Paleomagnetic evidence for the persistence or recurrence of the South Atlantic 
geomagnetic Anomaly

Shah, Jay; Koppers, Anthony A. P.; Leitner, Marko; Leonhardt, Roman; Muxworthy, Adrian R.; Heunemann, Christoph; Bachtadse, Valerian; Ashley, Jack A. D.; Matzka, J.

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Paleomagnetic evidence for the persistence or recurrence of the South Atlantic geomagnetic Anomaly

Authors

Shah, Jay
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Koppers, Anthony A. P.
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Leitner, Marko
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Leonhardt, Roman
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Muxworthy, Adrian R.
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Heunemann, Christoph
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Bachtadse, Valerian
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Ashley, Jack A. D.
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Matzka, J.
2.3 Earth's Magnetic Field, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

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http://meetingorganizer.copernicus.org/EGU2017/EGU2017-7555-3.pdf
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Citation

Shah, J., Koppers, A. A. P., Leitner, M., Leonhardt, R., Muxworthy, A. R., Heunemann, C., Bachtadse, V., Ashley, J. A. D., Matzka, J. (2017): Paleomagnetic evidence for the persistence or recurrence of the South Atlantic geomagnetic Anomaly, (Geophysical Research Abstracts Vol. 19, EGU2017-7555-3), General Assembly European Geosciences Union (Vienna 2017).

Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_2313891

Abstract

The South Atlantic geomagnetic Anomaly (SAA) is known as a region of the geomagnetic field that is approximately 25 T in intensity, compared to an expected value of 43 T. 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 T 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).