• Present Status of Radiocarbon Calibration and Comparison Records Based on Polynesian Corals and Iberian Margin Sediments

      Bard, Edouard; Ménot-Combes, Guillemette; Rostek, Frauke (Department of Geosciences, The University of Arizona, 2004-01-01)
      In this paper, we present updated information and results of the radiocarbon records based on Polynesian corals and on Iberian Margin planktonic foraminifera. The latter record was first published by Bard et al. (2004a,b), with the subsequent addition of some data by Shackleton et al. (2004). These data sets are compared with the IntCal98 record (Stuiver et al. 1998) and with data sets based on other archives, such as varves of Lake Suigetsu (Kitagawa and van der Plicht 1998, 2000), speleothems from the Bahamas (Beck et al. 2001), and Cariaco sediments (Hughen et al. 2004). Up to 26,000 cal BP, the Iberian Margin data agree within the errors of the other records. By contrast, in the interval between 33,000 and 41,000 cal BP, the Iberian Margin record runs between the Lake Suigetsu and Bahamian speleothem data sets, but it agrees with the few IntCal98 coral data and the Cariaco record.
    • Radiocarbon Calibration and Comparison to 50 kyr BP with Paired 14C and 230Th Dating of Corals from Vanuatu and Papua New Guinea

      Cutler, K. B.; Gray, S. C.; Burr, G. S.; Edwards, R. L.; Taylor, F. W.; Cabioch, G.; Beck, J. W.; Cheng, H.; Moore, J. (Department of Geosciences, The University of Arizona, 2004-01-01)
      We calibrated portions of the radiocarbon time scale with combined 230Th, 231Pa, 14C measurements of corals collected from Espiritu Santo, Vanuatu and the Huon Peninsula, Papua New Guinea. The new data map 14C variations ranging from the current limit of the tree-ring calibration (11,900 calendar years before present [cal BP], Kromer and Spurk 1998, now updated to 12,400 cal BP, see Kromer et al., this issue), to the 14C-dating limit of 50,000 cal BP, with detailed structure between 14 to 16 cal kyr BP and 19 to 24 cal kyr BP. Samples older than 25,000 cal BP were analyzed with high-precision 231Pa dating methods (Pickett et al. 1994; Edwards et al. 1997) as a rigorous second check on the accuracy of the 230Th ages. These are the first coral calibration data to receive this additional check, adding confidence to the age data forming the older portion of the calibration. Our results, in general, show that the offset between calibrated and 14C ages generally increases with age until about 28,000 cal BP, when the recorded 14C age is nearly 6800 yr too young. The gap between ages before this time is less; at 50,000 cal BP, the recorded 14C age is 4600 yr too young. Two major 14C-age plateaus result from a 13 ppm drop in Delta-14C between 14-15 cal kyr BP and a 700ppm ppm drop in Delta-14C between 22-25 cal kyr BP. In addition, a large atmospheric Delta-14C excursion to values over 1000 ppm occurs at 28 cal kyr BP. Between 20 and 10 cal kyr BP, a component of atmospheric Delta-14C anti-correlates with Greenland ice delta-18O, indicating that some portion of the variability in atmospheric Delta-14C is related to climate change, most likely through climate-related changes in the carbon cycle. Furthermore, the 28-kyr excursion occurs at about the time of significant climate shifts. Taken as a whole, our data indicate that in addition to a terrestrial magnetic field, factors related to climate change have affected the history of atmospheric 14C.
    • Radiocarbon Calibration in the Anglo-Saxon Period; AD 495-725

      McCormac, F. G.; Bayliss, A.; Baillie, M. G. L.; Brown, D. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Radiocarbon dating has been rarely used for chronological problems relating to the Anglo-Saxon period. The "flatness" of the calibration curve and the resultant wide range in calendrical dates provide little advantage over traditional archaeological dating in this period. Recent advances in Bayesian methodology have, however, created the possibility of refining and checking the established chronologies, based on typology of artifacts, against 14C dates. The calibration process, within such a confined age range, however, relies heavily on the structural accuracy of the calibration curve. We have therefore re-measured, at decadal intervals, a section of the Irish oak chronology for the period AD 495-725. These measurements have been included in IntCal04.
    • Radiocarbon Results from a 13-kyr BP Coral from the Huon Peninsula, Papua New Guinea

      Burr, G. S.; Galang, Chrystie; Taylor, F. W.; Gallup, Christina; Edwards, R. Lawrence; Cutler, Kirsten; Quirk, Bill (Department of Geosciences, The University of Arizona, 2004-01-01)
      This paper presents radiocarbon results from a single Goniastrea favulus coral from Papua New Guinea which lived continuously between 13.0 and 13.1 kyr BP. The specimen was collected from a drill core on the Huon Peninsula and has been independently dated with 230Th. A site-specific reservoir correction has been applied to the results, and coral growth bands were used to calibrate individual growth years. Alternating density bands, which are the result of seasonal growth variations, were subsampled to provide 2 integrated 6-month 14C measurements per year. This allows for 20 independent measurements to be averaged for each decadal value of the 14C calibration, making these results the highest resolution data set available for this brief time range. The fine structure of the data set exhibits 14C oscillations with frequencies on the order of 4 to 10 yr, similar to those observed in modern coral 14C records.
    • Reidar Nydal (1926-2004)

      Jungner, Högne; Olsson, Ingrid U.; Scott, E. Marian (Department of Geosciences, The University of Arizona, 2004-01-01)
    • Review of Tropospheric Bomb 14C Data for Carbon Cycle Modeling and Age Calibration Purposes

      Hua, Quan; Barbetti, Mike (Department of Geosciences, The University of Arizona, 2004-01-01)
      Comprehensive published radiocarbon data from selected atmospheric records, tree rings, and recent organic matter were analyzed and grouped into 4 different zones (three for the Northern Hemisphere and one for the whole Southern Hemisphere). These 14C data for the summer season of each hemisphere were employed to construct zonal, hemispheric, and global data sets for use in regional and global carbon model calculations including calibrating and comparing carbon cycle models. In addition, extended monthly atmospheric 14C data sets for 4 different zones were compiled for age calibration purposes. This is the first time these data sets were constructed to facilitate the dating of recent organic material using the bomb 14C curves. The distribution of bomb 14C reflects the major zones of atmospheric circulation.
    • SHCal04 Southern Hemisphere Calibration, 0-11.0 cal kyr BP

      McCormac, F. G.; Hogg, A. G.; Blackwell, P. G.; Buck, C. E.; Higham, T. F. G.; Reimer, P. J. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Recent measurements on dendrochronologically-dated wood from the Southern Hemisphere have shown that there are differences between the structural form of the radiocarbon calibration curves from each hemisphere. Thus, it is desirable, when possible, to use calibration data obtained from secure dendrochronologically-dated wood from the corresponding hemisphere. In this paper, we outline the recent work and point the reader to the internationally recommended data set that should be used for future calibration of Southern Hemisphere 14C dates.
    • The 12,460-year Hohenheim Oak and Pine Tree-Ring Chronology from Central Europe—A Unique Annual Record for Radiocarbon Calibration and Paleoenvironment Reconstructions

      Friedrich, Michael; Remmele, Sabine; Kromer, Bernd; Hofmann, Jutta; Spurk, Marco; Kauser, Klaus Felix; Orcel, Christian; Küppers, Manfred (Department of Geosciences, The University of Arizona, 2004-01-01)
      The combined oak and pine tree-ring chronologies of Hohenheim University are the backbone of the Holocene radiocarbon calibration for central Europe. Here, we present the revised Holocene oak chronology (HOC) and the Preboreal pine chronology (PPC) with respect to revisions, critical links, and extensions. Since 1998, the HOC has been strengthened by new trees starting at 10,429 BP (8480 BC). Oaks affected by cockchafer have been identified and discarded from the chronology. The formerly floating PPC has been cross-matched dendrochronologically to the absolutely dated oak chronology, which revealed a difference of only 8 yr to the published 14C wiggle-match position used for IntCal98. The 2 parts of the PPC, which were linked tentatively at 11,250 BP, have been revised and strengthened by new trees, which enabled us to link both parts of the PPC dendrochronologically. Including the 8-yr shift of the oak-pine link, the older part of the PPC (pre-11,250 BP) needs to be shifted 70 yr to older ages with respect to the published data (Spurk 1998). The southern German part of the PPC now covers 2103 yr from 11,993-9891 BP (10,044-7942 BC). In addition, the PPC was extended significantly by new pine chronologies from other regions. A pine chronology from Avenches and Zurich, Switzerland, and another from the Younger Dryas forest of Cottbus, eastern Germany, could be crossdated and dendrochronologically matched to the PPC. The absolutely dated tree-ring chronology now extends back to 12,410 cal BP (10,461 BC). Therefore, the tree-ring based 14C calibration now reaches back into the Central Younger Dryas. With respect to the Younger Dryas-Preboreal transition identified in the ring width of our pines at 11,590 BP, the absolute tree-ring chronology now covers the entire Holocene and 820 yr of the Younger Dryas.
    • The Tropospheric 14CO2 Level in Mid-Latitudes of the Northern Hemisphere (1959-2003)

      Levin, Ingeborg; Kromer, Bernd (Department of Geosciences, The University of Arizona, 2004-01-01)
      A comprehensive tropospheric 14CO2 data set of quasi-continuous observations covering the time span from 1959 to 2003 is presented. Samples were collected at 3 European mountain sites at height levels of 1205 m (Schauinsland), 1800 m (Vermunt), and 3450 m asl (Jungfraujoch), and analyzed in the Heidelberg Radiocarbon Laboratory. The data set from Jungfraujoch (1986-2003) is considered to represent the free tropospheric background level at mid-latitudes of the Northern Hemisphere, as it compares well with recent (yet unpublished) measurements made at the marine baseline station Mace Head (west coast of Ireland). The Vermunt and Schauinsland records are significantly influenced by regional European fossil fuel CO2 emissions. The respective Delta-14CO2 depletions, on an annual mean basis, are, however, only 5 ppm less than at Jungfraujoch. Vermunt and Schauinsland both represent the mean continental European troposphere.