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| Titel |
40Ar/39Ar age of a large amplitude directional fluctuation during the Matuyama-Brunhes reversal, Guadeloupe |
| VerfasserIn |
M. C. Brown, B. R. Jicha, B. S. Singer, J. Shaw |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068991
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| Zusammenfassung |
| We obtain new 40Ar/39Ar ages for three lavas that record part of the Matuyama-Brunhes
geomagnetic field reversal on the island of Basse-Terre, Guadeloupe. These lavas record a
reversed-transitional-reversed magnetostratigraphy and have a weighted mean isochron age
from 13 experiments of 784.6 ± 5.8 ka (2Ïă analytical uncertainty) relative to an age for the
Fish Canyon sanidine standard of 28.201 Ma. This is a far greater precision than obtained
through previous K-Ar dating. Our mean age is indistinguishable at the 2Ïă level
from the weighted mean isochron age of a large directional fluctuation preceding
the main directional change of the reversal recorded in six previously dated lavas
from Haleakala, Maui. In addition, the mean age of the Guadeloupe and Maui lavas
are distinct at the 2Ïă level from the ages of transitional lavas from Chile, Tahiti
and La Palma; previously determined to record a precursor phase of the reversal.
We suggest that lavas from Guadeloupe and Maui record a temporally coeval, but
morphologically non-uniform, large amplitude directional fluctuation between the
Matyuama-Brunhes precursor and the main directional change of the reversal. This
fluctuation in direction is consistent with observations from some North Atlantic, South
Atlantic and West Pacific marine sedimentary records of the Matuyama-Brunhes
reversal. Absolute palaeointensity estimates from the Guadeloupe lavas indicate
fluctuating field strength during this time. This intensity and directional variability
suggests there is a "mixed zone" connected to the total reversal process that lies
between the precursor and main directional reversal and this may be related to the
relative contributions of dipolar and non-dipolar fields seen at the Earth’s surface. |
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