Bertrand Chanda J. H.

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Bertrand
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Chanda J. H.
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  • Article
    Cariaco Basin calibration update; revisions to calendar and 14C chronologies for core PL07-58PC
    (Dept. of Geosciences, University of Arizona, 2004) Hughen, Konrad A. ; Southon, John R. ; Bertrand, Chanda J. H. ; Frantz, Brian ; Zermeno, Paula
    This paper describes the methods used to develop the Cariaco Basin PL07-58PC marine radiocarbon calibration data set. Background measurements are provided for the period when Cariaco samples were run, as well as revisions leading to the most recent version of the floating varve chronology. The floating Cariaco chronology has been anchored to an updated and expanded Preboreal pine tree-ring data set, with better estimates of uncertainty in the wiggle-match. Pending any further changes to the dendrochronology, these results represent the final Cariaco 58PC calibration data set.
  • Preprint
    Marine-derived C-14 calibration and activity record for the past 50,000 years updated from the Cariaco Basin
    ( 2006-03-01) Hughen, Konrad A. ; Southon, John R. ; Lehman, Scott J. ; Bertrand, Chanda J. H. ; Turnbull, J.
    An expanded Cariaco Basin 14C chronology is tied to 230Th-dated Hulu Cave speleothem records in order to provide detailed marine-based 14C calibration for the past 50,000 years. The revised, high resolution Cariaco 14C calibration record agrees well with data from 230Th-dated fossil corals back to 33 ka, with continued agreement despite increased scatter back to 50 ka, suggesting that the record provides accurate calibration back to the limits of radiocarbon dating. The calibration data document highly elevated Δ14C during the Glacial period. Carbon cycle box model simulations show that the majority of observed Δ14C change can be explained by increased 14C production. However, from 45 to 15 ka, Δ14C remains anomalously high, indicating that the distribution of radiocarbon between surface and deep ocean reservoirs was different than it is today. Additional observations of the magnitude, spatial extent and timing of deep ocean Δ14C shifts are critical for a complete understanding of observed Glacial Δ14C variability.
  • Article
    Marine04 marine radiocarbon age calibration, 0-26 cal kyr BP
    (Dept. of Geosciences, University of Arizona, 2004) Hughen, Konrad A. ; Baillie, Mike G. L. ; Bard, Edouard ; Beck, J. Warren ; Bertrand, Chanda J. H. ; Blackwell, Paul G. ; Buck, Caitlin E. ; Burr, George S. ; Cutler, Kirsten B. ; Damon, Paul E. ; Edwards, R. Lawrence ; Fairbanks, Richard G. ; Friedrich, Michael ; Guilderson, Thomas P. ; Kromer, Bernd ; McCormac, Gerry ; Manning, Sturt ; Bronk Ramsey, Christopher ; Reimer, Paula J. ; Reimer, Ron W. ; Remmele, Sabine ; Southon, John R. ; Stuiver, Minze ; Talamo, Sahra ; Taylor, F. W. ; van der Plicht, Johannes ; Weyhenmeyer, Constanze E.
    New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally ratified to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0–26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision, and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically-dated tree-ring samples, converted with a box diffusion model to marine mixed-layer ages, cover the period from 0–10.5 cal kyr BP. Beyond 10.5 cal kyr BP, high-resolution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific 14C reservoir age information to provide a single global marine mixed-layer calibration from 10.5–26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring data sets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al. (this issue).
  • Article
    IntCal04 terrestrial radiocarbon age calibration, 0-26 cal kyr BP
    (Dept. of Geosciences, University of Arizona, 2004) Reimer, Paula J. ; Baillie, Mike G. L. ; Bard, Edouard ; Bayliss, Alex ; Beck, J. Warren ; Bertrand, Chanda J. H. ; Blackwell, Paul G. ; Buck, Caitlin E. ; Burr, George S. ; Cutler, Kirsten B. ; Damon, Paul E. ; Edwards, R. Lawrence ; Fairbanks, Richard G. ; Friedrich, Michael ; Guilderson, Thomas P. ; Hogg, Alan G. ; Hughen, Konrad A. ; Kromer, Bernd ; McCormac, Gerry ; Manning, Sturt ; Bronk Ramsey, Christopher ; Reimer, Ron W. ; Remmele, Sabine ; Southon, John R. ; Stuiver, Minze ; Talamo, Sahra ; Taylor, F. W. ; van der Plicht, Johannes ; Weyhenmeyer, Constanze E.
    A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0–24 cal kyr BP (Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from 0–26 cal kyr BP, but with much higher resolution beyond 11.4 cal kyr BP than IntCal98. Dendrochronologically-dated tree-ring samples cover the period from 0–12.4 cal kyr BP. Beyond the end of the tree rings, data from marine records (corals and foraminifera) are converted to the atmospheric equivalent with a site-specific marine reservoir correction to provide terrestrial calibration from 12.4–26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a coherent statistical approach based on a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The tree-ring data sets, sources of uncertainty, and regional offsets are discussed here. The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed in brief, but details are presented in Hughen et al. (this issue a). We do not make a recommendation for calibration beyond 26 cal kyr BP at this time; however, potential calibration data sets are compared in another paper (van der Plicht et al., this issue).