that are applied to unknown samples. This approach can be validated by measuring secondary standards of similar size and 14C composition to the unknown samples. Ordinary sample processing (such as ABA or leaching pretreatment, combustion/graphitization, and handling) introduces MC contamination of ~0.6 +/- 0.3 g C, while DC is ~0.3 +/- 0.15 g C. Today, the laboratory routinely analyzes graphite samples as small as 0.015 mg C for external submissions and =0.001 mg C for internal research activities with a precision of ~1% for ~0.010 mg C. However, when analyzing ultra-small samples isolated by a series of complex chemical and chromatographic methods (such as individual compounds), integrated procedural blanks may be far larger and more variable than those associated with combustion/graphitization alone. In some instances, the mass ratio of these blanks to the compounds of interest may be so high that the reported 14C results are meaningless. Thus, the abundance and variability of both MC and DC contamination encountered during ultra-small sample analysis must be carefully and thoroughly evaluated. Four case studies are presented to illustrate how extraction chemistry blanks are determined.