HR: 0800h
AN: PP21C-1573    [Abstracts]
TI: Limits and applications of high precision coral ²³⁰Th dating techniques
AU: * Shen, C
EM: river@ntu.edu.tw
AF: Department of Geosceices, National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Li, K
EM: r92224212@ntu.edu.tw
AF: Department of Geosceices, National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Sieh, K
EM: sieh@adelphia.net
AF: Seismological Laboratory, Caltech, 303 N. Mudd, MC 100-23, Pasadena, CA 91125 United States
AU: Natawidjaja, D
EM: danny@gps.caltech.edu
AF: Seismological Laboratory, Caltech, 303 N. Mudd, MC 100-23, Pasadena, CA 91125 United States
AU: Wang, X
EM: wang0452@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AU: Cheng, H
EM: cheng021@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AU: Edwards, R
EM: edwar001@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AB: Faithful interpretation of coral-inferred environmental and climatic records relies on accurate dating. Our newly-developed ²³⁰Th dating technique offers a precision better than 1 year. To approach this objective, chemistry has been refined and only brings about an equivalent age uncertainty of 1-2 months. The most important factor limiting the precision and accuracy is the initial ²³⁰Th content, incorporated into the growing matrix during crystallization. The initial ²³⁰Th can be constrained by building a ²³⁰Th/²³²Th vs. ²³⁴U/²³²Th isochron plot. The initial ²³⁰Th/²³²Th ratio for modern Porites corals, collected from Nanwan, southern Taiwan, is 5.2 (± 1.1) x 10^-6 (atomic ratio, hereafter), consistent with a value of 4.0 (± 0.5) x 10^-6 in the dissolved fraction of seawater and higher than that of 3.0 (± 0.7) x 10^-6 in the suspended particulate matter. The results indicate that the initial ²³⁰Th content is attributable mainly to the dissolved phase of seawater. Isochron plots for modern and fossil corals, sampled from Nanwan and Sumatran Islands, display little temporal and spatial variations of initial ²³⁰Th/²³²Th ratio. Applications of the technique given in this study include determining the occurrence of earthquakes in the Sumatran Islands and the variability of ENSO system in the equatorial Western Pacific Ocean.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4870 Stable isotopes (0454, 1041)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005