• 14C Ages of 43 Consecutive Single-Year Tree Rings Between 2710 and 2655 cal BP Using Accelerator Mass Spectrometry

      Suzuki, Kayo; Sakurai, Hirohisa; Takahashi, Yui; Gunji, Shuichi; Tokanai, Fuyuki; Matsuzaki, Hiroyuki; Sunohara, Yoko (Department of Geosciences, The University of Arizona, 2007-01-01)
      We have measured the radiocarbon ages of 43 consecutive single-year tree rings using accelerator mass spectrometry (AMS) with a statistical accuracy of -2.3 AMS 14C ages of the 36 viable samples are between 2708 and 2666 cal BP, a period in which the 14C of the IntCal04 curve (Reimer et al. 2004) shows an enhancement. The 14C ages of the samples are scattered with a Gaussian distribution around the interpolated IntCal04 calibration curve. The time profile of the deviations of the 36 14C ages from the interpolated IntCal04 calibration curve indicates a linear trend and a characteristic variability rather than a random fluctuation around the curve. The trend indicates a higher gradient than that of the interpolated IntCal04 calibration curve. The profile implies a periodic variation of approximately 11 yr and an amplitude of roughly 18 14C yr.
    • 14C Ages of a Varved Last Glacial Maximum Section Off Pakistan

      von Rad, Ulrich; Sarnthein, Michael; Grootes, Pieter M.; Doose-Rolinski Heidi; Erbacher, Jochen (Department of Geosciences, The University of Arizona, 2003-01-01)
      In a core off Pakistan, we obtained 38 14C analyses by accelerator mass spectrometry (AMS) from a 4.4-m-thick, expanded, annually-laminated Last Glacial Maximum (LGM) section, bracketed by bioturbated intervals ascribed to the Heinrich-1 (H1) and Heinrich-2 (H2) equivalent events (52 14C analyses between 24-15 kyr BP). A floating varve age scale, anchored to the oxygen isotope record of the layer-counted GISP2 ice core at the H2/LGM boundary, results in an annually dated record for the LGM from 23,450-17,900 cal BP. The floating varve scale of the LGM provides us with a tentative calibration of local marine AMS 14C age dates to calendar years.
    • 14C Ages of Bone Fractions from Armenian Prehistoric Sites

      Cherkinsky, A.; Chataigner, C. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Prehistoric cultures in Armenia are still poorly known; thus, accelerator mass spectrometry (AMS) radiocarbon dates are invaluable in constructing an accurate chronology. Bone samples have been collected from sites representing the Middle Paleolithic, Chalcolithic, and Early Bronze periods. Most of the bone samples are poorly preserved. We describe the separation technique for the extraction of both the bioapatite and collagen fractions. In many cases where the bone had very low organic material content, the collagen fractions yielded a younger age, although the ages of bioapatite fractions were found to be in good agreement with associated archaeological artifacts. In cases where bone was well preserved, both fractions exhibited ages in good agreement with the artifacts. The accuracy of 14C dating of bone material always depends on its degree of preservation, and each case should be carefully evaluated to determine which fraction is less contaminated in order to accurately date a burial event.
    • 14C Ages of Tephra Layers from the Holocene Deposits of Kunashir Island (Russian Far East)

      Razjigaeva, N. G.; Grebennikova, T. A.; Ganzey, L. A.; Bazarova, V. B.; Mokhova, L. M.; Korotky, A. M.; Sulerzhitsky, L. D. (Department of Geosciences, The University of Arizona, 1998-01-01)
      Holocene deposits from the central and southern regions of the Kunashir Island contain tephra from 12 volcanic eruptions (Kn1-12). We studied radiocarbon data, mineralogical composition, and distribution of the tephra layers in different Holocene facies. The main sources of the Holocene tephra samples were the volcanoes of Hokkaido Island. The distribution of ash layers on Kunashir Island allows us to estimate their direction. Ash layers can be reliable markers for age determination of different coastal landforms on open oceanic shores. We propose here a tephrastratigraphical scheme for different Middle-Late Holocene facies.
    • 14C Ages of Terrestrial Macrofossils from Lago Grande di Monticchio (Italy)

      Hajdas, Irka; Bonani, Georges; Zolitschka, Bernd; Brauer, Achim; Negendank, Jörg W. (Department of Geosciences, The University of Arizona, 1998-01-01)
      Lago Grande di Monticchio (Italy) contains long sedimentary records of >75 ka (Zolitschka and Negendank 1996). In a joint European project (Creer and Thouveny 1996), vegetation history and climatic changes for this part of the Mediterranean have been reconstructed (Watts, Allen and Huntley 1996; Watts et al. 1996). In addition to the time scale based on annual laminations and sedimentation rate, tephra layers and pollen spectra, radiocarbon dating was applied for the last 40 ka. Previous studies have shown that the age of bulk sediment from Lago Grande di Monticchio, which is a maar lake at the flanks of Mt. Vulture, was influenced by "dead carbon" of volcanic origin dissolved in the lake water. Thus, 14C dating of the record is problematic and must be limited to dating macrofossils of terrestrial origin. From a set of sediment samples, macrofossils were selected and dated using accelerator mass spectrometry (AMS). A 14C time scale based on seven data points between 9000 and 24,000 BP is compared with other dating of the record based on varve counting and tephrochronology (Zolitschka 1996).
    • 14C AMS at SUERC: Improving QA Data with the 5MV Tandem and 250kV SSAMS

      Naysmith, P.; Cook, G. T.; Freeman, S. T.; Scott, E. M.; Anderson, R.; Xu, S.; Dunbar, E.; Muir, G. P.; Dougans, A.; Wilcken, K.; et al. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In 2003, a National Electrostatics Corporation (NEC) 5MV tandem accelerator mass spectrometer was installed at SUERC, providing the radiocarbon laboratory with 14C measurements to 4-5 repeatability. In 2007, a 250kV single-stage accelerator mass spectrometer (SSAMS) was added to provide additional 14C capability and is now the preferred system for 14C analysis. Changes to the technology and to our operations are evident in our copious quality assurance data: typically, we now use the 134-position MC-SNICS source, which is filled to capacity. Measurement of standards shows that spectrometer running without the complication of on-line 13C evaluation is a good operational compromise. Currently, 3 14C/13C measurements are routinely achieved for samples up to nearly 3 half-lives old by consistent sample preparation and an automated data acquisition algorithm with sample random access for measurement repeats. Background and known-age standard data are presented for the period 2003-2008 for the 5MV system and 2007-2008 for the SSAMS, to demonstrate the improvements in data quality.
    • 14C AMS Dating of Icelandic Lake Sediments

      Sveinbjörnsdóttir, Árný E.; Heinemeier, Jann; Kristensen, Peter; Rud, Niels; Geirsdóttir, Áslaug; Harđardóttir, Jóhann (Department of Geosciences, The University of Arizona, 1998-01-01)
      We report an age-depth profile for the sediments of the Lake Hestvatn, southern Iceland, based on 14C analyses of the organic fraction of bulk sediment samples, molluscs and foraminifera. Our age-depth curve is supported by the occurrence of the well-dated Vedde ash in the lowermost part of the sediments. Comparison of foraminifera dates with the age of the Vedde ash indicates a reservoir age of ca. 400 yr. The results suggest that the sediments at Hestvatn accumulated in a marine environment until ca. 8700 BP and thereafter in freshwater. Owing to the lack of terrestrial macrofossils and the low concentration of molluscs and foraminifera, we were forced to attempt to date most of the core with the organic fraction of the bulk sediment samples. We found, however, that this fraction is not homogeneous in density or 14C age. We believe that during sample pretreatment we managed to isolate a light organic fraction, which closely represents the true age of the sediment, whereas the denser fraction yields ages that are too high. This age diversity may to some extent be explained by the large drainage area of the lake, from which plant remains of different ages may have been washed into the lake.
    • 14C AMS Dating the Transition from the Paleolithic to the Neolithic in South China

      Yuan, Sixun; Zhou, Guoxing; Guo, Zhiyu; Zhang, Zimo; Gao, Shijun; Li, Kun; Wang, Jiangjun; Liu, Kexing; Li, Bin; Lu, Xiangyang (Department of Geosciences, The University of Arizona, 1995-01-01)
      To study the transition from the Paleolithic to the Neolithic period and its duration, samples of charcoal, bone, flowstone and shells excavated from Bailiandong and Miaoyan caves, Guangxi Zhuang autonomous region, South China were dated using the Peking University AMS facility and liquid scintillation counter. The remains excavated from these sites show typical characteristics of the transition from the Paleolithic to the Neolithic. Radiocarbon dating results show a rapid transition from ca. 20 to 10 ka BP.
    • 14C AMS Measurements of <100 Microgram Samples with a High-Current System

      von Reden, K. F.; McNichol, Ann P.; Pearson, Ann; Schneider, Robert J. (Department of Geosciences, The University of Arizona, 1998-01-01)
      The NOSAMS facility at Woods Hole Oceanographic Institution has started to develop and apply techniques for measuring very small samples on a standard Tandetron accelerator mass spectrometry (AMS) system with high-current hemispherical Cs sputter ion sources. Over the past year, results on samples ranging from 7 to 160 micrograms C showed both the feasibility of such analyses and the present limitations on reducing the size of solid carbon samples. One of the main factors affecting the AMS results is the dependence of a number of the beam optics parameters on the extracted ion beam current. The extracted currents range from 0.5 to 10 micro-A of 12Cfor the sample sizes given above. We here discuss the setup of the AMS system and methods for reliable small-sample measurements and give the AMS-related limits to sample size and the measurement uncertainties.
    • 14C Analyses of Groundwater from the Botucatu Aquifer System in Brazil

      Silva, Annkarin Aurelia Kimmelmann E.; da Cunha Rebouças, Aldo; Freitas Santiago, Maria Marlucia (Department of Geosciences, The University of Arizona, 1989-01-01)
      Measurements of 14C activity as well as determinations of the stable isotope composition (18O, 2H and 13C) of groundwater samples were made to investigate the flow path, origin, recharge and age of the Botucatu Aquifer System in Brazil, between 1984 and 1987. The stable oxygen isotope composition reflects infiltration during several climatic recharge conditions. Measured 14C activities range from 0.4 to 94.2% modern. delta-13C values enable us to distinguish two groundwater types of different origins. There is a gradual increase of 14C ages from the outcrop area towards the central part of the basin, associated with a progression of the confining conditions. Anomalous fluoride contents seem to be correlated with high 14C ages of the groundwater. The reliability of the 14C data is discussed.
    • 14C Analysis of Annual Tree Rings from the Vicinity of the Chernobyl NPP

      Buzinny, Michael; Likhtarev, Ilja; Los', Ivan; Talerko, Nikolay; Tsigankov, Nikolay (Department of Geosciences, The University of Arizona, 1998-01-01)
      Samples of >40 pine trees were collected from around the Chernobyl NPP for radiocarbon measurement, to determine the spatial distribution of excessive 14C in tree rings from 1986 consequent upon accidental radiocarbon release. Tree samples were collected during 1995-1996 from sites situated at distances >2.5 km from the NPP and covering a variety of directions in relation to the NPP. To evaluate Delta-14C for 1986 annual rings, we compared 14C levels for separate 1985-1987 annual rings, taking into account the trend of operational releases. Early and late wood samples for 1986 annual tree rings were measured separately to increase the sensitivity and precision of measurements. The maximum value observed for excessive accidental radiocarbon levels (Delta-14C) was found to be 124 pMC (281.6 Bq kg-1 C). We present Delta-14C values for examined sites; their spatial distribution shows a high irregularity of atmospheric 14C depending on direction from the NPP. Using obtained data, we reconstruct the temporal behavior of 14C release during the Chernobyl accident with the aid of atmospheric transport modeling. The total amount of 14C released from 26 April to 5 May 1986 has been estimated as 44 TBq.
    • 14C and 18O in Siberian Syngenetic Ice-Wedge Complexes

      Vasil'chuk, Y. K.; Vasil'chuk, A. C. (Department of Geosciences, The University of Arizona, 1998-01-01)
      We discuss the possibility of dating ice wedges by the radiocarbon method. We show as an example the Seyaha, Kular and Zelyony Mys ice wedge complexes, and investigated various organic materials from permafrost sediments. We show that the reliability of dating 18O variations from ice wedges can be evaluated by comparison of different organic materials from host sediments in the ice wedge cross sections.
    • 14C and 234U-Excess Dating of Groundwater in the Haifa Bay Region, Israel

      Rogojin, Vasily; Carmi, Israel; Kronfeld, Joel (Department of Geosciences, The University of Arizona, 1998-01-01)
      Radiocarbon activities and uranium isotopic disequilibria were measured in water samples from both the sandy Pleistocene coastal aquifer and within the upper Cretaceous Judea Group carbonate aquifer of northwestern Israel. The samples in both aquifers exhibit a decrease in 14C activity that is concomitant to the growth in 234U-excess. This suggests that under specific conditions, 234U-excess dating of groundwater can be used to corroborate 14C dates, while offering the possibility of extending the range of dating of groundwater beyond that of 14C.
    • 14C and Other Parameters During the Younger Dryas Cold Phase

      Oeschger, Hans; Welten, Max; Eicher, Ulrich; Möll, Markus; Riesen, Trudi; Siegenthaler, Ulrich; Wegmüller, Samuel (American Journal of Science, 1980-01-01)
      Pollen analysis as well as 18O/16O results on lake marl show that the Younger Dryas climatic period, between about 11,000 and 10,300 BP, was the last vigorous cold phase of the Wurm Glacial. Detailed 14C analyses from a peat bog near Wachseldorn (Switzerland) point to a 14C anomaly in this period. Further indication of a 14C anomaly is given by the observation that, during the Younger Dryas period, the sedimentation rates in several lakes apparently were higher than in adjacent periods; an explanation might be that the 14C time scale was compressed between 11,000 and 10,000 BP, ie, the atmospheric 14C/C ratio varied. If real, this suggested 14C variation would probably be connected to the climatic events during this transition period from Later Glacial to Postglacial.
    • 14C and the Iron Age Chronology Debate: Rehov, Khirbet En-Nahas, Dan, and Megiddo

      Finkelstein, Israel; Piasetzky, Eli (Department of Geosciences, The University of Arizona, 2006-01-01)
      A recently published volume, the Bible and Radiocarbon Dating: Archaeology, Text and Science (Levy and Higham 2005), provides data related to the debate over the chronology of the Iron Age strata in the Levant (for a review, see Carmi 2006). The present article comments on several chapters in the volume. The article highlights methodological problems, such as insecure stratigraphic provenance of 14C samples, and demonstrates how unjustified selection of data can bias the result. The article offers a new interpretation to some of the results and shows that the full set of measurements from Tel Rehov supports the Low Chronology system.
    • 14C Background Levels in an Accelerator Mass Spectrometry System

      Vogel, J. S.; Nelson, D. E.; Southon, J. R. (American Journal of Science, 1987-01-01)
      The levels and sources of the measurement background in an AMS 14C dating system have been studied in detail. The relative contributions to the total background from combustion, graphitization, storage, handling, and from the accelerator were determined by measuring the 14C concentrations in samples of anthracite coal ranging in size from 15 micrograms to 20mg. The results show that, for the present system, the uncertainty in the background is greater than that due to measurement precision alone for very old or for very small samples. While samples containing 100 micrograms of carbon can yield useful 14C dates throughout the Holocene, 200 to 500 micrograms are required for dating late Pleistocene materials. With the identification of the procedures that introduce contamination, the level and uncertainty of the total system background should both be reducible to the point that 100 micrograms of carbon would be sufficient for dating most materials.
    • 14C Calibration Curves for Modern Plant Material from Tropical Regions of South America

      Ehleringer, James R.; Casale, John F.; Barnette, Janet E.; Xu, Xiaomei; Lott, Michael J.; Hurley, Janet (Department of Geosciences, The University of Arizona, 2011-12-16)
      Two 14C calibration curves have been produced that allow determination of the statistical average age of coca leaf and cocaine base specimens produced for the time period 19792009. These calibration curves are based on field collections of specimens in Bolivia, Colombia, Ecuador, and Peru. The coca leaf F14C and 14C calibration curves can be used to predict the ages of botanical tissues collected in tropical South America and possibly extended to other tropical locations. The cocaine F14C and 14C calibration curves can be used to predict the ages of seized cocaine specimens. Because the 14C of the atmosphere is diminishing, the precision of this approach for age determinations will continue to get less precise over time as atmospheric 14C content continues to decline.
    • 14C Calibration in the 2nd and 1st Millennia BC—Eastern Mediterranean Radiocarbon Comparison Project (EMRCP)

      Kromer, Bernd; Manning, Sturt W.; Friedrich, Michael; Talamo, Sahra; Trano, Nicole (Department of Geosciences, The University of Arizona, 2010-01-01)
      We have measured additional known-age German oak samples in 4 intervals in the 2nd and 1st millennia BC to add to (and to replicate) parts of the international Northern Hemisphere radiocarbon calibration data set. In the 17th, 16th, and 12th centuries BC, our results agree well with IntCal04. In the 14th and 13th centuries BC, however, we observe a significant offset, with our results on average 27 yr older than IntCal04. The previously reported 14C offset between Anatolian juniper trees and central European oaks in the 9th and 8th centuries BC is smaller now, on the basis of our new measurements of German oak, but still evident. In the 17th and 16th centuries BC, the 14C ages from the Anatolian chronology agree well with IntCal04 and our new German oak data.
    • 14C Calibration in the Southern Hemisphere and the Date of the Last Taupo Eruption: Evidence from Tree-Ring Sequences

      Sparks, R. J.; Melhuish, W. H.; McKee, J. W. A.; Ogden, John; Palmer, J. G.; Molloy, B. J. (Department of Geosciences, The University of Arizona, 1995-01-01)
      Tree rings from a section of Prumnopitys taxifolia (matai) covering the period AD 1335-1745 have been radiocarbon dated and used to generate a 14C calibration curve for southern hemisphere wood. Comparison of this curve with calibration data for northern hemisphere wood does not show a systematic difference between 14C ages measured in the northern and southern hemispheres. A floating chronology covering 270 yr and terminating at the last Taupo (New Zealand) eruption, derived from a sequence of 10-yr samples of tree rings from Phyllocladus trichomanoides (celery pine, or tanekaha), is also consistent with the absence of a systematic north-south difference, and together with the matai data, fixes the date of the Taupo eruption at AD 232 +/15.
    • 14C Chronology of Archaeological Sites in European Russia and Changes in Environmental Processes: A Database Investigation

      Zaitseva, Ganna I.; Dergachev, Valentin A.; Timofeev, Vladimir; Sementsov, Anatoly A. (Department of Geosciences, The University of Arizona, 1998-01-01)
      A large number of 14C dates for archaeological sites in European Russia have been entered into a new database. The database includes >1500 dates for ca. 500 archaeological sites. Because European Russia is a very large area, the database includes subdivisions of territories and regions. We analyzed our 14C dates according to archaeological periods (Paleolithic through Medieval period) and made a comparison with environmental (climatic) parameters. Our database for archaeological sites and monuments offers new possibilities for correlation between the development of ancient cultures and natural-climatic processes.