• 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 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.
    • 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 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 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.
    • 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 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-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 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 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.
    • 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.
    • 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.
    • Buried Ancient Forest and Implications for Paleoclimate since the Mid-Holocene in South China

      Shen, C. D.; Ding, P.; Wang, N.; Yi, W. X.; Ding, X. F.; Fu, D. P.; Liu, K. X.; Zhou, L. P. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The historical evolution of an ancient forest that developed at Gaoyao, south China, can be divided into 4 stages of radiocarbon intervals (1.1-1.5, 2.0-3.5, 3.6-4.0, and 4.3-4.9 ka) in which the last 3 stages all developed in a wetland and formed humic layers of 2.0, 0.5, and 0.7 m depth, respectively. The humic layers were interrupted by 2 white-gray silty clay layers that most likely formed during climate fluctuations. Four drought events were identified during the evolution of the ancient forest, occurring around 4.3, 3.6, 2.0, and 1.1 ka, respectively, with durations of ~1000 14C yr. These events are consistent with other records both in low- and high-latitude areas, in particular with the little ice ages occurring since the mid-Holocene. Precipitation likely increased from 5.0 to 3.6 ka in south China, then decreased, which is probably the main cause for the development as well as the demise of the ancient forest.
    • Centuries of Marine Radiocarbon Reservoir Age Variation within Archaeological Mesodesma donacium Shells from Southern Peru

      Jones, Kevin B.; Hodgins, Gregory W. L.; Etayo-Cadavid, Miguel F.; Andrus, C. Fred T.; Sandweiss, Daniel H. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Mollusk shells provide brief (5 yr per shell) records of past marine conditions, including marine radiocarbon reservoir age (R) and upwelling. We report 21 14C ages and R calculations on small (~2 mg) samples from 2 Mesodesma donacium (surf clam) shells. These shells were excavated from a semi-subterranean house floor stratum 14C dated to 7625 +/- 35 BP at site QJ-280, Quebrada Jaguay, southern Peru. The ranges in marine 14C ages (and thus R) from the 2 shells are 530 and 170 14C yr; R from individual aragonite samples spans 130 +/- 60 to 730 +/- 170 14C yr. This intrashell 14C variability suggests that 14C dating of small (time-slice much less than 1 yr) marine samples from a variable-R (i.e. variable-upwelling) environment may introduce centuries of chronometric uncertainty.
    • Characterization and Dating of Saline Groundwater in the Dead Sea Area

      Avrahamov, Naama; Yechieli, Yoseph; Lazar, Boaz; Lewenberg, Omer; Boaretto, Elisabetta; Sivan, Orit (Department of Geosciences, The University of Arizona, 2010-01-01)
      This work presents an attempt to date brines and determine flow rates of hypersaline groundwater in the extremely dynamic system of the Dead Sea (DS), whose level has dropped in the last 30 yr by ~20 m. The processes that affect the carbon species and isotopes of the groundwater in the DS area were quantified in order to estimate their flow rate based on radiocarbon and tritium methods. In contrast to the conservative behavior of most ions in the groundwater, the carbon system parameters indicate additional processes. The dissolved inorganic carbon (DIC) content of most saline groundwater is close to that of the DS, but its stable isotopic composition (13CDIC) is much lower. The chemical composition and carbon isotope mass balance suggest that the low 13CDIC of the saline groundwater is a result of anaerobic organic matter oxidation by bacterial sulfate reduction (BSR) and methane oxidation. The radiocarbon content (14CDIC) of the saline groundwater ranged from 86 pMC (greater than the ~82 pMC value of the DS in the 2000s) to as low as 14 pMC. The similarity between the 14CDIC value and Na/Cl ratio of the groundwater at the DS shore and that of the 1980s DS brine indicates that the DS penetrated to the aquifer at that time. The low 14CDIC values in some of the saline groundwater suggest the existence of ancient brine in the subaquifer.