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Timing of the Brunhes-Matuyama transition constrained by U-series disequilibrium.

ABSTRACT: U-series disequilibrium measurements carried out on thermogenic travertine samples from a 12.6 m-long core and a 10 m-thick section from southeastern Morocco yielded finite ages ranging from 500 ka to the present-day, as well as two clusters determined to be older than 500 ka. The calculation of initial ²³⁴U/²³⁸U activity ratios in all samples younger than 500 ka shows high, reasonably constant values, with an average of 5.172?±?0.520 (one standard deviation). Assuming that this value prevailed for periods older than 500 ka, we derived ages of up to approximately 1.2?Ma using the initial ²³⁴U excess decay. Our results indicate that the two older clusters have ages of 776?±?14 ka for samples from between 8 and 10.1?m and 1173?±?22 ka for deeper samples respectively. The palaeomagnetic record of the core shows normal polarity inclinations from the surface to around 9?m followed by reverse polarity inclination and antipodal declinations. The inversion is attributed to the Brunhes-Matuyama transition. ²³⁴U excess ages for the interval corresponding to the part of the core where the polarity inversion occurred are in the range of 735?±?51 to 794?±?54 ka, with an arithmetic mean value of 776?±?14 ka for the B-M transition. This age is in good agreement with that determined previously using other dating methods.

SUBMITTER: Ghaleb B

PROVIDER: S-EPMC6465598 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Timing of the Brunhes-Matuyama transition constrained by U-series disequilibrium.

Ghaleb Bassam B Falguères Christophe C Carlut Julie J Pozzi Jean-Pierre JP Mahieux Geoffroy G Boudad Larbi L Rousseau Louis L

Scientific reports 20190415 1

U-series disequilibrium measurements carried out on thermogenic travertine samples from a 12.6 m-long core and a 10 m-thick section from southeastern Morocco yielded finite ages ranging from 500 ka to the present-day, as well as two clusters determined to be older than 500 ka. The calculation of initial <sup>234</sup>U/<sup>238</sup>U activity ratios in all samples younger than 500 ka shows high, reasonably constant values, with an average of 5.172 ± 0.520 (one standard deviation). Assuming that ...[more]

PMID: 30988519

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Timing of the Brunhes-Matuyama transition constrained by U-series disequilibrium.

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Timing of the Brunhes-Matuyama transition constrained by U-series disequilibrium.

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