• Calibrated 14C Dates in Central Europe - Same as Elsewhere?

      Freundlich, J. C.; Schmidt, Burghart (American Journal of Science, 1983-01-01)
      14C dating results derived from an absolutely-dated 471-year tree-ring sequence from central European oak show a trend towards somewhat older dates than those for bristlecone pine tree rings of the same age, but similar to those for Egyptian historical samples. Differences visible between these trend lines are not relevant considering the standard errors proposed by Clark (1975).
    • Current 14C Measurements with the University of Washington Accelerator Facility for Radioisotope Dating

      Farwell, G. W.; Grootes, P. M.; Leach, D. D.; Schmidt, F. H.; Stuiver, Minze (American Journal of Science, 1983-01-01)
      Our accelerator mass spectrometry (AMS) system shows a one-to-one relationship between sample 14C concentrations determined by AMS and by Beta-counting. Measurements of unknown samples against a standard indicate that 14C concentration measurements to better than 2% can be made. For a 30-second data collection interval in a typical run of 100 intervals, the variability of the beam injected into the accelerator is ca 2%, that of the machine transmission is ca 4%, and counting statistics give 4.7% standard deviation for a sample of 80% of modern carbon.
    • Dendrochronology at Belfast as a Background to High-Precision Calibration

      Baillie, M. G. L.; Pilcher, J. R.; Pearson, G. W. (American Journal of Science, 1983-01-01)
    • Dendrochronology of Bristlecone Pine: A Progress Report

      Ferguson, C. W.; Graybill, D. A. (American Journal of Science, 1983-01-01)
      Dendrochronological studies of bristlecone pine, Pinus longaeva, have produced a continuous tree-ring sequence back to 6700 BC for the White Mountains of California and to 3258 BC for east-central Nevada.
    • On a 50-Year "Climate-Free" delta-13C Record from Juniper Tree Rings

      Leavitt, Steven W.; Long, Austin (American Journal of Science, 1983-01-01)
    • Possible Depletion in 14C in Trees Growing in Calcareous Soils

      Tauber, Henrik (American Journal of Science, 1983-01-01)
      14C activities of decadal samples from beech trees growing under extreme calcareous conditions were compared to 14C activities of decadal samples of the same age from a beech tree growing in a normal mold soil in order to see whether part of the carbon assimilated during photosynthesis might originate from 14C-deficient carbonates in the soil. The calcareous soils contained from 18 to 52% calcium carbonate, and this carbonate had a mean 14C age of 10,200 to 17,600 years BP. A comparison was also made with the 14C activity of contemporaneous samples from Douglas Fir from the US North Pacific (Stuiver, 1982). No significant depletion in 14C activity in beech trees growing in the highly calcareous soils was detected. The measured mean difference in 14C activity in beech trees from calcareous and non-calcareous sites corresponds to an uptake of 0.12 +/- 0.3% carbon from soil carbonates in the calcareous sites.
    • Radiocarbon Activity Variation in Dated Tree Rings Grown in Mackenzie Delta

      Fan, C. Y.; Tie-Mei, Chen; Si-Xun, Yun; Kai-Mei, Dai (American Journal of Science, 1983-01-01)
      Forty-five tree rings (1881-1925) were taken from a white spruce grown near Campbell River in Mackenzie Delta, Canada, for the measurement of 14C activity variation. Because of the narrowness of the rings, 2 and sometimes 3 rings were combined to yield a total of 21 specimens. The 14C content in these specimens was measured with a liquid scintillation-PM tube counter system of the History Department of Peking University. The data points exhibit a 10 per mil variation, anti-correlated with sunspot numbers. The physical implication is discussed.
    • Results of Tests and Measurements from the NSF Regional Accelerator Facility for Radioisotope Dating

      Donahue, D. J.; Zabel, T. H.; Jull, A. J. T.; Damon, P. E.; Purser, K. H. (American Journal of Science, 1983-01-01)
      Tests of performance of the tandem accelerator mass spectrometer at the NSF Regional Facility at the University of Arizona are discussed. Results of measurements on some tree rings and on some archaeologic samples are presented.
    • Short-Term Variations in Radiocarbon Concentration with the 11-Year Solar Cycle

      Povinec, Pavel; Burchuladze, A. A.; Pagava, S. V. (American Journal of Science, 1983-01-01)
      Previous investigations on short-term 14C variations in tree rings are compared with 14C measurements in wine samples. The comparison is made for 4 solar cycles (1903-1944) with the same method of statistical evaluation of measured results. The average amplitude of Delta-14 variations as observed by various authors in tree-ring samples is ca 2 +/1 per mil; however, wine samples show an average amplitude of 4.3 +/1.6 per mil. The anticorrelation dependence of Delta-14C on Wolf sunspot numbers was observed with a time shift between W maxima and Delta-14C minima of 3-5 yr for different solar cycles.
    • Statistics of the AD Record of Climatic and Carbon Isotopic Change

      Stuiver, Minze (American Journal of Science, 1983-01-01)
      The AD time series of Delta-14C, delta-13C, and cosmic ray fluxes, Q, were analyzed for similarities. Two cases of significant correlation between Q and tree-ring delta-13C were encountered, for which up to 25% of the variance can be attributed to changes in the tree's isotope fractionation that related to solar induced climatic changes. However, it is possible that the demonstrated correlation is fortuitous because actual climate proxy records generally do not correlate significantly with the Q record.