• 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.
    • Author Index

      Department of Geosciences, The University of Arizona, 2010-01-01
    • 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.
    • Timing of the Landslide-Dammed Lake Triggered by Earthquake, at Toyama River, Central Japan

      Goto, Akiko S.; Muramatsu, Takeshi; Teraoka, Yoshiji (Department of Geosciences, The University of Arizona, 2010-01-01)
      Huge landslides triggered by strong earthquakes or torrential rains can result in unstable natural dams that pose serious risks to humans. In this study, we attempt to document the age of an ancient earthquake that produced a landslide-dammed lake. A buried forest found in the Toyama River area of the southern Nagano Prefecture, central Japan, provides evidence of this event. The dammed lake formation has been previously estimated to have occurred in AD 714. However, the age of the dam and the way it was formed have never been directly determined. To determine the position and timing of the landslide dam, we analyzed the radiocarbon content of branches and wood fragments from a brecciated deposit. We show that the 14C dating method is suitable for clarifying the timing of burial for a variety of trees, although the method does not produce a narrow age for the event. In addition to the dating, we determined the landslide dam's position and reconstructed the formation of the lake.
    • Developments in the Calibration and Modeling of Radiocarbon Dates

      Ramsey, Christopher Bronk; Dee, Michael; Lee, Sharen; Nakagawa, Takeshi; Staff, Richard A. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Calibration is a core element of radiocarbon dating and is undergoing rapid development on a number of different fronts. This is most obvious in the area of 14C archives suitable for calibration purposes, which are now demonstrating much greater coherence over the earlier age range of the technique. Of particular significance to this end is the development of purely terrestrial archives such as those from the Lake Suigetsu sedimentary profile and Kauri tree rings from New Zealand, in addition to the groundwater records from speleothems. Equally important, however, is the development of statistical tools that can be used with, and help develop, such calibration data. In the context of sedimentary deposition, age-depth modeling provides a very useful way to analyze series of measurements from cores, with or without the presence of additional varve information. New methods are under development, making use of model averaging, that generate more robust age models. In addition, all calibration requires a coherent approach to outliers, for both single samples and where entire data sets might be offset relative to the calibration curve. This paper looks at current developments in these areas.
    • Editorial Board

      Department of Geosciences, The University of Arizona, 2010-01-01
    • Effects of Vegetation Switch and Subsequent Change in Soil Invertebrate Composition on Soil Carbon Accumulation Patterns, Revealed by Radiocarbon Concentrations

      Toyota, Ayu; Tayasu, Ichiro; Fujimaki, Reiji; Kaneko, Nobuhiro; Uchida, Masao; Shibata, Yasuyuki; Hiura, Tsutom (Department of Geosciences, The University of Arizona, 2010-01-01)
      Vegetation types strongly affect soil organic carbon (SOC) accumulation in the terrestrial ecosystem through multiple factors such as litter quality and soil biodiversity. However, the roles of soil fauna in SOC accumulation remain unclear. The objectives of this study were to (1) examine how changes in litter types and soil animal communities affect SOC accumulation in continuously forested or vegetation-switched forest areas; and (2) discuss the role of soil animals in SOC accumulation in forest ecosystems. We focused on soils that have accumulated on top of a volcanic ash layer in the 268 yr since a volcanic eruption in 1739. The radiocarbon "bomb spike" in the late 1950s and early 1960s provides a unique isotopic signature of soil carbon age. We investigated the combined effects of litter quality and soil invertebrate function on soil 14C accumulation patterns. To determine the effects of vegetation types on SOC accumulation, we selected 4 types of cool temperate forests, 2 of which had undergone a vegetation switch in about 1960 (conifer to broadleaved forest, CB; broadleaved forest to conifer, BC), and 2 that had continuous forests (conifer forest, CC; broadleaved forest, BB). The ∆14C values at depth intervals in CC were consistent with the expected bomb-14C profile. In contrast, ∆14C patterns in BB, BC, and CB differed from that of CC. Compared to CC, ∆14C values of the other sites showed relatively high 14C concentrations even in deeper soil layers, which suggests the bomb-induced 14C has been transported to a greater depth by soil animals. Current broadleaved forests (BB and CB) had higher biomass of litter-feeding invertebrates than in current coniferous forests (CC and BC). These results suggest that carbon from leaf litter was vertically translocated to deeper soil layers by the abundant soil invertebrates in broad-leaved forests. Disagreement with the expected soil profile in BC suggests that past vegetation (broadleaved forest) has affected the present SOC accumulation pattern.
    • Development of Graphitization of μg-Sized Samples at Lund University

      Genberg, J.; Stenström, K.; Elfman, M.; Olsson, M. (Department of Geosciences, The University of Arizona, 2010-01-01)
      To be able to successfully measure radiocarbon with accelerator mass spectrometry (AMS) in atmospheric aerosol samples, graphitization of small sample sizes ( 50 g carbon) must provide reproducible results. At Lund University, a graphitization line optimized for small samples has been constructed. Attention has been given to minimize the reduction reactor volume and each reactor is equipped with a very small pressure transducer that enables constant monitoring of the reaction. Samples as small as 25 g of carbon have been successfully analyzed, and the mass detection limit of the system has probably not been reached.
    • Wiggle-Match Dating of Wooden Samples from Iron Age Sites in Northern Italy

      Quarta, G.; Pezzo, M. I.; Marconi, S.; Tecchiati, U.; D'Elia, M.; Calcagnile, L. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Archaeological excavations carried out at the sites of Laion/Lajen (Bolzano/Bozen) and Stufles-Oberegger (Bressanone/Brixen) in northern Italy uncovered well-preserved wooden samples in cultural layers archaeologically dated to the Iron Age. From the 2 sites, different wooden samples were recovered that were well preserved enough to allow clear identification of the tree species and of the ring structure. Among the different wooden samples, 2 were selected for radiocarbon analyses: from Laion/Lajen, a beam with an unbroken sequence of 158 rings; from Stufles-Oberegger, a combusted trunk with a sequence of 217 rings. Both samples were identified as Larix decidua species. From each sequence, single rings were selected and submitted for accelerator mass spectrometry (AMS) 14C dating analysis at CEDAD. Conventional 14C ages were then calibrated to calendar ages using the IntCal04 atmospheric data set, while the statistical constraints resulting from the defined ring sequence were used to develop a wiggle-matching approach by making use of the Bayesian analysis functions available in OxCal. The obtained results are an important contribution in refining the chronology of the studied sites.
    • Comparison of 14C Ages between LSC and AMS Measurements of Choukai Jindai Cedar Tree Rings at 2600 cal BP

      Takahashi, Yui; Sakurai, Hirohisa; Suzuki, Kayo; Sato, Taiichi; Gunji, Shuichi; Tokanai, Fuyuki; Matsuzaki, Hiroyuki; Sunohara, Yoko (Department of Geosciences, The University of Arizona, 2010-01-01)
      Radiocarbon ages of Choukai Jindai cedar tree rings growing in the excess era of 14C concentrations during 2757-2437 cal BP were measured using 2 types of 14C measurement methods, i.e. liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS). The difference between the 2 methods is 3.7 +/- 5.2 14C yr on average for 61 single-year tree rings, indicating good agreement between the methods. The Choukai data sets show a small sharp bump with an average 14C age of 2497.1 +/- 3.0 14C yr BP during 2650-2600 cal BP. Although the profile of the Choukai LSC data set compares well with that of IntCal04, having a 14C age difference of 4.6 +/- 5.3 14C yr on average, the Choukai LSC 14C ages indicate variability against the smoothed profile of IntCal04.
    • Tree-Ring Dating and AMS Wiggle-Matching of Wooden Statues at Neunggasa Temple in South Korea

      Park, Won-Kyu; Kim, Yojung; Jeong, Ah-Reum; Kim, Sang-Kyu; Oh, Jung-Ae; Park, Suh-Young; Cho, Sunil; Park, Gyujun; Seo, Jeong-Wook (Department of Geosciences, The University of Arizona, 2010-01-01)
      This paper reports the results of tree-ring dating and accelerator mass spectrometry (AMS) wiggle-matching for wooden Buddhist statues stored at the Eungjindang Hall of Neunggasa Temple, South Korea. Among 23 statues, 10 were successfully dated by tree rings. The cutting date of logs used for the statues was determined as some time between late fall 1684 and early spring 1685 when the bark ring (AD 1684) completed latewood formation. The 95.4% confidence interval of a radiocarbon date (cal AD 1688-1713, 2 ), which was obtained by wiggle-matching 7 samples of a statue, is similar to the dendro-date (AD 1684). A historical document recorded that the statues in the Eungjindang of Neunggasa were dedicated in July 1685. The dendro-date and written record indicate that Eungjindang statues were made within 3-8 months after log cutting. This seems rather short if we consider the period required for natural drying to avoid defects such as cracking and crooking.
    • Variability of Dissolved Inorganic Radiocarbon at a Surface Site in the Northeast Pacific Ocean

      Druffel, Ellen R. M.; Beaupré, Steven; Griffin, Sheila; Hwang, Jeomshik (Department of Geosciences, The University of Arizona, 2010-01-01)
      We report radiocarbon measurements of dissolved inorganic carbon (DIC) in surface water samples collected daily during 12 cruises to Station M in the northeast Pacific off central California. Individual surface ∆14C values ranged from 22 to 70 over 10 yr. Variability of average cruise values is highest during winter likely due to increased mixing. A general decrease of ∆14C values was observed at a rate of about 3 per year between 1994 and 2004, about half of that in atmospheric CO2 during this period (Levin and Kromer 2004). The ∆14C results ranged from 2-18 during individual cruises and were often significantly larger than the total uncertainty for individual measurements (3.9). This indicates that a single ∆14C result from a surface site is not sufficient to capture the true variability of ∆14C in the surface ocean.
    • Comparison of Depth Profiles of 129I and 14C Concentration in the Surface Layer of Soils Collected from Northeastern Japan

      Matsuzaki, Hiroyuki; Tsuchiya, Yoko Sunohara; Muramatsu, Yasuyuki; Maejima, Yuji; Miyairi, Yosuke; Kato, Kazuhiro (Department of Geosciences, The University of Arizona, 2010-01-01)
      129I/127I and 14C/12C depth profiles were compared for the surface 30-cm layer of soil samples (Andisols) collected from Shimokita Peninsula, northeastern Japan, in November 2005. The 129I/127I and 14C/12C profiles have a clear correlation, even taking into account that the data include samples collected from different sites with different surface histories. These results, and considering that 14C/12C can be regarded as a proxy of the original depth in stable soil, show the diversity of the 129I/127I ratio at the surface among the sites, indicating variations in the thicknesses of the layers recently removed. At one of the sampling sites (P003-1), the ∆14C value measures ~110 near the surface, which is indicative of anthropogenic 14C produced by atmospheric testing of nuclear weapons during the late 1950s and early 1960s. This site has experienced no disturbances for at least the past 50 yr. The relatively high activity of 129I (0.8 mBq/kg) and the 129I/127I ratio (7 x 10^(-9)) observed at the top layer of this site can be considered a 'representative value' when considering the anthropogenic iodine transfer from the atmosphere to the ground. The observations also support 2 separate modes of 129I migration in the soil: i.e. "topmost quick diffusion" and "subsurface relatively slow migration process." Even in the "subsurface relatively slow migration zone," the 129I/127I ratio was still orders higher than the pre-anthropogenic natural level.
    • Compound-Specific Radiocarbon Analyses of Phospholipid Fatty Acids and n-Alkanes in Ocean Sediments

      Druffel, Ellen R. M.; Zhang, Dachun; Xu, Xiaomei; Ziolkowski, Lori A.; Southon, John R.; Dos Santos, Guaciara M.; Trumbore, Susan E. (Department of Geosciences, The University of Arizona, 2010-01-01)
      We report compound-specific radiocarbon analyses of organic matter in ocean sediments from the northeast Pacific Ocean. Chemical extractions and a preparative capillary gas chromatograph (PCGC) were used to isolate phospholipid fatty acids (PLFA) and n-alkanes from 3 cores collected off the coast of California, USA. Mass of samples for accelerator mass spectrometry (AMS) 14C analysis ranged from 13-100 g C. PLFA extracted from anaerobic sediments in the Santa Barbara Basin (595 m depth) had modern ∆14C values (-20 to +54), indicating bacterial utilization of surface-produced, post-bomb organic matter. Lower ∆14C values were obtained for n-alkanes and PLFA from coast (92 m depth) and continental slope (1866 m) sediments, which reflect sources of old organic matter and bioturbation. We present a brief analysis of the blank carbon introduced to samples during chemical processing and PCGC isolation.
    • 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.
    • Establishment of Chemical Preparation Methods and Development of an Automated Reduction System for AMS Sample Preparation at KIGAM

      Hong, Wan; Park, Jung Hun; Kim, Kyeong J.; Woo, Hyung Joo; Kim, Jun Kon; Choi, Han Woo; Kim, Gi Dong (Department of Geosciences, The University of Arizona, 2010-01-01)
      Many previous studies on the sample preparation of various kinds of radiocarbon dating samples by accelerator mass spectrometry (AMS) have been examined at KIGAM (Korea Institute of Geoscience and Mineral Resources) and our own procedures have been established. Furthermore, an automated reduction system has been developed. The volume of the reduction region was minimized to improve the reduction yield, and air-actuated pneumatic valves and solenoid arrays were used for computer control of the system. Operation of all the valves and vacuum pumps and signals from the temperature sensors and pressure gauges were interfaced to a personal computer with an A/D board. A computer program was also developed to perform automatic operation of the reduction system. This system consistently shows a higher reduction yield than 90%. The reduction time of the system is currently 140 min.
    • Extraction of In Situ Cosmogenic 14C from Olivine

      Pigati, Jeffrey S.; Lifton, Nathaniel A.; Jull, A. J. Timothy; Quade, Jay (Department of Geosciences, The University of Arizona, 2010-01-01)
      Chemical pretreatment and extraction techniques have been developed previously to extract in situ cosmogenic radiocarbon (in situ 14C) from quartz and carbonate. These minerals can be found in most environments on Earth, but are usually absent from mafic terrains. To fill this gap, we conducted numerous experiments aimed at extracting in situ 14C from olivine ((Fe,Mg)2SiO4). We were able to extract a stable and reproducible in situ 14C component from olivine using stepped heating and a lithium metaborate (LiBO2) flux, following treatment with dilute HNO3 over a variety of experimental conditions. However, measured concentrations for samples from the Tabernacle Hill basalt flow (17.3 +/- 0.3 ka4) in central Utah and the McCarty's basalt flow (3.0 +/- 0.2 ka) in western New Mexico were significantly lower than expected based on exposure of olivine in our samples to cosmic rays at each site. The source of the discrepancy is not clear. We speculate that in situ 14C atoms may not have been released from Mg-rich crystal lattices (the olivine composition at both sites was ~Fo65Fa35). Alternatively, a portion of the 14C atoms released from the olivine grains may have become trapped in synthetic spinel-like minerals that were created in the olivine-flux mixture during the extraction process, or were simply retained in the mixture itself. Regardless, the magnitude of the discrepancy appears to be inversely proportional to the Fe/(Fe+Mg) ratio of the olivine separates. If we apply a simple correction factor based on the chemical composition of the separates, then corrected in situ 14C concentrations are similar to theoretical values at both sites. At this time, we do not know if this agreement is fortuitous or real. Future research should include measurement of in situ 14C concentrations in olivine from known-age basalt flows with different chemical compositions (i.e. more Fe-rich) to determine if this correction is robust for all olivine-bearing rocks.
    • Experiences of Production and Homogeneity Analysis of an AMS 14C Sucrose Standard for High-Activity Measurements

      Sydoff, Marie; Stenström, Kristina (Department of Geosciences, The University of Arizona, 2010-01-01)
      Accurate accelerator mass spectrometry (AMS) measurements rely on standards with well-known isotopic ratios. For radiocarbon measurements, a number of standards with different properties are commercially available, of which the IAEA-C6 sucrose standard with a 14C value of 150.61 pMC is the most active. When analyzing biological samples resulting from studies using 14C-labeled substances, the activity content can be up to 100 times this value. Thus, there is a need for a standard material with higher activity content than IAEA-C6 for making accurate AMS measurements on this type of sample. This paper describes the attempts of producing a standard with an activity content of about 10 times modern carbon. The material chosen has to be chemically inert, preferably non-toxic, commercially available in 14C-labeled form, and the activity must be homogeneously distributed within the material. Two different standard materials were considered: urea and sucrose. Sucrose was chosen for the new standard, since it is non-toxic, inexpensive, and organic and on combustion, forms only carbon dioxide (CO2) and water (H2O). In this paper, we discuss our experience in the production and homogeneity analysis of this material, from the crystallization of the sucrose solution to the graphitization of the samples. When using an online combustion method and a septa-sealed vial reduction method, the AMS measurements indicated that the activity was not homogeneously distributed throughout the material. Contrary to this, measurements of the sucrose solution prior to recrystallization indicated that the activity was more homogeneously distributed before than after the recrystallization. In order to determine whether the inhomogeneity depended on the graphitization method (i.e. the combustion or the reduction method) or on the material itself, 3 different graphitization methods and 2 different methods of recrystallization were tested.