HR: 1330h
AN: PP32B-0298    [PDF]
TI: Changes in Atmospheric 14C Between 55 and 42 ky BP Recorded in a Stalagmite From Socotra Island, Indian Ocean
AU: * Weyhenmeyer, C E
EM: weyhen@llnl.gov
AF: Lawrence Livermore National Laboratory, Center for Accelerator Mass Spectrometry, L-397, Livermore, CA 94550 United States
AU: Burns, S J
AF: Department of Geosciences, University of Massachusetts, Morrill Science Center, Amherst, MA 01002 United States
AU: Fleitmann, D
AF: Institute of Geological Sciences, University of Berne, Baltzerstrasse 1, Bern, CH-3012 Switzerland
AU: Kramers, J D
AF: Institute of Geological Sciences, University of Berne, Baltzerstrasse 1, Bern, CH-3012 Switzerland
AU: Matter, A
AF: Institute of Geological Sciences, University of Berne, Baltzerstrasse 1, Bern, CH-3012 Switzerland
AU: Waber, H N
AF: Institute of Geological Sciences, University of Berne, Baltzerstrasse 1, Bern, CH-3012 Switzerland
AU: Reimer, P J
AF: Lawrence Livermore National Laboratory, Center for Accelerator Mass Spectrometry, L-397, Livermore, CA 94550 United States
AB: A record of atmospheric radiocarbon (14C) variations for a part of the last glacial period was obtained from a 1.7 m long stalagmite, M1-2, from Socotra Island in the Indian Ocean. The stalagmite radiocarbon values were corrected for 14C-free carbon added by water-rock interaction (dead carbon fraction), by using del 13C values of the calcite as a constraint. An age-depth model was developed from 25 high-precision U/Th measurements. The base of the stalagmite dates to 54.7 ky BP and it stopped growing around 42.2 ky BP. The difference between U/Th and 14C ages shows a smooth, steady increase from about 5,000 years at the base of the stalagmite to about 8,000 years at its top. Correspondingly, Delta 14C values increase from 500 per mil to about 1300 per mil, which indicates that concentrations of atmospheric 14C steadily increased between 55 and 42 yr BP. The record from Socotra Island does not show the large and rapid D14C changes previously recorded in a stalagmite from the Bahamas (Beck et al, Science 2001). The D14C values estimated from M1-2 are significantly higher than those estimated from a marine 14C record (foraminifera) from Cariaco Basin for the same time period (Hughen et al. in prep). In the latter, D14C values decrease to near 0 at about 44 ky BP. The most likely reason for this discrepancy are the two different time scales used; the Cariaco Basin is matched to the GISP2 timescale, which is approximately 5000 years younger than indicated by the stalagmite U/Th chronology (Burns et al, Science 2003). When the Cariaco basin record is adjusted to the M1-2 timescale, the D14C values for both datasets are similar.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0315 Biosphere/atmosphere interactions
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
DE: 3309 Climatology (1620)
DE: 4806 Carbon cycling
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting