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Reconciling astrochronological and 40Ar/39Ar ages for the Matuyama-Brunhes boundary and late Matuyama Chron

Reconciling astrochronological and 40Ar/39Ar ages for the Matuyama-Brunhes boundary and late Matuyama Chron
Reconciling astrochronological and 40Ar/39Ar ages for the Matuyama-Brunhes boundary and late Matuyama Chron
When five Matuyama-Brunhes (M-B) boundary records from the North Atlantic are placed on isotope age models, produced by correlation of the ?18O record directly or indirectly to an ice volume model, the M-B boundary lies consistently at the young end of marine isotope stage 19 with a mean age for the midpoint of the reversal of 773.1 ka (standard deviation = 0.4 kyr), ?7 kyr younger than the presently accepted astrochronological age for this polarity reversal (780–781 ka). Two recently proposed revisions of the age of the 40Ar/39Ar Fish Canyon sanidine (FCs) standard to 28.201 ± 0.046 Ma and 28.305 ± 0.036 Ma would adjust 40Ar/39Ar ages applicable to the M-B boundary (and other reversals and excursions back to 1.2 Ma) to ages older than the new astrochronological ages by 8–24 kyr. The variables used to construct the ice volume models cannot account for the discrepancy. The FCs standard age that best fits the astrochronological ages is 27.93 Ma, which is within the uncertainty associated with the commonly used value of 28.02 (±0.16) Ma but younger than the recently proposed FCs ages. The EDC2 and EDC3 age models in the Dome C (Antarctic) ice core yield ages of 771.7 ka and 766.4 ka, respectively, for the 10Be flux peak that denotes the paleointensity minimum at the reversal boundary, implying that the EDC2 (rather than EDC3) age model is consistent with the observations from marine sediments, at least close to the M-B boundary.
argon ages, magnetic reversals, astrochronology, magnetic excursions, matuyama-brunhes boundary
1525-2027
Channell, J.E.T.
f37676da-640c-4bdc-8f9f-e2ffa43fe449
Hodell, D.A.
9f55a984-300c-40b9-8f10-ed47d62b46c6
Singer, B.S.
b1b1be19-1fd0-48b4-972e-97ef5b45b2c1
Xuan, C.
3f3cad12-b17b-46ae-957a-b362def5b837
Channell, J.E.T.
f37676da-640c-4bdc-8f9f-e2ffa43fe449
Hodell, D.A.
9f55a984-300c-40b9-8f10-ed47d62b46c6
Singer, B.S.
b1b1be19-1fd0-48b4-972e-97ef5b45b2c1
Xuan, C.
3f3cad12-b17b-46ae-957a-b362def5b837

Channell, J.E.T., Hodell, D.A., Singer, B.S. and Xuan, C. (2010) Reconciling astrochronological and 40Ar/39Ar ages for the Matuyama-Brunhes boundary and late Matuyama Chron. Geochemistry, Geophysics, Geosystems, 11 (12). (doi:10.1029/2010GC003203).

Record type: Article

Abstract

When five Matuyama-Brunhes (M-B) boundary records from the North Atlantic are placed on isotope age models, produced by correlation of the ?18O record directly or indirectly to an ice volume model, the M-B boundary lies consistently at the young end of marine isotope stage 19 with a mean age for the midpoint of the reversal of 773.1 ka (standard deviation = 0.4 kyr), ?7 kyr younger than the presently accepted astrochronological age for this polarity reversal (780–781 ka). Two recently proposed revisions of the age of the 40Ar/39Ar Fish Canyon sanidine (FCs) standard to 28.201 ± 0.046 Ma and 28.305 ± 0.036 Ma would adjust 40Ar/39Ar ages applicable to the M-B boundary (and other reversals and excursions back to 1.2 Ma) to ages older than the new astrochronological ages by 8–24 kyr. The variables used to construct the ice volume models cannot account for the discrepancy. The FCs standard age that best fits the astrochronological ages is 27.93 Ma, which is within the uncertainty associated with the commonly used value of 28.02 (±0.16) Ma but younger than the recently proposed FCs ages. The EDC2 and EDC3 age models in the Dome C (Antarctic) ice core yield ages of 771.7 ka and 766.4 ka, respectively, for the 10Be flux peak that denotes the paleointensity minimum at the reversal boundary, implying that the EDC2 (rather than EDC3) age model is consistent with the observations from marine sediments, at least close to the M-B boundary.

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More information

Published date: December 2010
Keywords: argon ages, magnetic reversals, astrochronology, magnetic excursions, matuyama-brunhes boundary
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 351180
URI: http://eprints.soton.ac.uk/id/eprint/351180
ISSN: 1525-2027
PURE UUID: f7aa6f7c-d6cc-4ca1-b318-5d4bf77efa77
ORCID for C. Xuan: ORCID iD orcid.org/0000-0003-4043-3073

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Date deposited: 16 Apr 2013 08:44
Last modified: 17 Dec 2019 01:36

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Contributors

Author: J.E.T. Channell
Author: D.A. Hodell
Author: B.S. Singer
Author: C. Xuan ORCID iD

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