High-precision U-238-U-234-Th-230 disequilibrium dating of the recent past: a review

Although it was demonstrated 20 years ago that mass spectrometric U-Th methods are capable of high-precision dating of young corals, the use of this approach to decipher recent environmental, climatic and archaeological records is still restricted and its potential has not yet been widely recognised. U-Th methods are typically used to determine the ages of carbonate materials such as speleothem and coral. Dating young carbonates of this sort is challenging. Their extremely low Th-230 content necessitates stricter instrumental and laboratory conditions than those required for dating older samples. Moreover, analyses must be corrected for the presence of non-radiogenic Th-230, which is proportionally far more significant than in older samples. Nevertheless, 2 sigma precisions of around +/- 1-10 years are readily achievable for pristine coral samples dating from the last 500 years. Although the range of analytical precisions for speleothems may vary more widely depending on U concentrations and levels of non-radiogenic Th-230 correction, published studies reveal 2 sigma precisions of around +/- 10-80 years for typical speleothems. This paper demonstrates how the U-Th method may be applied to establish the causes of recent coral mortality, to determine the recurrence interval of extreme wave events, to investigate earthquake frequency and neotectonic uplift, to reconstruct recent climatic history, and to understand settlement patterns and sociopolitical changes in Polynesia prior to European contact. (C) 2009 Elsevier Ltd. All rights reserved.