科研之友
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摘要
Time-consuming and expensive radiometric dating techniques limit the number of dates available to construct absolute chronologies for high-resolution paleoclimate reconstructions. A recently developed rapid-screen C-14 dating technique reduces sample preparation time and per sample costs by 90%, but its accuracy has not yet been tested on shallow-water corals. In this study, we test the rapid-screen C-14 dating technique on shallow-water corals by comparing 44 rapid-screen C-14 dates to both high-precision C-14 dates and U/Th dates from mid- to late-Holocene fossil corals collected from the central tropical Pacific (2-4 degrees N, 157-160 degrees W). Our results show that 42 rapid-screen C-14 and U/Th dates agree within uncertainties, confirming closed-system behavior and ensuring chronological accuracy. However, two samples that grew approximate to 6500 years ago have calibrated C-14 ages approximate to 1000 years younger than the corresponding U/Th ages, consistent with diagenetic alteration as indicated by the presence of 15-23% calcite. Mass balance calculations confirm that the observed dating discrepancies are consistent with C-14 addition and U removal, both of which occur during diagenetic calcite recrystallization. Under the assumption that aragonite-to-calcite replacement is linear through time, we estimate the samples' true ages using the measured C-14 and U/Th dates and percent calcite values. Results illustrate that the rapid-screen C-14 dates of Holocene-aged fossil corals are accurate for samples with less than 2% calcite. Application of this rapid-screen C-14 method to the fossil coral rubble fields from Kiritimati Island reveal significant chronological clustering of fossil coral across the landscape, with older ages farther from the water's edge.
- 出版日期2016-3
- 单位西安交通大学
