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| Titel |
Paleomagnetic evidence for the persistence or recurrence of the South Atlantic geomagnetic Anomaly |
| VerfasserIn |
Jay Shah, Anthony A. P. Koppers, Marko Leitner, Roman Leonhardt, Adrian R. Muxworthy, Christoph Heunemann, Valerian Bachtadse, Jack A. D. Ashley, Jürgen Matzka |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143801
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| Publikation (Nr.) |
 EGU/EGU2017-7555.pdf |
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| Zusammenfassung |
| The South Atlantic geomagnetic Anomaly (SAA) is known as a region of the geomagnetic
field that is approximately 25 μT in intensity, compared to an expected value of ∼43 μT.
Geomagnetic field models do not find evidence for the SAA being a persistent feature of the
geomagnetic field, however these models are constructed from paleomagnetic data that is
sparse in the southern hemisphere. We present a full-vector paleomagnetic study of 40Ar/39Ar
dated Late Pleistocene lavas from Tristan da Cunha in the South Atlantic Ocean (Shah et
al., 2016; EPSL). Paleointensity estimations using the Thellier method of eight
lava flows yield an average paleointensity of the Tristan da Cunha lavas as 18 ±
6 μT and an average virtual axial dipole moment (VADM) of 3.1 ± 1.2 × 1022
Am2. Comparing the VADM of the lava flows against the PADM2M, PINT and
SINT-800 databases indicates that the lava flows represent four distinct periods of
anomalously weak intensity in the South Atlantic between 43 and 90 ka ago, constrained
by newly obtained 40Ar/39Ar ages. This anomalously weak intensity in the Late
Pleistocene is similar to the present-day SAA and SAA-like anomalous behavior found in
the recent archeomagnetic study by Tarduno et al. (2015; Nat. Commun.). Our
dataset provides evidence for the persistence or recurrence of geomagnetic main field
anomalies in the South Atlantic, and potentially indicates such anomalies are the
geomagnetic field manifestation of the long-existing core-mantle boundary heterogeneity
seismically identified as the African Large Low Velocity Shear Province (LLSVP). |
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