 |
| Titel |
New insights into the radiocarbon calibration based on 14C and U-Th dating of corals drilled offshore Tahiti (IODP Expedition #310) |
| VerfasserIn |
Nicolas Durand, Pierre Deschamps, Edouard Bard, Bruno Hamelin, Gilbert Camoin, Alexander L. Thomas, Gideon M. Henderson, Yusuke Yokoyama |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037630
|
|
|
|
|
|
| Zusammenfassung |
| Beyond the high-precision tree-ring calibration, the fossil corals are the most reliable archive
that can be used to calibrate the radiocarbon time scale. In this contribution, we present a new
radiocarbon dataset based on paired 14C and U-Th dating of fossil shallow-water tropical
corals drilled offshore Tahiti during the IODP Expedition 310 “Tahiti Sea-Level”. Before 14C
and U-Th analyses, rigorous screening criteria have been applied in order to select pristine
aragonitic coral skeletons and avoid those displaying any post-mortem diagenesis that alters
original ages. In particular, we made a significant effort to improve detection and
quantification of very small amount of secondary calcite in the aragonitic coral lattice using
X-ray diffraction measurements [1]. In addition, we apply a strict screening criterion based
on δ234U. However, the new Tahiti dataset allow to refine the previous tolerance
ranges previously adopted. More than 60 radiocarbon dates were processed at the
Laboratoire de Mesure du Carbone 14 (Saclay, France) with the ARTEMIS AMS facility.
This new Tahiti record provides new data to the radiocarbon calibration for two
distinct time windows: for the interval between 29,200 and 36,200 years BP and
for the last deglaciation period, with especially, a higher resolution (40 data) for
the 14,000 - 16,000 years BP time interval. These new data extend the previous
Tahiti record beyond 13,900 years BP which was the oldest U-Th age obtained on
cores drilled onshore in the modern Tahiti barrier reef [2, 3]. These new results are
compared with 14C chronologies from other corals, those of Barbados [4, 5] and those
from other Pacific islands (Mururoa, Vanuatu, Marquesas, Christmas), and from the
Cariaco Basin sediment [6, 7], the Iberian Margin sediment [8, 9] and the Bahamian
speleothem [10] records. The new 14C dataset from the corals drilled offshore Tahiti
allows to validate the precision and accuracy of other records either directly dated
by U-Th or tuned to a dated target, with a special emphasise for the Heinrich 1
event for which there is a debate about interpretating the discrepancies observed
between the different records [7]. For this time period, 15,000 - 17,500 cal ky BP, the
Tahiti record supports the few data from the Iberian Margin record and from the
Bahamas speleothems, but is in clear conflict with the Cariaco Basin record. The Tahiti
record also allows to refine the significant variations of the atmospheric Î14C during
the Bølling warming period, that might be interpreted as changes in the global
carbon cycle due to variations in the rates of exchange between the different carbon
pools.
[1] Sepulcre S, Durand N, Bard E. 2009, Glob. Planet. Sci. 66, 1.
[2] Bard et al. 1996, Nature 382, 241.
[3] Bard E, Hamelin B, Delanghe-Sabatier D. 2010, Science DOI:10.1126/science.1180557.
[4] Fairbanks RG et al. 2005, Quaternary Science Reviews 24, 1781.
[5] Peltier WR & Fairbanks RG. 2006, Quaternary Science Reviews 25, 3322.
[6] Hughen et al. 2006, Quaternary Science Reviews 25, 3216.
[7] Reimer et al. 2009, Radiocarbon 51, 1111.
[8] Bard E, Rostek F, Ménot-Combes G. 2004, Science 303, 178.
[9] Bard E, Ménot-Combes G, Rostek F. 2004, Radiocarbon 46, 1189.
[10] Hoffmann et al. 2010, Earth and Planetary Science Letters 289, 1. |
|
|
|
|
|
|