• Radiocarbon Dates from Halfiah Gibli (Abadiyeh), a Predynastic Settlement in Upper Egypt

      Bard, Kathryn A. (Department of Geosciences, The University of Arizona, 2003-01-01)
      In 1989 and 1991, wood charcoal samples were excavated at a Predynastic settlement in Upper Egypt, Halfiah Gibli (HG). A second site, Semaineh (SH), was also investigated, but as the ceramics there were mostly from the Old Kingdom, excavations were concentrated at HG. Wood charcoal was obtained in undisturbed contexts, in association with Nagada culture potsherds and lithics, ranging in date from about 3700 BC to 3200/3100 BC. These new radiocarbon dates provide more data for the relative phases of the Nagada culture, formulated mainly from ceramic seriation.
    • Bomb Radiocarbon in Tree Rings from Northern New South Wales, Australia: Implications for Dendrochronology, Atmospheric Transport, and Air-Sea Exchange of CO2

      Hua, Quan; Barbetti, Mike; Zoppi, Ugo; Chapman, David M.; Thomson, Bruce (Department of Geosciences, The University of Arizona, 2003-01-01)
      We have analyzed by radiocarbon 27 consecutive single rings, starting from AD 1952, of a preliminarily cross-dated section (DFR 021) of Pinus radiata, which grew in Armidale, northern New South Wales, Australia. The bomb 14C results suggested the possibility of 2 false rings, and, consequently, 2 misidentified rings in the preliminary count for this section. This possibility was supported by a better ring-width correlation between the revised DFR 021 count and other Pinus radiata chronologies in the study region. This indicated that bomb 14C is a useful tool to complement the standard techniques of dendrochronology in tree species where annual rings are not always clearly defined. Our accelerator mass spectrometry (AMS) 14C results for Armidale Pinus radiata, on a corrected timescale, can be compared with previously published atmospheric and oceanic 14C data. The data show interesting features of atmospheric circulation and the regional air-sea exchange of CO2 for the bomb period. On average, the difference between Delta-14C values for Armidale (30 degrees S) and those for Tasmania (42 degrees S) was negligible, implying a small latitudinal 14C gradient in the Southern Hemisphere. However, small offsets between Armidale and Tasmania were observed for some periods. The variation of these offsets suggests some slight changes in the relative contributions of the 2 excess 14C sources (the northern troposphere and southern stratosphere) to the southern troposphere. In the decay of bomb 14C, atmospheric 14C reached a global equilibrium at the end of the 1960s and decreased exponentially, halving every 16 years. The time for air-sea exchange of CO2 for southern Pacific mid-latitudes was found to be about 7.5 yr, which was equivalent to a CO2 flux from the atmosphere to the oceans of 21.5 moles m-2 y-1 for the 1970s.
    • Reply to Israel Carmi (2002): "Are the 14C Dates of the Dead Sea Scrolls Affected by Castor Oil Contamination?"

      Rasmussen, Kaare L.; van der Plicht, Johannes; Doudna, Gregory; Cross, Frank M.; Strugnell, John (Department of Geosciences, The University of Arizona, 2003-01-01)
    • Balanced Window Method in 14C Liquid Scintillation Counting

      Theodórsson, P.; Ingvarsdottir, S.; Gudjonsson, G. I. (Department of Geosciences, The University of Arizona, 2003-01-01)
      The authors present a detailed theoretical and experimental study of the liquid scintillation balanced counting method, widely used in radiocarbon dating, using a simple, laboratory-made system. A fixed counting window becomes a balanced window when the high voltage is set where the 14C count rate rises to a maximum. Using a measured 14C pulse height spectrum, we have calculated the lower and upper limits for 11 balanced windows of varying width and their respective counting efficiencies. Furthermore, we have studied: (1) theoretically and experimentally, the counting efficiency for up to a +/15% shift in pulse height from the balanced setting, (2), the change in pulse height due to temperature variations, (3), the long-time stability of the system, and (4), a method that allows a quick determination of the balance voltage for individual samples, using the Compton spectrum of 133Ba. The standard deviation for thirty 24-hr measuring periods for a 14C standard (190 Bq) was within the expected statistical error (0.03%).
    • Characterizing the Error in the Estimated Age-Depth Relationship

      Solow, Andrew R. (Department of Geosciences, The University of Arizona, 2003-01-01)
      It is common practice to estimate the age of undated material extracted from a sediment core from radiocarbon or other radiometric dates of samples taken above and below the extracted material. This paper presents a simple expression for the variance of this estimated age. This variance accounts for both 14C dating error and error due to bioturbation.
    • Section 4: Investigation of Potential Sources of Variation

      Scott, E. M. (Department of Geosciences, The University of Arizona, 2003-01-01)
    • Section 5: Measures of Precision and Reproducibility

      Scott, E. M. (Department of Geosciences, The University of Arizona, 2003-01-01)
    • Section 7: Characterization of the Reference Materials by Consensus Values

      Scott, E. M. (Department of Geosciences, The University of Arizona, 2003-01-01)
    • Section 8: Optional Further Studies

      Scott, E. M. (Department of Geosciences, The University of Arizona, 2003-01-01)
    • Development of an Automated System for Preparation of Organic Samples

      Hatté, Christine; Poupeau, Jean-Jacques; Tannau, Jean-François; Paterne, Martine (Department of Geosciences, The University of Arizona, 2003-01-01)
      We constructed an automated system to transform organic samples to CO2, which included several options such as: combustion in 2 steps with collection of the 2 fractions, volatile fraction combustion, and 13C sampling. The process includes organic matter combustion, CO2 drying, quantification of the mass of carbon, CO2 collection in a glass vial, and eventually 13C sampling. The system is computer-controlled and-monitored. The apparent background age of the automated system reaches 0.191 +/ 0.011 pMC (2 sigma), equivalent to a 14C age of about 51,700 yr BP, and requires only 30 min of handling, instead of the several days needed when using a manual procedure.
    • Radiocarbon, Volume 45, Number 2 (2003)

      Department of Geosciences, The University of Arizona, 2003-01-01
    • Radiocarbon, Volume 45, Number 1 (2003)

      Department of Geosciences, The University of Arizona, 2003-01-01
    • El Mirón Cave and the 14C Chronology of Cantabrian Spain

      Straus, Lawrence Guy; González Morales, Manuel (Department of Geosciences, The University of Arizona, 2003-01-01)
      Excavations since 1996 in the large El Mirón Cave in the Cantabrian Cordillera of northern Spain have revealed a cultural sequence of late Mousterian, early Upper Paleolithic, Solutrean, Magdalenian, Azilian, Mesolithic, Neolithic, Chalcolithic, Bronze Age, and Medieval occupations. These components have been dated by 51 generally coherent radiocarbon determinations, all run by the Geochron labs, in association with the Lawrence Livermore labs for AMS. This series is one of the largest for a single prehistoric site in Iberia or even Europe. The series is consistent with the record from Cantabrian Spain and provides new detail on the age of the Middle-Upper Paleolithic transition, on the various phases of the Magdalenian culture, on the appearance of the Neolithic in the Atlantic zone of Spain, and on the origins of the socioeconomic complexity in the metal ages. The stratigraphic relationship of 14C-dated levels to a roof-fall block and adjacent cave walls (both with engravings) provides rare terminus post and ante quem ages for execution of the rupestral art in El Mirón during the early to mid Magdalenian. The 14C record has also been instrumental in revealing the existence of depositional hiati during the early Holocene.
    • From the Editor

      Jull, A. J. Timothy (Department of Geosciences, The University of Arizona, 2003-01-01)
    • Is There a Fifth International Radiocarbon Intercomparison (VIRI)?

      Scott, E. M.; Bryant, C.; Cook, G. T.; Naysmith, P. (Department of Geosciences, The University of Arizona, 2003-01-01)
      The issue of comparability of measurements (and thus bias, accuracy, and precision of measurement) from diverse laboratories is one which has been the focus of some attention both within the radiocarbon community and the wider user communities. As a result, the 14C community has undertaken a widescale, far-reaching, and evolving program of inter-comparisons, to the benefit of laboratories and users alike. The benefit to the users is, however, indirect, since the 14C inter-comparisons have not been used to generate "league tables" of performance, but rather to allow individual laboratories to check procedures and modify them as required.
    • Decadal Timescale Shift in the 14C Record of a Central Equatorial Pacific Coral

      Grottoli, A. G.; Gille, S. T.; Druffel, E. R. M.; Dunbar, R. B. (Department of Geosciences, The University of Arizona, 2003-01-01)
      Coral skeletal radiocarbon records reflect seawater Delta-14C and are useful for reconstructing the history of water mass movement and ventilation in the tropical oceans. Here, we reconstructed the inter-annual variability in central equatorial Pacific surface water Delta-14C from 1922-1956 using near-monthly 14C measurements in a Porites sp. Coral skeleton (FI5A) from the windward side of Fanning Island (3 degrees 54'32''N, 159 degrees 18'88''W). The most pronounced feature in this record is a large, positive shift in the Delta-14C between 1947 and 1956 that coincides with the switch of the Pacific Decadal Oscillation (PDO) from a positive to a negative phase in the mid-1940s. Although the absolute Delta-14C values from 1950-1955 in FI5A differ from the Delta-14C values of another coral core collected from the opposite side of the island, both records show a large, positive shift in their Delta-14C records at that time. The relative increase in the Delta-14C of each record is consistent with the premise that a common mechanism is controlling the Delta-14C records within each coral record. Overall, the Fanning Delta-14C data support the notion that a significant amount of subtropical seawater is arriving at the Equator, but does not allow us to determine the mechanism for its transport.
    • Investigation of a Chinese Ink Rubbing by 14C AMS Analysis

      Yuan, Hong-Chien; Kutschera, Walter; Lin, Tze-Yue; Steier, Peter; Vockenhuber, Christof; Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2003-01-01)
      The date of a Chinese ink rubbing was determined using radiocarbon accelerated mass spectrometry (AMS) to be in the range from AD 1480 to AD 1670 (95.4% confidence limit). Together with a scanning electron microscope (SEM) analysis of the ink and a comparative study of the Chinese characters, it was determined that the ink rubbing must have been performed before Emperor Kang Hsi (AD 1662-1772), who ruled at the beginning of the Chin Dynasty. On the other hand, the stone stele, from which the ink rubbing was produced, was carved in AD 531, which is consistent with an analysis of some erased characters. Such analysis seems to be useful to help clarify possible forgeries of these art objects.
    • From the Former Managing Editor

      Elliott, Kim (Department of Geosciences, The University of Arizona, 2003-01-01)
    • Section 6: Kauri Wood, Samples a and B

      Scott, E. M. (Department of Geosciences, The University of Arizona, 2003-01-01)
    • Section 9: Optional Samples

      Scott, E. M. (Department of Geosciences, The University of Arizona, 2003-01-01)