• A Delta-R Correction Value for Samoa from Known-Age Marine Shells

      Phelan, Matthew B. (Department of Geosciences, The University of Arizona, 1999-01-01)
      A first-order Delta-R correction value for marine samples is presented based on 3 radiocarbon determinations of known-age marine shells from Samoa.
    • Subject Index Volume 41, 1999

      Department of Geosciences, The University of Arizona, 1999-01-01
    • Reporting 14C Activities and Concentrations

      Mook, Willem G.; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 1999-01-01)
      Three modes of reporting 14C activities are in use, in part analogous to the internationally accepted (IAEA) conventions for stable isotopes: (1) absolute activity, the specific activity of 14C or the activity per gram of carbon; (2) activity ratio, the ratio between the absolute activities of a sample and the standard; and (3) relative activity, the difference between the absolute activities of a sample and standard material, relative to the absolute standard activity. The basic definitions originate from decisions made by the radiocarbon community at its past conferences. Stuiver and Polach (1977) reviewed and sought to specify the definitions and conventions. Several colleagues, however, have experienced inadequacies and pitfalls in the definitions and use of symbols. Furthermore, the latter have to be slightly amended because of the use of modern measuring techniques. This paper is intended to provide a consistent set of reporting symbols and definitions, illustrated by some practical examples.
    • Ede Hertelendi (1950-1999)

      Svingor, Éva (Department of Geosciences, The University of Arizona, 1999-01-01)
    • Radiocarbon Laboratories

      Department of Geosciences, The University of Arizona, 1999-01-01
    • Associate Editors

      Department of Geosciences, The University of Arizona, 1999-01-01
    • A 23-Year Retrospective Blind Check of Accuracy of the Copenhagen Radiocarbon Dating System

      Rasmussen, Kaare L.; Tauber, Henrik; Bonde, Niels; Christensen, Kjeld; Theodórsson, Páll (Department of Geosciences, The University of Arizona, 1999-01-01)
      A 23-yr record of the measuring accuracy of the Copenhagen radiocarbon dating laboratory has retrospectively been provided through a true blind test. A total of 92 samples of oak from old tree trunks were dated in the period 1971 to 1993 and their dendrochronological age determined independently. The 14C activity of the dendrochronological samples measured in the Copenhagen radiocarbon laboratory was compared to the activity of the tree rings of the same age measured by Stuiver and Pearson (1993) for calibration purposes. The average difference was found to be 54 +/72 14C yr. The results further indicate that the actual standard deviation is only 7% higher than that quoted by the laboratory. The investigation has shown a long-term stability of laboratory accuracy with no systematic laboratory variations either with respect to sample age or to the time of measurement from 1971 to 1993.
    • Radiocarbon, Volume 41, Number 1 (1999)

      Department of Geosciences, The University of Arizona, 1999-01-01
    • Radiocarbon Dates from Northern Mongolia

      Hall, Mark; Batsaikhan, Zagd; Honeychurch, William (Department of Geosciences, The University of Arizona, 1999-01-01)
      Since 1996, the Mongolian-American Expedition to Northern Mongolia has been excavating in the Egiin Gol Valley. The goal of this research has been to examine the competing hypotheses explaining the emergence of pastoral nomadism and the evolution of nomadic complexity. The chronological placement of burials and sites in the survey area has been a key facet of this research. At present, these investigations have generated 10 radiocarbon dates from archaeological contexts. Presented here are the previously unpublished 14C dates and some comments on their significance.
    • Editorial Board

      Department of Geosciences, The University of Arizona, 1999-01-01
    • Calculation of Past Dead Carbon Proportion and Variability by the Comparison of AMS 14C and TIMS U/Th Ages on Two Holocene Stalagmites

      Genty, Dominique; Massault, Marc; Gilmour, Mabs; Baker, Andy; Verheyden, Sophie; Keppens, Eddy (Department of Geosciences, The University of Arizona, 1999-01-01)
      Twenty-two radiocarbon activity measurements were made by accelerator mass spectrometry (AMS) on 2 Holocene stalagmites from Belgium (Han-stm lb) and from southwest France (Vil-stm lb). Sixteen thermal ionization mass spectrometric (TIMS) U/Th measurements were performed parallel to AMS analyses. The past dead carbon proportion (dcp) due to limestone dissolution and old soil organic matter (SOM) degradation is calculated with U/Th ages, measured calcite 14C activity and atmospheric 14C activity from the dendrochronological calibration curves. Results show that the dcp is different for the 2 stalagmites: between 10,800 and 4780 yr from present dcp = 17.5% (sigma = 2.4; n = 10) for Han-stm lb and dcp = 9.4% (sigma = 1.6; n = 6) between 3070 and 520 yr for Vil-stmlb. Despite a broad stability of the dcp during the time ranges covered by each sample, a slight dcp increase of about 5.0% is observed in the Han-stmlb sample between 8500 and 5200 yr. This change is synchronous with a calcite delta-13C increase, which could be due to variation in limestone dissolution processes possibly linked with a vegetation change. The dcp and delta-13C of the 2 studied samples are compared with 5 other modern stalagmites from Europe. Results show that several factors intervene, among them: the vegetation type, and the soil saturation leading to variable dissolution process systems (open/closed). The good correlation (R2 = 0.98) between the U/Th ages and the calibrated 14C ages corrected with a constant dcp validates the 14C method. However, the dcp error leads to large 14C age errors (i.e. 250-500 yr for the period studied), which is an obstacle for both a high-resolution chronology and the improvement of the 14C calibration curves, at least for the Holocene.
    • Reliability of Bone Gelatin AMS Dating: Rattus exulans and Marine Shell Radiocarbon Dates from Pauatahanui Midden Sites in Wellington, New Zealand

      Athfield, Nancy Beavan; McFadgen, Bruce; Sparks, Rodger (Department of Geosciences, The University of Arizona, 1999-01-01)
      A suite of 6 bone gelatin accelerator mass spectrometry (AMS) radiocarbon dates for Rattus exulans Peale and associated beta decay 14C dates for Austrovenus stutchburyi shell are presented for 4 middens at Pauatahanui, Wellington, New Zealand. Mean calibrated age ranges of Rattus exulans (520-435 BP and 350-330 BP at 95% confidence level) and shell (465-375 BP at 95% confidence level) from the 4 midden sites overlap. The agreement between Rattus exulans bone gelatin dates and associated shell provides an inter-sample comparison of 14C dating using both gas counting (beta decay) and AMS dating techniques. We examine the adequacy of the standard gelatinization treatment for bone samples, which has been employed consistently at the laboratory since 1995.
    • Radiocarbon Updates

      Department of Geosciences, The University of Arizona, 1999-01-01
    • Radiocarbon Age Anomalies in Land Snail Shells from Texas: Ontogenetic, Individual, and Geographic Patterns of Variation

      Goodfriend, Glenn A.; Ellis, G. Lain; Toolin, L. J. (Department of Geosciences, The University of Arizona, 1999-01-01)
      Accelerator mass spectrometric (AMS) radiocarbon analyses of live-collected, prebomb samples of shell carbonates of the land snails Rabdotus dealbatus and R. Alternatus from Texas were carried out to quantify the characteristic age anomalies of land snails from limestone areas. Age anomalies are similar for the two species; they average +700 yr and vary by +/180 yr (1 sigma) among samples. Serial analysis of 1 shell reveals a significant ontogenetic trend in 14C age anomalies, with older apparent ages (up to 1200 yr) in the apical part of the shell and younger and uniform ages in the last whorl. No trend in age anomalies was found across a broad range of rainfall conditions (from 300 to 1000 mm mean annual rainfall).
    • Radiocarbon Distribution in Northwest Belarus Near the Ignalina Nuclear Power Plant

      Mikhajlov, Nikolaj D.; Kolkovsky, Vladimir M.; Pavlova, Iren D. (Department of Geosciences, The University of Arizona, 1999-01-01)
      Since 1994, the Institute of Geological Sciences has undertaken an environmental monitoring program to measure radiocarbon levels in territory adjacent to active nuclear power plants (NPP). We determined 14C concentrations in natural objects from areas contiguous to Ignalina NPP as well as 14C background concentration in areas remote from the NPP. In the environs of the Ignalina station comparatively elevated levels of 14C were observed in vegetation and waters of Lake Drisvyaty. This appears to be a consequence of release of carbon radioisotope into the atmosphere and probably into waters of the lake during operation of the nuclear reactor.
    • Book Review: From Hiroshima to the Iceman: The Development and Applications of Accelerator Mass Spectrometry, Harry E. Gove

      Kutschera, Walter (Department of Geosciences, The University of Arizona, 1999-01-01)
    • From the Editor

      Jull, A. J. T. (Department of Geosciences, The University of Arizona, 1999-01-01)
    • Author Index Volume 41, 1999

      Department of Geosciences, The University of Arizona, 1999-01-01
    • From the Editor

      Long, Austin (Department of Geosciences, The University of Arizona, 1999-01-01)