• Validating and Improving Archaeological Phasing at St. Mary Spital, London

      Sidell, Jane; Thomas, Christopher; Baylis, Alex (Department of Geosciences, The University of Arizona, 2007-01-01)
      This paper outlines the radiocarbon program applied to the excavation and skeletal assemblage from the cemetery of the medieval Priory and Hospital of St. Mary Spital in London. Problems encountered in dating medieval cemeteries are outlined. The problems were addressed through the application of Bayesian modeling to validate and refine conventional approaches to constructing phases of archaeological activity. It should be noted that this project was solely funded by the developer of the land; such projects rarely undertake even modest programs of 14C dating. We aim to show how the investment of a proportionally small sum, compared to the overall project costs, may reap significant benefits.
    • Validity of 14C Ages of Carbonates in Sediments

      Chen, Yijian; Polach, Henry (American Journal of Science, 1986-01-01)
      This review is based on geologic surveys carried out in Australia and China as well as on more than 300 14C dates published in Radiocarbon. Evaluated are the origins and pathways of carbonate formation, stable isotopic composition, carbonate nodule growth rates and paleo-climatic effects. The three identified delta-13C abundance peaks are unrelated to environment and carbon source whilst 14C ages group themselves into periods corresponding to past humid warm climate. It is concluded that the major error in caliche dating is due to incorporation of old limestone whilst error on nodule dating is related to their slow growth rate. Thus, caliche antedates and nodules postdate the times of their deposition. delta-13C values cannot be used to correct for limestone or atmospheric contamination effects
    • 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.
    • Variability of Monthly Radiocarbon During the 1760s in Corals from the Galapagos Islands

      Druffel, Ellen R. M.; Griffin, Sheila; Hwang, Jeomshik; Komada, Tomoko; Beaupre, Steven R.; Druffel-Rodriguez, Kevin C.; Santos, Guaciara M.; Southon, John (Department of Geosciences, The University of Arizona, 2004-01-01)
      Radiocarbon (∆14C) measurements of monthly samples from a Galapagos surface coral are among the first data sets from the new Keck Carbon Cycle Accelerator Mass Spectrometry laboratory at the University of California, Irvine. An average ∆14C value of -62 is obtained for 144 measurements of samples from monthly coral bands that lived from about AD 1760-1771 (+/6 yr). High ∆14C values were found during January through March, when upwelling was weak or absent at the Galapagos Islands. Low ∆14C values were obtained mid-year during strong upwelling. The average seasonal variability of ∆14C was 15-25 ppm, which is greater than that at other tropical and subtropical locations in the Pacific Ocean because of intense seasonal upwelling at this site. Periods of sustained high ∆14C values were found during 1762-1763 and 1766. A spectral analysis revealed that the spectral density for the ∆14C data displays most of its variance at the 5-yr cycle, which is reflective of El Niño periodicity during the 20th century.
    • Variation of Concentration, 14C Activity and 13C/12C Ratios of CO2 in Air Samples from Kitt Peak, Arizona

      Leavitt, S. W.; Long, Austin (Department of Geosciences, The University of Arizona, 1989-01-01)
      Air was sampled with 5L flasks at Kitt Peak (2100m elev) from 1983 through 1984 at approximately monthly intervals, occasionally supplemented with air samples from urban Tucson ca 75km away (760m elev). The Kitt Peak CO2 concentrations, represented by a yield measurement, fluctuated ca 25% over the monitoring period. The delta-13C values (uncorrected for N20) varied from ca -7.6 to -9.0%, with high values (and low CO2 yields) in the late summer consistent with hemispheric seasonal biosphere effects. Tucson air has lower delta-13C values and possibly greater CO2 yield suggesting a local fossil-fuel effect. 14C activity of four Kitt Peak samples range from 1.158 +/- .007 to 1.223 +/- .008 as uncorrected fraction of modern, below free air activity of ca 1.250 for 1984 even after correcting for fractionation. The slightly low 14C activity and delta-13C values suggest the Kitt Peak air is not quite 100% clean and there may be a local/regional fossil-fuel contribution, but CO2 concentrations are similar to background atmospheric values.
    • Variation of Radiocarbon Content in Tree Rings During the Maunder Minimum of Solar Activity

      Kocharov, G. E.; Peristykh, A. N.; Kereselidze, P. G.; Lomtatidze, Z. N.; Metskhvarishvili, R. Ya; Tagauri, Z. A.; Tsereteli, S. L.; Zhorzholiani, I. V. (Department of Geosciences, The University of Arizona, 1992-01-01)
      We present here annual data on 14C abundance in tree rings during the Maunder minimum of solar activity (AD 1645–1715). We show that the solar modulation persisted during the minimum. We also compare these data with measurements of 10Be concentration in dated polar ice cores and with records of aurorae recurrence during this time interval.
    • Variation of the Radiocarbon Content in Tree Rings During the Spoerer Minimum

      Miyahara, Hiroko; Masuda, Kimiaki; Furuzawa, Hideki; Menjo, Hiroaki; Muraki, Yasushi; Kitagawa, Hiroyuki; Nakamura Toshio (Department of Geosciences, The University of Arizona, 2004-01-01)
      This paper presents the variation of radiocarbon content in annual tree rings for the period AD 1413-1553, which includes the Spoerer Minimum period (AD 1415-1534). Since the variation of the production rate of 14C is strongly related to solar activity, the variation of 14C content in annual tree rings gives us information on the characteristics of variation of solar activity. We have studied solar activity during the grand solar minima, focusing especially on the stability of the 11-yr cycle. The minima are determined to have been almost free of sunspots. Our results, however, have revealed quite remarkably the existence of the 11-yr cycle for most of the time during the Spoerer Minimum. The 11-yr variation weakened around AD 1460-1510, suggesting that solar activity might have been strongly suppressed during these 50 yr.
    • Variations in 14C Reservoir Ages of Black Sea Waters and Sedimentary Organic Carbon during Anoxic Periods: Influence of Photosynthetic Versus Chemoautotrophic Production

      Fontugne, Michel; Guichard, François; Bentaleb, Ilham; Strechie, Claudia; Lericolais, Gilles (Department of Geosciences, The University of Arizona, 2009-01-01)
      Radiocarbon activity of dissolved inorganic carbon has been measured in the northwestern Black Sea. Both continental shelf and open-sea profiles show that surface waters are in equilibrium with the atmosphere. The observed distribution of 14C activity shows a weak contribution of the deep 14C-depleted CO2 to the photic zone. Such a distribution of 14C within the water column is unable to explain the aging of sedimentary organic matter and reservoir ages greater than 500 yr. A contribution of production by chemoautotrophic bacteria feeding on 14C-depleted methane at the boundary of the oxic and anoxic zones is a realistic hypothesis. Also, a contribution to sedimentary organic carbon estimated at 15% of the photosynthetic primary production could explain 14C reservoir ages greater than 1300 yr.
    • Variations in Radiocarbon Production in the Earth's Atmosphere

      Korf, Serge A.; Mendell, Rosalind B. (American Journal of Science, 1980-01-01)
      We have investigated solar phenomena associated with unusual changes in the production rates of 14C in the atmosphere. 14C is produced in interactions of cosmic ray neutrons with nitrogen in the atmosphere. Intensity of the neutrons varies globally and fluctuates with time as a result of interactions of galactic cosmic rays which generate neutrons with plasma and magnetic fields of the solar wind. We estimate the total mean production rate of 14C for solar cycle 20, specifically 1965 to 1975, to be 2.25 +/- 0.1 nuclei-cm-2sec-1 from galactic cosmic rays alone, with negligible integrated contribution from solar particle events. Annual averages of Rz, the Zurich sunspot number, and the production rate of 14C, n(14C), were related by n(14C) = 2.60 5.53 x 10^(-3) Rz, +/- 3 percent. The contribution of solar flare particles and the zero sunspot limit are discussed with relation to major fluctuations that appear in the radiocarbon versus dendrochronology over short (~100 years) integration times.
    • Variations in the Atmospheric Radiocarbon Concentration Over the Past 1300 Years

      Willis, E. H.; Tauber, H.; Münnich, K. O. (American Journal of Science, 1960-01-01)
    • Variations of 14C in Oats Grown from 1957 to 1978 in Quebec

      Barrette, Louis; La Salle, Pierre; Martel, Yvon; Samson, Claude (American Journal of Science, 1980-01-01)
      Annual atmospheric radiocarbon concentrations for the year 1957 to 1978 are measured through oat seeds grown in the rural region of La Pocatière, Quebec (70 degrees W, 47 degrees N). Results follow the general pattern of other curves obtained from grains elsewhere in the northern hemisphere. Some disagreements suggest a non-uniform mixing process with faster response to stratospheric contamination in definite regions.
    • Variations of Isotopic Composition of Carbon in the Karst Environment from Southern Poland, Present and Past

      Pazdur, Anna; Goslar, Tomasz; Pawlyta, Mirosława; Hercman, Helena; Gradziński, Michał (Department of Geosciences, The University of Arizona, 1999-01-01)
      We describe a comprehensive study of carbon isotopes in several karst springs and their environs in a contemporary karst environment in the region of the Cracow-Wielun Upland and Western Tatra Mountains, Southern Poland. We collected samples of water, plants and carbonate deposited on aquatic plants, and obtained 13C values and 14C concentrations. We also investigated a group of the youngest calcium carbonates from caves where deposition is still being observed or ceased no more than a few hundred years ago. The determination of a 14C dilution factor (q) in these carbonates allows us to determine the "true" radiocarbon ages of old speleothems from caves in the area under investigation and enables the use of old speleothems as suitable material for extending the 14C calibration time scale, the "Absolute" age having been determined by U/Th or amino acid racemization (AAR) dating methods. Measurements of delta-13C and 14C concentrations were made on dissolved inorganic carbon (DIC) extracted from water samples. Calculated values of q range from 0.55 to 0.68 and delta-13C values range from -10 per mil to -13 per mil versus VPDB with mean values equal to 0.65 and -12 per mil, respectively. Results indicate that the dissolution process of limestone bedrock is a closed system with the dominating contributor being biogenic carbon dioxide. Isotopic composition of carbon in contemporary plants collected at the karstic springs at 3 localities is highly diverse, with different species distinctly varying in both q and delta-13C values. Extremely light values of 13C (under -40 per mil), observed in Algae and Hyloconium splendens, are correlated with 14C concentrations that are much lower than 100 pMC. Small systematic changes of isotopic composition were found in plants of the same species collected along streams at various distances from the spring. The youngest calcium carbonates from different caves show a relatively high scatter of both delta-13C values and 14C concentration. The lower reservoir effect for 14C is observed in samples with higher value of delta-13C, indicating equilibrium conditions in the sedimentation of carbonate. Pazdur et al. (1995b) presented 14C dating results and paleoclimatic interpretation of 170 14C analyses of 89 speleothems from 41 caves obtained through 1994. Investigations continued until early 1997, during which time a speleothem, JWi2, was dated by 14C, U/Th and AAR dating methods, and its stable isotope composition (delta-13C and delta-18O) analyzed in detail (reported here). Carbon isotope analyses indicate very large differences among results obtained by U/Th, AAR, and 14C dating methods.
    • Variations of Radiocarbon in Tree Rings: Southern Hemisphere Offset Preliminary Results

      McCormac, F. G.; Hogg, A. G.; Higham, T. G.; Baillie, M. L.; Palmer, J. G.; Xiong, Limin; Pilcher, J. R.; Brown, David; Hoper, S. T. (Department of Geosciences, The University of Arizona, 1998-01-01)
      The Queen's University of Belfast, Northern Ireland and University of Waikato, Hamilton, New Zealand radiocarbon laboratories have undertaken a series of high-precision measurements on decadal samples of dendrochronologically dated oak (Quercus patrea) and cedar (Libocedrus bidwillii) from Great Britain and New Zealand, respectively. The results show a real atmospheric offset of 3.4 +/0.6% (27.2 +/4.7 14C yr) between the two locations for the interval AD 1725 to AD 1885, with the Southern Hemisphere being depleted in 4C. This result is less than the value currently used to correct Southern Hemisphere calibrations, possibly indicating a gradient in Delta-14C within the Southern Hemisphere.
    • Verification of an Archaic Age Occupation on Barbados, Southern Lesser Antilles

      Fitzpatrick, Scott M. (Department of Geosciences, The University of Arizona, 2011-12-16)
      The Caribbean Archaic Age (about 3000–500 BC) is thought to represent the earliest migration of humans from South America into the Lesser Antilles. However, here is a conspicuous absence of these early sites on islands south of the Guadeloupe Passage. To date, only a single radiocarbon date derived from a Queen conch (Strombus [Eustrombus] gigas) shell at the Heywoods site on Barbados was indicative of an Archaic occupation in the southern Antilles apart from a scattering of poorly reported (and mostly undated) sites. Given a number of issues associated with reliance on a single date to establish a cultural horizon, along with other problems derived from possible carbonate cement contamination and dating marine shells of a longer-lived species such as Queen conch, 2 additional samples were taken from the same unit and context at Heywoods to confirm whether the site is truly representative of an occupation during the Archaic Age. Results from a Queen conch shell adze in Context 7 dated to 2530–2200 BC (2 sigma) and overlaps with the only other Archaic date from the site dating to 2320–1750 cal BC, while a juvenile specimen of the same species from Context 8 at 3280–2940 BC (2 sigma) indicates that Barbados may have been settled even earlier. This suggests that Heywoods may be the oldest site between Trinidad and Puerto Rico. While further confirmation is required, these new dates have implications for understanding the nature of migratory ventures in the Caribbean, such as whether the Southward Route hypothesis which postulates that earlier migration events from South America during the Ceramic Age (beginning ~500 BC) initially bypassed the southern Lesser Antilles also applies to the Archaic, and if other phenomena such as active volcanism may have played a role in structuring settlement patterns. Questions also remain as to why Heywoods does not exhibit the typical lithic Archaic tool kit.
    • Vertical Advection—Diffusion Rates in the Oceanic Thermocline Determined from 14C Distributions

      Quay, P. D.; Stuiver, Minze (American Journal of Science, 1980-01-01)
      The characteristics of a one-dimensional vertical advection-diffusion ocean mixing model were examined using temperature, salinity, and bomb 14C measurements made during the GEOSECS program. Vertical advection (W) and eddy diffusion (K) rates for the main oceanic thermocliine and CO2 gas exchange rates (E) were determined from the depth distributions of salinity and bomb produced 14C measured in the upper 1000m of the Atlantic and Pacific Oceans. In the Atlantic, the results suggest that vertical diffusion rates are lower in the equatorial region (K = 0.6cm2sec-1) than in the temperate region (K = 1.6cm2sec-1). Upwelling rates were calculated for stations located between about 30 degrees N and 30 degrees S and average 10m yr-1, corresponding to an upward transport of about 10 Sverdrups. Model calculations of the gas exchange rate of CO2 indicate a 2 to 3-fold decrease between temperate latitudes and the equatorial latitudes of the Atlantic. For many of the Pacific GEOSECS stations, the Delta-14C depth distribution is distinctly different than in the Atlantic, and cannot be used to calculate unique values of K and W that explain both the salinity and 14C depth distributions.
    • Very Long-Lived Mollusks Confirm 17th Century AD Tephra-Based Radiocarbon Reservoir Ages for North Icelandic Shelf Waters

      Wanamaker, Alan D., Jr.; Heinemeier, Jan; Scourse, James D.; Richardson, Christopher A.; Butler, Paul G.; Eiríksson, Jon; Knudsen, Karen Luise (Department of Geosciences, The University of Arizona, 2008-01-01)
      Marine sediment records from the north Icelandic shelf, which rely on tephrochronological age models, reveal an average Delta-R (regional deviation from the modeled global surface ocean reservoir age) of approximately 150 yr for the last millennium. These tephra-based age models have not hitherto been independently verified. Here, we provide data that corroborate Delta-R values derived from these sediment archives. We sampled the youngest portion (ontogenetic age) of a bivalve shell, Arctica islandica (L.), for radiocarbon analysis, which was collected alive in 2006 from the north Icelandic shelf in ~80 m water depth. Annual band counting from the sectioned shell revealed that this clam lived for more than 405 yr, making it the longest-lived mollusk and possibly the oldest non-colonial animal yet documented. The 14C age derived from the umbo region of the shell is 951 +/- 27 yr BP. Assuming that the bivalve settled onto the seabed at AD 1600, the corresponding local value of Delta-R is found to be 237 +/- 35 yr by comparison of the 14C age with the Marine04 calibration curve (Hughen et al. 2004) at this time. Furthermore, we cross-matched a 287-yr-old, dead-collected, A. islandica shell from AD 1601 to 1656 from the same site with the live-caught individual. 14C analysis from the ventral margin of this shell revealed a Delta-R of 186 +/- 50 yr at AD 1650. These values compare favorably with each other and with the tephra-based Delta-R values during this period, illustrating that 14C from A. islandica can effectively record 14C reservoir changes in the shelf seas.
    • Victoria Natural Radiocarbon Measurements I

      Bermingham, Anne (American Journal of Science, 1966-01-01)
    • Vienna Radium Institute Radiocarbon Dates I

      Felber, Heinz (American Journal of Science, 1969-12-31)
    • Vienna Radium Institute Radiocarbon Dates II

      Felber, Heinz (American Journal of Science, 1970-12-31)
    • Vienna Radium Institute Radiocarbon Dates III

      Felber, Heinz; Pak, Edwin (American Journal of Science, 1972-01-01)