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^(238)U-^(234)U-^(230)Th-^(232)Th systematics and the precise measurement of time over the past 500,000 years

Edwards, R. Lawrence and Chen, J. H. and Wasserburg, G. J. (1987) ^(238)U-^(234)U-^(230)Th-^(232)Th systematics and the precise measurement of time over the past 500,000 years. Earth and Planetary Science Letters, 81 (2-3). pp. 175-192. ISSN 0012-821X.

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We have developed techniques to measure the ^(230)Th abundance in corals by isotope dilution mass spectrometry. This, coupled with our previous development of mass spectrometric techniques for ^(234)U and ^(232)Th measurement, has allowed us to reduce significantly the analytical errors in ^(238)U-^(234)-^(230)Th dating and greatly reduce the sample size. We show that 6 × 10^8 atoms of ^(230)Th can be measured to ±30‰ (2σ) and 2 × 10^(10) atoms of ^(230)Th to ± 2‰. 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 (2σ) 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 ^(232)Th 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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Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 1987 Elsevier Science. Received August 11, 1986; revised version received October 22, 1986. We are particularly grateful to a number of our colleagues who have spent many years working on various aspects of coral terraces and coral dating and were willing to share their expertise. We enjoyed the sound advice and enthusiastic support of T.L. Ku and A.L. Bloom. F.W. Taylor and R.K. Matthews provided well-documented and characterized samples. We have benefited from discussions with Fairchild Broecker and P. Aharon. The reviewers, H.F. Shaw and W.S. Broecker, and the editor, K.K. Turekian are thanked for constructive criticisms of the manuscript. Philosophical and technical advice from D.A. Papanastassiou is gratefully acknowledged. Funding for this work was specifically denied by the National Science Foundation. This work was possible through the support of the John D. MacArthur Fund using equipment supported by NASA grant No. NAG 9-43. Division Contribution No. 4371 (557).
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John D. MacArthur FundUNSPECIFIED
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Caltech Division of Geological and Planetary Sciences4371
Lunatic Asylum Lab557
Issue or Number:2-3
Record Number:CaltechAUTHORS:20131023-120433463
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Official Citation:R. Lawrence Edwards, J.H. Chen, G.J. Wasserburg, 238U234U230Th232Th systematics and the precise measurement of time over the past 500,000 years, Earth and Planetary Science Letters, Volume 81, Issues 2–3, January 1987, Pages 175-192, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42026
Deposited By: Ruth Sustaita
Deposited On:23 Oct 2013 20:36
Last Modified:09 Mar 2020 13:19

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