• Pre-Bomb Marine Reservoir Variability in the Kimberley Region, Western Australia

      O'Connor, Sue; Ulm, Sean; Fallon, Stewart J.; Barham, Anthony; Loch, Ian (Department of Geosciences, The University of Arizona, 2010-01-01)
      New Delta-R values are presented for 10 known-age shells from the Kimberley region of northwest Australia. Previous estimates of Delta-R for the Kimberley region are based on only 6 individual shell specimens with dates of live collection known only to within 50 yr (Bowman 1985a). Here, we describe the results of our recent attempts to constrain Delta-R variability for this region by dating a suite of known-age pre-AD 1950 shell samples from the Australian Museum and Museum Victoria. A regional Delta-R of 58 +/- 17 14C yr for open waters between Broome and Cape Leveque is recommended based on 7 of these specimens. The criteria used to select shells for dating and inclusion in the regional mean are discussed.
    • Simple Pretreatment Method Development for Iron and Calcium Carbonate Samples

      Park, Junghun; Hong, Wan; Choi, Han Woo; Kim, Joonkon; Kim, Gi Dong (Department of Geosciences, The University of Arizona, 2010-01-01)
      Since iron artifacts generally contain trace amounts of carbon, an iron sample needs to be relatively large, as compared to other materials, and a specially designed combustion system is required. An elemental analyzer (EA) was used for the combustion of iron without any special chemical treatment. CO2 gas with 1 mg of carbon was obtained from the combustion of an iron artifact by using an EA and reduced to graphite for accelerator mass spectrometry (AMS) measurement. In this work, AMS dating results done at the Korea Institute of Geoscience and Mineral Resources (KIGAM) for several ancient iron artifacts are presented and compared with independently estimated ages. This method was found to be useful for the pretreatment of iron artifacts that contained 0.1% carbon. A simple pretreatment method using an EA was also applied to calcium carbonate (CaCO3) samples. Samples were preheated overnight at 100-300 C, without any special chemical treatment. This removed modern CO2 contamination and the background level decreased to a comparable value measured in samples treated with phosphoric acid under vacuum.
    • Spatial Radiocarbon and Stable Carbon Isotope Variability of Mineral and Thermal Waters in Slovakia

      Povinec, P. P.; Franko, O.; Šivo, A.; Richtáriková, M.; Breier, R.; Aggarwal, P. K.; Araguás-Araguás, L. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Isotope hydrology investigations were carried out with the aim to study isotope variability in mineral and thermal waters (MTW) of Slovakia. The aquifers of MTW were formed by Triassic limestones and dolomites, which are found in the mountains as well as in the pre-Tertiary substratum of depressions and lowlands. The MTW were of artesian and/or open structures. At present, there are only boreholes available, as natural outflows have already been captured by them. Large spatial isotope variability (14C between 2 and 33.6 pMC, 18O between -11.8 and -9.8, and 13C between -12.7 and -3.4 for bicarbonates and -21 and -4.9 for free CO2) and heterogeneity of MTW was observed, indicating different origins of MTW. Corrected radiocarbon apparent ages of MTW indicate that they mostly infiltrated during the Würm and Holocene periods.
    • Radiocarbon Dating of the Last Volcanic Eruptions of Ciomadul Volcano, Southeast Carpathians, Eastern-Central Europe

      Harangi, Sz; Molnár, M.; Vinkler, A. P.; Kiss, B.; Jull, A. J. T.; Leonard, A. G. (Department of Geosciences, The University of Arizona, 2010-01-01)
      This paper provides new accelerator mass spectrometry (AMS) radiocarbon age data for the last volcanic events in the Carpathian-Pannonian region of eastern-central Europe. The eruption ages were determined on charcoal fragments collected from pumiceous pyroclastic flow deposits at 2 localities of the Ciomadul Volcano. Two charcoal samples from the southeastern margin of the volcano (Bixad locality) set the date of the last volcanic eruption to 27,200 +/- 260 yr BP (29,500 +/- 260 cal BC). On the other hand, our data show that the Tusnad pyroclastic flow deposit, previously considered as representing the youngest volcanic rock of the region, erupted at ~39,000 yr BP (~41,300 cal BC). Thus, a period of dormancy more than 10,000 yr long might have elapsed between the 2 volcanic events. The different ages of the Tusnad and Bixad pyroclastic flow deposits are confirmed also by the geochemical data. The bulk pumices, groundmass glass, and the composition of the main mineral phases (plagioclase and amphibole) suggest eruption of slightly different magmas. Considering also the assumed long volcanic history (~600 ka) of the Ciomadul, these data suggest that further detailed studies are necessary on this seemingly inactive volcano in order to evaluate the possible renewal of volcanic activity in the future.
    • Report on the 20th International Radiocarbon Conference Graphitization Workshop

      Turnbull, Jocelyn; Prior, Christine (Department of Geosciences, The University of Arizona, 2010-01-01)
      A sample preparation workshop was convened at the 20th International Radiocarbon conference, with about 30-40 attendees. The term "sample preparation" was not further specified to allow participants to address the laboratory issues most important to them. Given the short time available, the focus quickly narrowed to details of graphite preparation for accelerator mass spectrometry (AMS), with particular interest in procedures for small samples, and hence we have changed the title to reflect the focus. Here, we summarize the workshop discussion, adding additional background information and references to publications. Several aspects of graphite preparation are included: catalyst types and ratio of catalyst to carbon; optimal reaction temperatures for various sample sizes; methods for water removal; types of pressure transducers; preconditioning of catalyst; and problems with blank values in very small samples. The pros and cons of sample dilution were also discussed.
    • Robust Bayesian Analysis, an Attempt to Improve Bayesian Sequencing

      Weninger, Franz; Steier, Peter; Kutschera, Walter; Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2010-01-01)
      Bayesian sequencing of radiocarbon dates deals with the problem that in most cases there does not exist an unambiguous way to define the so-called prior function, which represents information in addition to the result of the 14C measurements alone. However, a random choice of a particular prior function can lead to biased results. In this paper, "robust Bayesian analysis," which uses a whole set of prior functions, is introduced as a more reliable method. The most important aspects of the mathematical foundation and of the practical realization of the method are described. As a general result, robust Bayesian analysis leads to higher accuracy, but paid for with reduced precision. Our investigations indicate that it seems possible to establish robust analysis for practical applications.
    • Studies on the Preparation of Small 14C Samples with an RGA and 13C-Enriched Material

      Liebl, Jakob; Avalos Ortiz, Roswitha; Golser, Robin; Handle, Florian; Kutschera, Walter; Steier, Peter; Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2010-01-01)
      The minimum size of radiocarbon samples for which reliable results can be obtained in an accelerator mass spectrometry (AMS) measurement is in many cases limited by carbon contamination introduced during sample preparation (i.e. all physical and chemical steps to which samples were subjected, starting from sampling). Efforts to reduce the sample size limit down to a few mu-g carbon require comprehensive systematic investigations to assess the amount of contamination and the process yields. We are introducing additional methods to speed up this process and to obtain more reliable results. A residual gas analyzer (RGA) is used to study combustion and graphitization reactions. We could optimize the reaction process at small CO2 pressures and identify detrimental side reactions. Knowing the composition of the residual gas in a graphitization process allows a reliable judgment on the completeness of the reaction. Further, we use isotopically enriched 13C (greater than or equal to 98% 13C) as a test material to determine contamination levels. This offers significant advantages: 1) The measurement of 12C/13C in CO2 is possible on-line with the RGA, which significantly reduces turnaround times compared to AMS measurements; 2) Both the reaction yield and the amount of contamination can be determined from a single test sample. The first applications of isotopically enriched 13C and the RGA have revealed that our prototype setup has room for improvements via better hardware; however, significant improvements of our sample processing procedures were achieved, eventually arriving at an overall contamination level of 0.12 to 0.15 mu-g C during sample preparation (i.e. freeze-drying, combustion, and graphitization) of mu-g-sized samples in aqueous solution, with above 50% yield.
    • Spatial Variation in the Marine Radiocarbon Reservoir Effect throughout the Scottish Post-Roman to Late Medieval Period: North Sea Values (500-1350 BP)

      Russell, N.; Cook, G. T.; Ascough, P. L.; Dugmore, A. J. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The marine radiocarbon reservoir effect (MRE) occurs as a spatially and temporally dependent variable owing to localized changes in oceanic water composition. This study investigates Delta-R values (deviations from the global average MRE whose Delta-R = 0) during the period 500-1350 BP for the east coast of Scotland, where a complex estuarine system exists that drains into the semi-enclosed North Sea basin. Due to the availability of suitable archaeological samples, the data set has a distinct Medieval focus that spans the area from Aberdeen in the north to East Lothian in the south. Many of the Delta-R values are not significantly different from 0 (the global average), but there are occasional excursions to negative values (max -172 +/- 20) indicating the presence of younger water. These values show greater variability compared to other published data for this general region, suggesting that considerable care must be taken when dating marine derived samples from archaeological sites on the east coast of Scotland.
    • A Comparison of Cellulose Extraction and ABA Pretreatment Methods for AMS 14C Dating of Ancient Wood

      Southon, J. R.; Magana, A. L. (Department of Geosciences, The University of Arizona, 2010-01-01)
      We have compared accelerator mass spectrometry (AMS) radiocarbon results on wood samples at or near the limit of 14C dating, pretreated with a standard acid-base-acid (ABA) protocol, with those obtained from cellulose prepared from the same samples by several modifications of the Jayme-Wise cellulose extraction method (Green 1963). These tests were carried out to determine the most efficient way to ensure low backgrounds in 14C measurements of well-preserved ancient wood samples.
    • A New Radiocarbon Pretreatment Method for Molluscan Shell Using Density Fractionation of Carbonates in Bromoform

      Russo, Christopher M.; Tripp, Jennifer A.; Douka, Katerina; Higham, Thomas F. G. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Coastal archaeological sites that lack organic remains for radiocarbon dating are often abundant sources of molluscan shells. As a substitute for materials such as bone and charcoal, shells can be analyzed with 14C dating to determine a site's age. Despite their being convenient, non-mobile archaeological artifacts, molluscan shells are plagued by several issues, including carbonate remodeling, in which aragonite in shells is converted to calcite as predicted by thermodynamics. We present here a carbonate density separation technique that addresses the issue of carbonate remodeling. Using a density fractionation with bromoform, aragonite concentrations are enriched in shells that have undergone significant remodeling. The technique has been applied to archaeological shells and has returned dates that are younger than those previously determined for the same shells.
    • Scandinavian Models: Radiocarbon Dates and the Origin and Spreading of Passage Graves in Sweden and Denmark

      Paulsson, Bettina Schulz (Department of Geosciences, The University of Arizona, 2010-01-01)
      Approximately 2700 radiocarbon results are currently available from European megalithic contexts. The interpretation of these 14C dates is often difficult. It is not easy to connect many of them from their archaeological context to the construction or the burial phase of the graves. This paper focuses on the megaliths of Scandinavia--a special megalith region--as it is the only place in Europe with 14C dates directly referable to the construction of the passage graves, the graves have good bone preservation, and new dating sequences are available. Some 188 14C results are now available from Scandinavian passage graves. In Sweden, new data suggest that these graves were built from the first half of the 35th century BC onwards. The 14C dates from birch bark as filling material between dry walls make it possible to build a sequence for the construction phase of the passage graves in Denmark from the 33rd century BC onward. With an interpretative Bayesian statistical framework, it is possible to untangle the nuances of the differences for the origin and the spreading of the megaliths in the different regions, to define, together with the archaeological remains, possible cultural-historical processes behind these phenomena and to discuss diffusion versus convergence.
    • Table of Contents

      Department of Geosciences, The University of Arizona, 2010-01-01
    • A Report on Phase 2 of the Fifth International Radiocarbon Intercomparison (VIRI)

      Scott, E. Marian; Cook, Gordon T.; Naysmith, Philip (Department of Geosciences, The University of Arizona, 2010-01-01)
      The Fifth International Radiocarbon Intercomparison (VIRI) continues the tradition of the TIRI (third) and FIRI (fourth) (Scott 2003) intercomparisons and operates in addition to any within-laboratory quality assurance measures as an independent check on laboratory procedures. VIRI is a phased intercomparison; results for the first phase, which employed grain samples, were reported in Scott et al. (2007). The second phase, involving bone samples, is reported here. The third and final phase, which includes samples of peat, wood, and shell, has also been completed and a companion paper appears in these proceedings. Five bone samples were made available and included Sample E: mammoth bone (>5 half-lives); Sample F: horse bone (from Siberia, excavated in 2001; and Samples H and I: whale bones (approximately 2 half-lives). Sample G (human bone) was accessible only to accelerator mass spectrometry (AMS) laboratories because of the limited amount of sample available. More than 40 laboratories participated in Phase 2 and consensus values for the ages were as follows: Sample E = 39,305 14C yr BP (standard deviation [1 sigma] = 121 yr); Sample F = 2513 yr BP (1 sigma = 5 yr); Sample G = 969 yr BP (1 sigma = 5 yr); Sample H = 9528 yr BP (1 sigma = 7 yr); and Sample I = 8331 yr BP (1 sigma = 6 yr). Sample G had previously been dated by 4 laboratories and a weighted mean of 934 +/- 12 yr BP had been quoted. Sample I had previously been dated at 8335 +/- 25 yr BP and Sample H had been dated at 9565 +/- 130 yr BP. Results for Sample H and Sample I are in good agreement with the previous results; Sample G results, however, give a value that is significantly older than the previously reported results.
    • A New Automated Extraction System for 14C Measurement for Atmospheric CO2

      Turnbull, Jocelyn C.; Lehman, Scott J.; Morgan, Stephen; Wolak, Chad (Department of Geosciences, The University of Arizona, 2010-01-01)
      The radiocarbon content of atmospheric CO2 (∆14CO2) has long been of interest to atmospheric and Earth system researchers. Recent improvements in 14C measurement precision and reduction in sample size requirements have now made it possible to measure ∆14CO2 within existing trace gas sampling networks, most notably as a method to quantify recently added fossil-fuel-derived CO2 in the atmosphere. At INSTAAR, in collaboration with NOAA/ESRL, ~600 atmospheric samples from around the globe are prepared each year, and that number is anticipated to grow in connection with various monitoring and data assimilation efforts. To accommodate the growing demand and reduce per sample costs, we developed an automated extraction system to quantitatively isolate CO2 from whole air for AMS 14C analysis. Twenty samples can be extracted in 1 fully automated run, taking 10-12 hr to complete and requiring only about 1 hr of operator time, a substantial improvement over the manual extraction system. CO2 is extracted cryogenically by flowing the whole air over a liquid nitrogen trap, after first removing water in a trap at -85 C. Large volume vacuum lines are used to extract ~30 mol of CO2 in less than 10 min, keeping contamination from leaks to a minimum and allowing rapid processing and greater throughput. 13C measurements on the resultant CO2 demonstrate that extraction is quantitative, and extractions of 14C-free air show that no significant modern contamination occurs. Replicate analyses of standard materials indicate that both mean values and precision are comparable to those for the manual extraction system.
    • A New Attempt to Establish the International Radiocarbon Soils Database (IRSDB)

      Becker-Heidmann, Peter; Heidmann, Pascal (Department of Geosciences, The University of Arizona, 2010-01-01)
      Twenty years after the first International Radiocarbon Database Workshop, and 13 yr after the setup of a preliminary structure for a worldwide database on 14C dates of soils, sound reasons and excuses for not establishing a real and globally accessible database have diminished. Climate change itself is widely accepted as reality now, and the strong demand of the modeling community for reliable data of the carbon pool--especially in soils--has been maintained. With the steadily increasing capacity of 14C dating facilities, these data can be and are produced. Nevertheless, they still cannot be accessed easily and equally enough. Now, decreased costs of hardware and recent developments of the internet enable the IRSDB to be implemented, in a joint effort. As a seed, a test server has been set up, with open-source software, housing the database in alpha-stage, a web interface, and a community portal. Thus, the development of the design as well as the data input of the database is done in close collaboration of the users of the database, the laboratories, soil scientists, archaeologists, modelers, other scientists, and interested laypersons. In order to guarantee the longtime independence of the availability and usability of the database from vendors or changing standards, only widely used open-source software and open standards are used. Therefore, the development of plug-ins for data input from laboratory databases or output to different required formats as well as interfaces to GIS and other software is possible. A version control system takes care of the integrity of the data.
    • A New 14C Data Set of the PY608W-PC Sediment Core from Lake Pumoyum Co (Southeastern Tibetan Plateau) over the Last 19 kyr

      Watanabe, Takahiro; Matsunaka, Tetsuya; Nakamura, Toshio; Nishimura, Mitsugu; Izutsu, Yasuhiro; Minami, Motoyasu; Nara, Fumiko Watanabe; Kakegawa, Takeshi; Zhu, Liping (Department of Geosciences, The University of Arizona, 2010-01-01)
      A new continuous sediment core (PY608W-PC; 3.8 m length) for reconstruction of climatic and environmental changes in the southeastern Tibetan Plateau was taken from the eastern part of Lake Pumoyum Co in August 2006. Sediment layers of the lower part of PY608W-PC (380-300 cm depth) were composed mainly of relatively large plant residues (up to ~3 cm in length) with an admixture of fine sand and sandy silt. The large plant residues disappeared at ~300-290 cm depth in core PY608W-PC and were replaced by silt-silty clay. The large plant residues from the lower part of PY608W-PC could be aquatic, because the plant residues were extremely enriched in 13C (up to -3.0‰, -5.6 +/- 2.3‰ on average). On the other hand, the plant residue concentrates (PRC fractions) from the upper part of the core (290-0 cm in depth) could be terrestrial C3 plants (delta-13C = -21.8 +/- 1.7 on average). Radiocarbon dating was performed on the large plant residues and PRC fractions from the PY608W-PC sediment core, which represented the chronology from ~19,000 cal BP to present.
    • Spatial Distribution of ∆14C Values of Organic Matter in Surface Sediments off Saru River in Northern Japan, One Year after a Flood Event in 2006

      Nagao, Seiya; Irino, Tomohisa; Aramaki, Takafumi; Ikehara, Ken; Katayama, Hajime; Otosaka, Shigeyoshi; Uchida, Masao; Shibata, Yasuyuki (Department of Geosciences, The University of Arizona, 2010-01-01)
      Dispersion and deposition of terrestrial organic matter by flooding on the inner shelf were studied using C/N ratios, 13C, and ∆14C values of sedimentary organic matter. Surface sediment samples (top 2 cm) were collected from coastal areas near the Saru River in southwestern Hokkaido, northern Japan, 1 yr after a flood event in 2006. Riverine suspended solids were also collected at a fixed station downstream during 2006-2008. Sandy sediments were located at the front of the river mouth and the western part of the sampling area, with the 13C of organic matter ranging from -23.8 to -22.0, ∆14C of -655 to -388, and an organic carbon/total nitrogen (C/N) ratio of 5.9-7.7. On the other hand, silt and clay sediments were distributed in a restricted area 11-16 km from the river mouth, with lighter 13C (-26.7 to -24.1) and higher ∆14C (-240 to -77) of organic matter and C/N ratio (7.8-13.3). From end-member analysis, the apparently younger and less degraded organic matter in the silt and clay sediments consists mainly of terrestrial organic matter released by flood events. They remain in the depression, although most flood deposits were moved to deep-sea environments.
    • 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.