28. The half-life of 234-U

Bièvre, Paul De; Lauer, Karl; Duigou, Y. Le; Moret, H.; Muschenborn, G.; Spaepen, J.; Spernol, A.; Vaninbroukx, R.; Verdingh, V.

doi:10.1680/cndmaa.44555.0033

Cited by 21 publications

(6 citation statements)

References 19 publications

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“…Replicate analyses have been a All errors are 2OM; all isotope ratios are atomic ratios unless otherwise specified. b ),23s =1.551×10 --10 y 1 [61]; )~234=2.835×10 6 y I [59,60]; ),230=9.195×10 6 y 1 [58]. c ~234 U = {[234U/238U)//(234U//238U)eq ]_ 1} × 103 where (234U/238U)eq is the atomic ratio at secular equilibrium and is equal to )k238//h234 = 5.472× 10 5.…”

Section: Resultsmentioning

confidence: 99%

238U234U230Th232Th systematics and the precise measurement of time over the past 500,000 years

Edwards

Chen

Wasserburg

1987

Earth and Planetary Science Letters

1,101

100

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We have developed techniques to measure the 23°Th abundance in corals by isotope dilution mass spectrometry. This, coupled with our previous development of mass spectrometric techniques for 234U and 232Th measurement, has allowed us to reduce significantly the analytical errors in 23~U_ 234U-230Th dating and greatly reduce the sample size.We show that 6 × l0 s atoms of Z3°Th can be measured to ± 30%~ (2o) and 2 × 10 l° atoms of 23°Th to ± 2%e. The time over which useful age data on corals can be obtained ranges from a few years to -500 ky. The uncertainty in age, based on analytical errors, is ±5 y (20) for a 180 year old coral (3 g), ±44 y at 8294 years and +1.1 ky at 123.1 ky (250 mg of coral). We also report 232Th concentrations in corals (0.083-1.57 pmol/g) that are more than two orders of magnitude lower than previous values. Ages with high analytical precision were determined for several corals that grew during high sea level stands -120 ky ago. These ages lie specifically within or slightly postdate the Milankovitch insolation high at 128 ky and support the idea that the dominant cause of Pleistocene climate change is Milankovitch forcing.

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Section: Resultsmentioning

confidence: 99%

238U234U230Th232Th systematics and the precise measurement of time over the past 500,000 years

Edwards

Chen

Wasserburg

1987

Earth and Planetary Science Letters

1,101

100

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“…Importantly, these U-series observations were derived using older half-life values (De Bievre et al, 1971;Jaffey et al, 1971;Meadows et al, 1980), but the present study adopts the more recent half-life estimates of Cheng et al (2000). Recalculation to the newer half-lives shifts the d 234 U i systematically so that none of these samples have d 234 U i overlapping the modern marine value (Fig.…”

Section: Marine Isotope Stage 9 U-series Observations For Henderson Imentioning

confidence: 99%

The timing of sea-level high-stands during Marine Isotope Stages 7.5 and 9: Constraints from the uranium-series dating of fossil corals from Henderson Island

Andersen

Stirling

Potter

et al. 2010

Geochimica et Cosmochimica Acta

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Direct dating of fossil coral reefs using the U-series chronometer provides an important independent test of the Milankovitch orbital forcing theory of climate change. However, well-dated fossil corals pre-dating the last interglacial period (>130 thousand years ago; ka) are scarce due to, (1) a lack of sampling localities, (2) insufficient analytical precision in U-series dating methods, and (3) diagenesis which acts to violate the assumption of closed-system U-series isotopic decay in fossil corals. Here we present 50 new high-precision U-series age determinations for fossil corals from Henderson Island, an emergent coral atoll in the central South Pacific. U-series age determinations associated with the Marine Isotope Stage (MIS) 9 interglacial and MIS 7.5 interstadial periods are reported. The fossil corals show relatively little open-system U-series behaviour in comparison to other localities with fossil coral reefs formed prior to the last glacial cycle, however, open-system U-series behaviour is still evident in most of the dated corals. In particular, percent-level shifts in the [ 230 Th/ 238 U] act composition are observed, leading to conventional U-series ages that are significantly younger or older than the true sample age. This open-system U-series behaviour is not accounted for by any of the open-system U-series models, indicating that new models should be derived. The new U-series ages reported here support and extend earlier findings reported in Stirling et al. (2001), providing evidence of prolific coral reef development on Henderson Island at $320 ka, most likely correlated with MIS 9.3, and subsequent reef development at $307 ka during MIS 9.1, while relative sea-level was potentially $20 m lower than during MIS 9.3. The U-series ages for additional well-preserved fossil corals are suggestive of minor reef development on Henderson Island during MIS 7.5 (245-230 ka) at 240.3 ± 0.8 and 234.7 ± 1.3 ka. All U-series observations are consistent with the Milankovitch theory of climate change, in terms of the timing of onset and termination of the dated interglacial and interstadial periods. The best preserved samples also suggest that the oceanic 234 U/ 238 U during MIS 9 and MIS 7.5 was within five permil of the modern open ocean composition.

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“…The history of 234 U half-life measurements has recently been summarized by Cheng et al (2000). For many years a value of 244,500 ± 1000 kyr was used, based on the close agreement between two assessments: 244,600 ± 730 yrs (De Bievre et al 1971) and 244,400 ± 1200 yrs (Lounsbury and Durham 1971). The Commission on Radiochemistry and Nuclear Techniques assessed the half-lives of several nuclides and, for 234 U, reassessed the data of both of these studies together with five other studies and suggested a half-life of 245,500 ± 1,200 yrs (Holden 1989).…”

Section: Secular Equilibrium Materialsmentioning

confidence: 99%