• A Novel Approach for Developing High-Resolution Sub-Fossil Peat Chronologies with 14C Dating

      Donders, T. H.; Wagner, F.; Van der Borg, K.; De Jong, A. F. M.; Visscher, H. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Sub-fossil sections from a Florida wetland were accelerator mass spectrometry (AMS) dated and the sedimentological conditions were determined. 14C data were calibrated using a combined wiggle-match and 14C bomb-pulse approach. Repeatable results were obtained providing accurate peat chronologies for the last 130 calendar yr. Assessment of the different errors involved led to age models with 3-5 yr precision. This allows direct calibration of paleoenvironmental proxies with meteorological data. The time frame in which 14C dating is commonly applied can possibly be extended to include the 20th century.
    • A Puzzling Body from the River Thames in London

      Bayliss, Alex; Marshall, Peter; Sidell, Jane (Department of Geosciences, The University of Arizona, 2004-01-01)
      Radiocarbon measurements on a partially articulated female human skeleton, recovered from the foreshore of the river Thames in London, raised interesting questions of interpretation when the body did not produce the anticipated Neolithic date. A relatively recent 14C age and a strong marine component to the individuals diet, identified by stable isotope measurements, means that the date of death is difficult to estimate accurately, although the body probably does not constitute a forensic case.
    • A Pretreatment Procedure for the AMS Radiocarbon Dating of Sub-Fossil Insect Remains

      Tripp, J. A.; Higham, T. F. G.; Hedges, R. E. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Two pretreatment methods for accelerator mass spectrometry (AMS) dating of insect remains were explored. One method involves a simple acid wash that removes carbonate, while the other is based on the industrial purification of chitin and results in isolation of polymeric chitosan. No contamination is observed from Maillard reactions during the deacetylation reaction used to isolate the chitosan. The methods were tested on Coleoptera samples from two Roman Britain sites. Our results demonstrate that both methods produce acceptable AMS dates that correspond well to the expected age of the deposits from which they came.
    • A Review of the Evidence for Extinction Chronologies for Five Species of Upper Pleistocene Megafauna in Siberia

      Orlova, Lyobov A.; Kuzmin, Yaroslav V.; Dementiev, Vyacheslav N. (Department of Geosciences, The University of Arizona, 2004-01-01)
      A review of the radiocarbon chronology of some late Upper Pleistocene mammals from Siberia is presented. Previously published data has been supplemented by new 14C dates for 5 species (woolly mammoth, woolly rhinoceros, bison, horse, and muskox) to reconstruct chronological extinction patterns. The final extinction of woolly rhinoceros and bison in Siberia can be dated to approximately 11,000-9700 BP, but some megafaunal species (woolly mammoth, horse, and muskox) survived into the Late Holocene, about 3700-2200 BP.
    • Ages of Ostracodes from Pleistocene Lake Sediments of the Western Great Basin, USA—Results of Progressive Acid Leaching

      Hajdas, Irka; Bonani, Georges; Zimmerman, Susan Herrgesell; Mendelson, Millie; Hemming, Sidney (Department of Geosciences, The University of Arizona, 2004-01-01)
      Progressive dissolution experiments were performed on samples of ostracode shells from lacustrine sediments from the western Great Basin to remove contamination of the surface by secondary calcite. The observed age differences between the external and residual fractions were as great as 2000 to 6000 yr. A "plateau" in ages of the last fractions was obtained only for 1 sample; however, results of repeated experiments resulted in very good agreement of the final ages. A comparison with previously published chronologies based on bulk radiocarbon ages of ostracodes from Wilson Creek (Benson et al. 1990) shows that leaching is imperative for dating samples older than 20 ka BP. This study focuses on the problem of contamination and its removal. However, the final chronology of the Wilson Creek Formation (and other late Pleistocene lacustrine sediments) will require additional dating of other sections as well as establishment of a reservoir effect correction.
    • Capabilities of the New SUERC 5MV AMS Facility for 14C Dating

      Xu, S.; Anderson, R.; Bryant, C.; Cook, G. T.; Dougans, A.; Freeman, S.; Naysmith, P.; Schnabel, C.; Scott, E. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      A new National Electrostatic Corporation (NEC) 5MV accelerator mass spectrometer became operational at the Scottish Universities Environmental Research Centre (SUERC) in July 2002. It has 2 Cs sputter negative ion sources: a 134-sample source (S1) for the routine measurement of all species, and a hybrid source (S2) with 40 spaces for radiocarbon measurements with either graphite or CO2 samples. A number of performance tests on graphite samples have been carried out on both sources. A precision of better than 0.3% is feasible for modern samples on a routine basis. The 14C background of the machine and the graphite preparation process blank are 0.04 +/0.01 and 0.16 +/0.05 pMC, respectively, indicating that 14C dating back to approximately 50 kyr BP is possible. The normalized 14C values for a series of reference materials agree well with the IAEA, TIRI, and FIRI consensus values. Routine measurement of 14C has been underway since May 2003. Preliminary results of performance tests on the CO2 gas ion source are also reported.
    • Calculating Sediment Compaction for Radiocarbon Dating of Intertidal Sediments

      Bird, M. I.; Fifield, L. K.; Chua, S.; Goh, B. (Department of Geosciences, The University of Arizona, 2004-01-01)
      This study estimates the maximum and minimum degrees of autocompaction for radiocarbon-dated Holocene mangrove sediments in Singapore, in order to correct apparent sediment accretion rates for the effects of sediment compression due to autocompaction. Relationships developed for a suite of modern (surface) sediment samples between bulk density, particle-size distribution, and organic matter content were used to estimate the initial (uncompacted) bulk density of buried and variably compressed Holocene sediments, based on the grain-size distribution and organic matter content of the sediment. The difference between measured (compacted) and initial (uncompacted) bulk density of each buried sediment interval can be interpreted as the amount of length shortening experienced by each interval since burial. This allows the elevation of samples selected for 14C dating to be corrected for the effects of autocompaction of the underlying sediment sequence, so that accurate estimates of vertical sediment accretion rates can be calculated. The 3 Holocene mangrove sequences analyzed and dated for this study ranged in age from 2000 to 8500 cal BP. The effects of autocompaction are significant, even in comparatively thin sequences, with subsidence of up to 56 cm calculated for carbon-dated samples presently 2 m above incompressible basement. The vertical sediment accretion rates for these mangrove sequences ranged from 0.99 to 6.84 mm/yr and carbon sequestration rates ranged from 0.9 to 1.7 t/ha/yr, all within the range observed for comparable Holocene and modern mangrove sediments elsewhere.
    • Rehabilitation of the Laboratoire de Carbone 14-Dakar (Senegal) with a Super Low-Level Liquid Scintillation Counting System

      Ndeye, Maurice; Ka, Oumar; Bocoum, Hamady; Diallo, Alpha O. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Following the passing of Prof Cheikh Anta Diop in 1986, the radiocarbon laboratory (LC14) he created 20 yr earlier at the Institut Francophone d'Afrique Noire (IFAN), Dakar, Senegal, fell into a long hibernation. It took nearly 3 yr to renovate the laboratory and reinstall new equipment in order to return LC14 to full functionality and resume its activity. A new dating system has been implemented around a super low-level liquid scintillation spectrometer from Packard, the Tri-Carb 3170TR/LS, located in an underground room. In this paper, we assess the performance of the dating setup (background level and figure of merit) using known samples from Paris 6 and international standards from the International Atomic Energy Agency (IAEA). After the calibration, the setup was used to study bole seashells from the Khant area in the northern part of Senegal (West Africa). The aim is to present evidence of the correlation between the transgression of the Nouakchottan (5500 BP) and a few industries in the Khant area. The corresponding ages are difficult to assess and the dates available for this cultural site are randomly distributed, ranging from 4500 to 1500 BP, i.e., a chronological period spanning from the Neolithic to the Iron Age.
    • Simulation Study for the Separation of Rare Isotopes at the Seoul National University AMS Facility

      Yun, C. C.; Lee, C. S.; Youn, M.; Kim, J. C. (Department of Geosciences, The University of Arizona, 2004-01-01)
      A simulation study for the separation of rare isotopes such as beryllium and aluminum was performed for a new beam line to be attached to the 3MV Tandetron accelerator at the accelerator mass spectrometry (AMS) facility of Seoul National University in Korea. The new beam line will also be used for other scientific applications, namely, ion implantations, Rutherford backscattering, and nuclear astrophysics experiments. It mainly consists of 30 degrees and 100 degrees deflection dipole magnets and drift spaces. A transfer matrix for the beam line was determined by the TRANSPORT code. Simulation of the rare isotope separation was performed by a ray tracing method using the TURTLE code. The simulation results, including the effect of the energy degrader, provide feasibility for the separation of isobars with small mass differences in 10Be10B and 26Al-26Mg.
    • Source Apportionment of Aerosols by 14C Measurements in Different Carbonaceous Particle Fractions

      Szidat, S.; Jenk, T. M.; Gäggeler, H. W.; Synal, H.-A.; Fisseha, R.; Baltensperger, U.; Kalberer, K.; Samburova, V.; Wacker, L.; Saurer, M.; et al. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Radiocarbon enables a distinction between contemporary and fossil carbon, which can be used for the apportionment of biogenic and anthropogenic sources in environmental studies. In order to apply this approach to carbonaceous atmospheric aerosols, it is necessary to adapt pretreatment procedures to the requirements of 14C measurements. In this work, we followed an approach in which total carbon (TC) is subdivided into fractions of different chemical and physical properties. 14C data of ambient aerosols from Zrich (Switzerland) are presented for the 2 sub-fractions of TC, organic carbon (OC) and elemental carbon (EC). Furthermore, OC is separated into water-insoluble OC (WINSOC) and water-soluble OC (WSOC). Results demonstrate the importance to differentiate between these fractions for 14C-deduced source apportionment, as the contributions can range between both extremes, nearly exclusively biogenic and anthropogenic.
    • Temporal Variation of Radiocarbon Concentration in Airborne Particulate Matter in Tokyo

      Shibata, Ken; Yamamoto, Naomichi; Endo, Michio; Yoshinaga, Jun; Yanagisawa, Yukio; Endo, Osamu; Goto, Sumio; Yoneda, Minoru; Shibata, Yasuyuki; Morita, Masatoshi (Department of Geosciences, The University of Arizona, 2004-01-01)
      The temporal radiocarbon variation (in terms of percent Modern Carbon: pMC) of size-fractionated airborne particulate matter (APM) collected in Tokyo between April 2002 and February 2003 was analyzed in order to get an insight into the sources of carbonaceous particles. Results indicated significant biogenic origins (approximately 40 pMC on average). In general, the seasonal and particle size variations in pMC were relatively small, with 2 exceptions: elevated pMC in coarse particles in April and October 2002, and relatively low pMC in the finest particle size fraction collected in August 2002. The former finding could be tentatively attributed to the abundance of coarse particles of biological origins, such as pollen; the latter might be due to an increased fraction of anthropogenic secondary particles.
    • Development of a Combustion System for Liquid or Gas Samples

      Park, J. H.; Lee, C. S. (Department of Geosciences, The University of Arizona, 2004-01-01)
      While it is customary to use solid samples for measuring the 14C/12C ratio, it is sometimes necessary to handle liquid or gas samples. Motivated by a scientific purpose to count radiocarbon yields in deuterated acetone irradiated with energetic neutrons, we developed a new combustion system to treat liquid or gas samples. In contrast with the typical combustion system using CuO for solid samples, the new combustion system uses high-purity O2 (99.999%) gas. As an initial investigation, we combusted deuterated acetone (acetone-d6, certified 100.0 atm % D) to make CO2 under the ambient O2 pressure. The resulting CO2 gas then went through the reduction process to form graphite for further accelerator mass spectrometry (AMS) measurement.
    • Direct Coupling of an Elemental Analyzer and a Hybrid Ion Source for AMS Measurements

      Uhl, Thomas; Kretschmer, Wolfgang; Luppold, Wolfgang; Scharf, Andreas (Department of Geosciences, The University of Arizona, 2004-01-01)
      The requests to measure many samples, and samples with very low carbon masses, make it necessary to develop new techniques in sample handling to accelerate sample preparation and to eliminate carbon contamination. Our 40 MC-SNICS was recently modified to a hybrid ion source. To run the hybrid ion source with a gas parameter, settings were studied and a gas handling system for the direct coupling of an elemental analyzer and a gas ion source was developed.
    • Measurement of Low 14C Activities in a Liquid Scintillation Counter in the Zagreb Radiocarbon Laboratory

      Horvatinčić, Nada; Barešić, Jadranka; Krajcar Bronić, Ines; Obelić, Bogomil (Department of Geosciences, The University of Arizona, 2004-01-01)
      Two methods of chemical preparation of radiocarbon samples are implemented in the Zagreb Radiocarbon Laboratory for measurement by a new liquid scintillation counter (LSC), Quantulus 1220(TM): a CO2 absorption method (LSC-A) and a benzene synthesis method (LSC-B). For samples prepared by both methods, the optimal counting windows for measurement in LSC were determined. The total efficiency of LSC-A is 65% and that of the LSC-B is 83%, while the corresponding 14C dating limits are 31,800 yr and 52, 160 yr, respectively. 14C activities measured by the LSC-A and LSC-B methods were compared with those measured by the gas proportional counter (GPC) method (efficiency 75%, 14C dating limit 37,500 yr). The results obtained by the LSC-A method have larger errors than those measured by the GPC method, but LSC-A is quick, inexpensive, simple, and requires less carbon than the GPC method. Thus, LSC-A is suitable for 14C measurements of geological, hydrological, and environmental samples. On the other hand, the results obtained by the LSC-B method give smaller errors and a larger 14C dating range. Therefore, LSC-B is more suitable for 14C dating of archaeological samples.
    • Neolithic Massacres: Local Skirmishes or General Warfare in Europe?

      Stadler, Peter; Häußer, Annemarie; Kutschera, Walter; Steier, Peter; Teschler-Nicola, Maria; Wahl, Joachim; Windl, Helmut J. (Department of Geosciences, The University of Arizona, 2004-01-01)
      The Neolithic site of Schletz in Lower Austria comprises a fortified settlement from the end of the Linearbandkeramik (LBK) culture. Large numbers of human bones were found at the base of the fortification ditches, and many of the excavated bones and skulls showed evidence of trauma which most likely originates from violence. This remarkable deposit of human remains has been considered evidence for an abrupt end to the Early Neolithic settlement at Schletz. In order to investigate this interpretation, radiocarbon accelerator mass spectrometry (AMS) measurements of human bone samples from this site were performed at VERA. The X2 test of the results from specimens with clearly identified lesions suggests that these may be contemporaneous. Further, it may be concluded that all individuals with evidence of trauma from Schletz were probably the victims of a single event: a massacre at the end of the LBK. Similar evidence is found at Early Neolithic sites at Talheim and Herxheim in the western part of Germany. Analysis of the 14C ages of bones from both sites suggests that the Talheim event may have been coeval with the massacre of Schletz, whereas an event at Herxheim might have happened some time earlier. For Herxheim, the massacre theory is still under discussion, and a change in the burial rite is also considered as an alternative interpretation.
    • Fast and Accurate Sequential Injection AMS with Gated Faraday Cup Current Measurement

      Klein, M.; Mous, D. J. W.; Gottdang, A. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Sequential injection or bouncing has a number of properties which can lead to a reduction of the analysis accuracy if no appropriate measures are taken. A special injection system has been developed in order to eliminate these shortcomings. The influence of source glitches or instabilities on the measured isotopic ratio is substantially reduced by a high cycling frequency. A fast beam-blanking unit guarantees the needed accuracy of the injection periods. Background currents are avoided by synchronizing the current measurement for the stable isotopes with their injection periods. To achieve the required speed and precision of the gated measurement, new instrumentation was developed. The elimination of background contributions allows an efficiency for radiocarbon counting as high as 95% at a cycling frequency of 100 Hz.
    • Extraction and AMS Dadiocarbon Dating of Pollen from Lake Baikal sediments

      Piotrowska, Natalia; Bluszcz, Andrzej; Demske, Dieter; Granoszewski, Wojciech; Heumann, Georg (Department of Geosciences, The University of Arizona, 2004-01-01)
      This work focuses on the preparation and dating of sporomorph (pollen and spores) concentrates of high purity. Three sediment cores recovered from Lake Baikal within the EU-Project CONTINENT were subjected to palynological analyses and accelerator mass spectrometry (AMS) radiocarbon dating. Laboratory processing of concentrates was aimed at the removal of non-sporomorph organic matter by means of chemical treatment, micro-sieving, and heavy liquid separation. The obtained concentrates were checked under the microscope and sample purity was estimated on the basis of particle counts. The results of AMS 14C dating show differences in the sedimentation rate among 3 sites of Lake Baikal.
    • Magnesium Perchlorate as an Alternative Water Trap in AMS Graphite Sample Preparation: A Report on Sample Preparation at KCCAMS at the University of California, Irvine

      Santos, G. M.; Southon, J. R.; Druffel-Rodriguez, K. C.; Griffin, S.; Mazon, M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      We present a brief discussion of sample preparation procedures at the Keck Carbon Cycle Accelerator Mass Spectrometer (KCCAMS), University of California, Irvine, and a systematic investigation of the use of Mg(ClO4)2 as an absorptive water trap, replacing the standard dry ice/ethanol cold finger in graphite sample preparation. We compare high-precision AMS measurement results from oxalic acid I and USGS coal samples using Mg(ClO4)2 under different conditions. The results obtained were also compared with those achieved using the conventional water removal technique. Final results demonstrate that the use of Mg(ClO4)2 as an alternative water trap seems very convenient and reliable, provided the Mg(ClO4)2 is replaced frequently.
    • Initial Results with Low Energy Single Stage AMS

      Schroeder, J. B.; Hauser, T. M.; Norton, G. A.; Klody, G. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      The National Electrostatics Corporation has built and tested a prototype low energy, open-air, single stage carbon accelerator mass spectrometry (AMS) system (patent pending). The configuration tested has a standard 40-sample, multicathode SNICS source on a 300-kV deck. The beam is mass analyzed before acceleration to a gas stripper located at ground. The 14C+ ions are separated from 13C+ and super 12C+ arising from the molecular breakup by a 90 degrees analyzing magnet immediately after the gas stripper which acts as a molecular dissociator. The 14C+ beam passes through an electrostatic spherical analyzer before entering the particle detector. The observed 14C/12C precision is better than 5 per mil with a sensitivity of better than 0.05 dpm/gmC. A first single stage AMS system has been ordered. The configuration of this system will be discussed.
    • Lugovskoe, Western Siberia: A Possible Extra-Arctic Mammoth Refugium at the End of the Late Glacial

      Orlova, Lyobov A.; Zenin, Vasily N.; Stuart, Anthony J.; Higham, Thomas F. G.; Grootes, Pieter M.; Leshchinsky, Sergei V.; Kuzmin, Yaroslav V.; Pavlov, Aleksander F.; Maschenko, Evgeny N. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Eleven woolly mammoth bone samples from Lugovskoe (central West Siberian Plain, Russia) were radiocarbon dated in 3 laboratories: Institute of Geology, Novosibirsk; Oxford University, Oxford; and Christian Albrechts University, Kiel. Each laboratory used its own protocol for collagen extraction. Parallel dating was carried out on 3 samples in Novosibirsk and Oxford. Two results are in good agreement. However, there is a major discrepancy between 2 dates obtained for the third sample. The dates obtained so far on the Lugovskoe mammoths range from about 18,250 BP to about 10,210 BP. The Lugovskoe results thus far confirm the possibility of woolly mammoth survival south of Arctic Siberia in the Late Glacial after about 12,000 BP, which has important implications for interpreting the process of mammoth extinction. The site has also produced the first reliable traces of human occupation from central Western Siberia at the Late Glacial, including unique direct evidence of mammoth hunting.