• A 14C Calibration with AMS from 3500 to 3000 BC, Derived from a New High-Elevation Stone-Pine Tree-Ring Chronology

      Dellinger, Franz; Kutschera, Walter; Nicolussi, Kurt; Schießling, Peter; Steier, Peter; Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2004-01-01)
      High-precision radiocarbon accelerator mass spectrometry (AMS) measurements of a new high-altitude stone-pine tree-ring chronology from the European Alps were performed for a 500-yr stretch in the second half of the 4th millennium BC. A 14C calibration curve with a typical 1-sigma uncertainty of about 20 14C yr was achieved. Although the general agreement of our data set with INTCAL98 is very good (confirming once more that INTCAL98 is also proper for calibration of samples of extraordinary sites), we found small deviations of 17 +/5 14C yr, indicating possible seasonal effects of the delayed growing season at high altitude.
    • A 14C Electronic Measurement System with a Microcomputer

      Walanus, Adam (American Journal of Science, 1986-01-01)
      Even though the reliability of equipment has improved, the quality of measurement should still be checked. This task may be performed by a microcomputer with the physicist's intervention only when an error in measurement is detected.
    • 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.
    • A 30,000-Year Pollen and Radiocarbon Record from Highland Sumatra as Evidence for Climatic Change

      Maloney, B. K.; McCormac, F. G. (Department of Geosciences, The University of Arizona, 1995-01-01)
      We examine the pollen analytical and 14C sequences from two Sumatra highland sites, Pea Bullok (2 degrees 15'N, 99 degrees 02'E) and Danau di-Atas (1 degree 04'S, 100 degrees 46'E). The pollen diagrams do not correlate particularly well, possibly because two of the samples from Danau di-Atas analyzed by radioactive decay counting earlier should be infinite. Other complications are differences in the type of site, local topography, pollen sums used and difficulty in distinguishing between pollen taxa from local and regional vegetation. The older material from Pea Bullok was AMS dated.
    • A 36Cl Profile in Greenland Ice from AD 1265 to 1865

      Conard, N. J.; Gove, H. E.; Elmore, David (Department of Geosciences, The University of Arizona, 1989-01-01)
      We have measured the concentration of 36Cl in 67 samples from the upper portion of the Camp Century ice core. The profile extends from AD 1265 to 1865 and covers the times of the Wolf (AD 1282-1342), Spoerer (AD 1416-1534) and Maunder (AD 1645-1715) minima in sunspot number. Although the profile exhibits much short-term variation, a smoothed plot of the data shows a strong peak in 36Cl concentration over the time of the Maunder Minimum. The deeper part of the core suggests increased deposition of 36Cl over the periods of the Wolf and Spoerer minima. The time resolution of the profile is inadequate for testing for an 11-year periodicity in our data. The data augment evidence from 10Be and 14C studies which indicate solar modulation of radioisotope production. Since, however, much of the short-term variation of 36Cl seems to be independent of solar activity, other factors must affect the deposition of 36Cl in ice. These variations could be due in part to mechanisms affecting the transport of 36Cl in the atmosphere. Based on our data from Camp Century, we calculate an average input of 36Cl of 24 atoms/m2 sec.
    • A 40,000-Year Varve Chronology from Lake Suigetsu, Japan: Extension of the 14C Calibration Curve

      Kitagawa, Hiroyuki; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 1998-01-01)
      A sequence of annually laminated sediments is a potential tool for calibrating the radiocarbon time scale beyond the range of the absolute tree-ring calibration (11 ka). We performed accelerator mass spectrometric (AMS) 14C measurements on >250 terrestrial macrofossil samples from a 40,000-yr varve sequence from Lake Suigetsu, Japan. The results yield the first calibration curve for the total range of the 14C dating method.
    • A Batch Preparation Method for Graphite Targets with Low Background for AMS 14C Measurements

      Kitagawa, Hiroyuki; Masazawa, Toshiyuki; Nakamura, Toshio; Matsumoto, Eiji (Department of Geosciences, The University of Arizona, 1993-01-01)
      We have developed a method of graphitization from CO2 samples for accurate 14C measurements by accelerator mass spectrometry. Our batch method, using a sealed Vycor tube, reduces the risk of contamination during graphitization and makes it possible to prepare many samples in a short time (typically 20 samples per day).
    • A Bayesian Approach to the Estimation of Radiocarbon Calibration Curves: The IntCal09 Methodology

      Heaton, T. J.; Blackwell, P. G.; Buck, C. E. (Department of Geosciences, The University of Arizona, 2009-01-01)
      This article presents a new approach to the construction of radiocarbon calibration curves. The Bayesian methodology was developed specifically to facilitate construction of the 2009 updates to the internationally agreed 14C calibration curves known as IntCal09 and Marine09. The curve estimation approach taken uses Markov chain Monte Carlo sampling, specifically a Metropolis-within-Gibbs sampler, which offers improved flexibility and reliability over the approaches used in the past. In particular, the method allows accurate modeling of calibration data with 14C determinations that arise from material deposited over several consecutive calendar years and that exhibit complex uncertainty structures on their calendar date estimates (arising from methods such as wiggle-matching and varve counting).
    • A Bayesian Approach to the Use of 14C Dates in the Estimation of the Age of Peat

      Christen, J. A.; Clymo, R. S.; Litton, C. D. (Department of Geosciences, The University of Arizona, 1995-01-01)
      Peatlands occupy a significant portion of the land surface of the Earth and form a large carbon store. Most peat-forming systems have two layers. The upper layer, the acrotelm, fixes carbon by photosynthesis, loses some of it by decay and passes the remainder on to the lower layer, the catotelm. In the catotelm, decay continues at a slower rate. Mathematical models of the growth of the catotelm have been proposed which relate the cumulative mass of peat above a particular depth to calendar age of the peat at that depth. We demonstrate how 14C dating and the Bayesian approach to data analysis can be used to make inferences about the relation between calendar age and cumulative mass, and to estimate the accumulation and decay rates.
    • A Bayesian Framework for Age Modeling of Radiocarbon-Dated Peat Deposits: Case Studies from the Netherlands

      Blaauw, Maarten; Bakker, Ronald; Christen, J. Andrés; Hall, Valerie A.; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 2007-01-01)
      Recently, Bayesian statistical software has been developed for age-depth modeling (wiggle-match dating) of sequences of densely spaced radiocarbon dates from peat cores. The method is described in non-statistical terms, and is compared with an alternative method of chronological ordering of 14C dates. Case studies include the dating of the start of agriculture in the northeastern part of the Netherlands, and of a possible Hekla-3 tephra layer in the same country. We discuss future enhancements in Bayesian age modeling.
    • A Bayesian Re-Assessment of the Earliest Radiocarbon Dates from Tiwanaku, Bolivia

      Marsh, Erik J. (Department of Geosciences, The University of Arizona, 2012-08-17)
      The development of sociopolitical complexity at Tiwanaku around AD 500 was one of the major episodes of social change in the history of the Lake Titicaca Basin. It was the result of poorly understood processes that took place at a series of ceremonial centers in the preceding centuries. The history of Tiwanaku during this time is especially unclear, because the only radiocarbon dates are from excavations whose details were never completely published. Despite this, there is consensus that Tiwanaku was founded around 300 BC. A re-evaluation of the archaeological context of each of these dates shows many of them to be unreliable. Two Bayesian models from independent excavations agree that Tiwanaku was in fact founded centuries later, most likely around AD 110 (50–170, 1σ). This has important implications for widely used monolith and ceramic sequences, as well as understanding the rise of Tiwanaku and other archaic states.
    • A Beam Profile Monitor for Rare Isotopes in Accelerator Mass Spectrometry: Preliminary Measurements

      Taccetti, F.; Carraresi, L.; Fedi, M. E.; Manetti, M.; Mariani, P.; Tobia, G.; Mandò, P. A. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In accelerator systems, beam lines are generally equipped with diagnostic elements, such as Faraday cups and beam profile monitors (BPM), to optimize beam transport. These diagnostic elements, or at least commercial ones, are designed to only work with continuous beams, and their typical maximum sensitivity is about few tens of pA. Thus, in the case of diagnosis of rare isotope beams in accelerator mass spectrometry (AMS), Faraday cups and BPMs are not suitable on the high-energy side of the tandem accelerator, after energy-mass-charge analysis. For example, in 14C AMS, even for a modern sample, the expected counting rate is a few tens of Hz; in these conditions, a commercial BPM cannot be used. On the other hand, checking the shape and the position of the rare isotope beam hitting the detector can be important in order to better identify signals in the detector itself, thus also helping in reducing the measurement background. This paper presents a prototype BPM especially designed for low-intensity beams. The BPM is based on a multiwire proportional chamber characterized by 2 grids of anode wires, oriented perpendicular to each other in order to measure both the x and the y coordinates of the particle impact point. Details about the design and the electronics of the device are given, and the first test measurements are discussed.
    • A Beta Test Comparison Between the New Packard 2260 XL and the LKB Quantulus and 1219 SM: Low-Level Radiocarbon and Tritium Determinations

      Kalin, Robert M. (Department of Geosciences, The University of Arizona, 1989-01-01)
      A Packard 2260 XL liquid scintillation counter was placed in an underground counting chamber to test performance under immense physical shielding. Results from the Packard 2260 XL are compared with two other counters under the same conditions, the LKB Quantulus, which has operated for two years in this laboratory, and the LKB 1219 SM, in use since January 1988.
    • A Beta-Counting System Linked to a Personal Computer

      Omoto, Kunio (Department of Geosciences, The University of Arizona, 1995-01-01)
      The automatic beta-counting system plays a significant role in obtaining high-level reproducibility and reliability in conventional radiocarbon dating. I review here the results achieved by using the "Fully Automatic Radiocarbon Dating System" developed by Omoto (1982). Since setting up the system in 1981, I was able not only to save operator time in beta counting, but also to obtain accurate dates with only minimal uncertainties. Another positive result was the introduction of the automatic voltage correction program, which produced excellent results for counting sample materials over a long period.
    • A Bibliography of Radiocarbon Dating

      Johnson, Frederick (American Journal of Science, 1959-01-01)
    • A Chronological Guide to International Radiocarbon Conferences

      Department of Geosciences, The University of Arizona, 1989-01-01
    • A Chronological Guide to International Radiocarbon Conferences and Publications

      Department of Geosciences, The University of Arizona, 1995-01-01
      A Chronological Guide to International Radiocarbon Conferences and Publications
    • A Chronology of the Pre-Columbian Paracas and Nasca Cultures in South Peru Based on AMS 14C Dating

      Unkel, Ingmar; Kromer, Bernd; Reindel, Markus; Wacker, Lukas; Wagner, Günther (Department of Geosciences, The University of Arizona, 2007-01-01)
      The people of the Paracas and Nasca cultures, the creators of the famous geoglyphs, lived in the desert of the southern coast of Peru between about 800 BC and AD 650. The archaeological chronology of these cultures has been based almost exclusively on a sequence of ceramic styles. The absolute dating of some of the style phases was supported by a few radiocarbon dates (Rowe 1967). Here, we present an absolute chronology of the Paracas and Nasca cultures based on 14C dating of more than 100 organic samples from settlement and tomb relics, as well as on material derived from geoglyph sites in the Nasca/Palpa region (south Peru). The main focus has been on Nasca period settlement centers near Palpa, Los Molinos and La Mua, the Paracas period site of Jauranga, and the Initial period site of Pernil Alto. Most of the 14C samples were dated at the accelerator mass spectrometry (AMS) facility of the ETH Zurich (Switzerland). The targets were produced in the newly built graphitization line at the Heidelberg 14C laboratory (Germany). Clay (adobe) bricks, which are quite a common building material in Peru, were successfully tested to be used for AMS 14C dating of adobe architecture in Peruvian archaeology.
    • A Chronology of the Scythian Antiquities of Eurasia Based On New Archaeological and 14C Data

      Alekseev, A. Yu.; Bokovenko, N. A.; Boltrik, Yu; Chugunov, K. A.; Cook, G.; Dergachev, V. A.; Kovalyukh, N.; Possnert, G.; van der Plicht, J.; Scott, E. M.; et al. (Department of Geosciences, The University of Arizona, 2001-01-01)
      The paper is compares the chronology of the monuments of the Scythian epoch located in the east and west of the Eurasian steppe zone on the basis of both archaeological and radiocarbon data. The lists of 14C dates for the monuments located in different parts of Eurasia are presented according to the periods of their existence. Generally, the 14C dates are confirmed the archaeological point of view and allow us to compare the chronological position of the European and Asian Scythian monuments on the united 14C time scale.
    • A Comparative Study of Monsoonal and Non-Monsoonal Himalayan Lakes, India

      Kusumgar, Sheela; Agrawal, D. P.; Deshpande, R. D.; Ramesh, Rengaswamy; Sharma, C.; Yadava, M. G. (Department of Geosciences, The University of Arizona, 1995-01-01)
      Sedimentological, mineral magnetic and carbon isotopic studies on cores from Mansar Lake in the Jammu area provide paleomonsoonal history dating back to 580 BC. From ca. 580 BC to AD 300, the region experienced precipitation similar to the present, whereas from AD 300 to 1400, the monsoon was relatively subdued. A small excursion ca. AD 1100 suggests an effect of medieval warming. Studies in the Kumaon region did not provide a proper precipitation record, as anthropogenic activity interfered with sedimentation. Manasbal Lake in Kashmir gave an inversion of 14C chronology due to younger paleosols in the drainage basin. Further, the episodic nature of sedimentation in Manasbal Lake hampered the reconstruction of precipitation history in the area.