• Radiocarbon Calibration by Means of Mass Spectrometric 230Th/234U and 14C Ages of Corals: An Updated Database Including Samples from Barbados, Mururoa and Tahiti

      Bard, Edouard; Arnold, Maurice; Hamelin, Bruno; Tisnérat-Laborde, Nadine; Cabioch, Guy (Department of Geosciences, The University of Arizona, 1998-01-01)
      As first shown by Bard et al. (1990a), high-precision 230Th-234U ages can be used successfully to calibrate the radiocarbon time scale beyond the high-precision tree-ring calibration that now reaches 11,900 cal BP (Kromer and Spurk 1998). Using mass spectrometric techniques, we measured 14C and 230Th ages on new samples collected from boreholes drilled off the islands of Tahiti and Mururoa (French Polynesia) in order to complement the database previously obtained on Barbados corals (Bard et al. 1990a, 1993).
    • Radiocarbon Updates

      Department of Geosciences, The University of Arizona, 1998-01-01
    • Radiocarbon, Volume 40, Number 3 (INTCAL 98: Calibration Issue, 1998)

      Department of Geosciences, The University of Arizona, 1998-01-01
    • Revision and Tentative Extension of the Tree-Ring Based 14C Calibration, 9200-11,855 cal BP

      Kromer, Bernd; Spurk, Marco (Department of Geosciences, The University of Arizona, 1998-01-01)
      We report radiocarbon calibration data based on the revised German oak and pine series. The age range of the absolutely dated German oak series has been extended to 10,430 cal BP. The German pine series is tentatively linked to the oak series by 14C, and now reaches back to 11,871 cal BP (+/20 yr). The revisions of the tree-ring time scale of the German oak chronology solved long-standing apparent discrepancies in the mid-Holocene 14C calibration data sets. The calibration data set based on the floating German pine is now in close agreement with the Preboreal part of 14C calibration series obtained from most varve chronologies and corals.
    • Revisions and Extension of the Hohenheim Oak and Pine Chronologies: New Evidence About the Timing of the Younger Dryas/Preboreal Transition

      Spurk, Marco; Friedrich, Michael; Hofmann, Jutta; Remmele, Sabine; Frenzel, Burkhard; Leuschner, Hanns Hubert; Kromer, Bernd (Department of Geosciences, The University of Arizona, 1998-01-01)
      Oak and pine samples housed at the Institute of Botany, University of Hohenheim, are the backbone of the early Holocene part of the radiocarbon calibration curve, published in 1993 (Becker 1993; Kromer and Becker 1993; Stuiver and Becker 1993; Vogel et al. 1993). Since then the chronologies have been revised. The revisions include 1) the discovery of 41 missing years in the oak chronology and 2) a shift of 54 yr for the oldest part back into the past. The oak chronology, was also extended with new samples as far back as 10,429 BP (8480 BC). In addition, the formerly tentatively dated pine chronology (Becker 1993) has been rebuilt and shifted to an earlier date. It is now positioned by 14C matching at 11,871-9900 BP (9922-7951 BC) with an uncertainty of +/20 yr (Kromer and Spurk 1998). With these new chronologies the 14C calibration curve can now be corrected, eliminating the discrepancy in the dating of the Younger Dryas/Preboreal transition between the proxy data of the GRIP and GISP ice cores (Johnsen et al. 1992; Taylor et al. 1993), the varve chronology of Lake Gościąż (Goslar et al. 1995) and the pine chronology (Becker, Kromer and Trimborn 1991).
    • 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.