High-precision U-series measurements of more than 500,000 year old fossil corals |
| |
| Authors: | Morten B Andersen Claudine H Stirling Emma-Kate Potter Alex N Halliday Steven G Blake Malcolm T McCulloch Bridget F Ayling Michael O'Leary |
| |
| Institution: | 1. Laboratoire de Géochimie et Métallogénie, Département Géosciences Marines, IFREMER, Z.I. Pointe du diable, BP 70, 29280 Plouzané, France;2. CNRS UMR 6538 Laboratoire Domaines Océaniques, Institut Universitaire Européen de la Mer, Université de Brest, Place Nicolas Copernic, 29280 Plouzané, France;3. Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611, USA;4. U.S. Geological Survey, 973 Denver Federal Center, Denver, CO 80225, USA;5. Department of Earth and Environmental Sciences, University of Ottawa, Advanced Research Complex, 25 Templeton St., Ottawa, Ontario K1N 6N5, Canada;1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi''an 710075, China;2. Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China;3. Department of Chemistry and Laser Chemistry Institute, Fudan University, Shanghai 200433, China |
| |
| Abstract: | Robust, independent age constraints on the absolute timing of climate events based on the U-series dating of fossil coral are sparse before the last glacial cycle. Using multiple-collector inductively coupled plasma mass spectrometry with multiple-Faraday protocols, we are able to date ～ 600 ka samples with an uncertainty of better than ± 15 ka (2σ), representing a three-fold improvement in precision compared with previous techniques. Using these methods, we report U-series measurements for a suite of > 500 thousand year old (ka) corals from Henderson Island, an emergent atoll in the south-central Pacific Ocean. The fossil corals show extraordinarily little diagenetic alteration for their age and the best-preserved sample yields a U-series age of 600 ± 15 ka (2σ), which overlaps with the timing of the warm Marine Isotope Stage (MIS) 15 interglacial. The open-system model of Villemant and Feuillet Villemant B. and Feuillet N. (2003) Dating open systems by the 238U–234U–230Th method: application to Quaternary reef terraces. Earth and Planetary Science Letters 210(1–2), 105–118.] and the linear regression (or open-system isochron) is clearly limited for such old samples. However, the open-system model developed by Thompson et al. Thompson W.G., Spiegelman M.W., Goldstein S.L., and Speed R.C. (2003) An open-system model for U-series age determinations of fossil corals. Earth and Planetary Science Letters 210(1–2), 365–381.] appears to reliably correct for open-system effects in roughly half of the corals, giving a MIS 15 origin for these. Thus the data provide evidence that the systematic addition of 230Th and 234U through α-recoil is a dominant open-system process occurring in the Henderson Island fossil reef system. Several coral samples yield significantly older Thompson et al. open-system ages between 650 and 750 ka. The uncertainty on these ages (typically ± 30 kyrs) is too great for precise assignment but most data overlap with the MIS 17 interglacial. The reliability of these ages is currently unclear. It is shown that separate aliquots of the same coral can yield different Thompson model ages. Therefore, there appear to be additional diagenetic mechanisms that create further anomalous excursions in the U-series systematics, limiting the reliability of the Thompson et al. open-system model. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
