 |
| Titel |
An archeomagnetic record from southern Africa and its bearing on the history of the South Atlantic Anomaly |
| VerfasserIn |
John Tarduno, Rory Cottrell, Thomas Huffman, Michael Watkeys, Miriam Grigsby, Eric Blackman |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128379
|
| Publikation (Nr.) |
 EGU/EGU2016-8363.pdf |
|
|
|
|
|
| Zusammenfassung |
| The paucity of Southern Hemisphere archeomagnetic data limits the resolution of
paleosecular variation models, while at the same time important changes in the modern and
historical field, including the recent dipole decay, appear to originate in this region. We have
recently presented the first archeomagnetic data from Iron Age sites of southern
Africa (∼1000-1650 AD) (Tarduno et al., Nature Communications, 2015). Magnetic
data show a sharp intensity drop at ∼1300 AD, at a rate comparable to modern
field changes in the South Atlantic Anomaly (SAA), but to lower values. These
changes motivated our conceptual model whereby the recurrence of low field values
reflects magnetic flux expulsion from the core, promoted by the unusual core-mantle
boundary composition and structure beneath southern Africa as defined by seismology
(specifically the African Large Low Velocity Seismic Province, or LLVSP). Because the
African LLVSP is a longstanding structure, we expect this region to be a steady site
of flux expulsion, and perhaps the triggering site for reversals, on time scales of
millions of years. Here we discuss our ongoing efforts to extend the archeomagnetic
record from southern Africa back in time, and further develop the flux expulsion-
African LLVSP hypothesis, through new sampling and paleomagnetic analyses
of Iron Age burnt huts, grain bins and kraals from South Africa, Zimbabwe and
Botswana. Our preliminary analyses define a loop in the archeomagnetic curve for
southern Africa between ca. 400 and 1000 AD, absent in predictions from available
paleosecular variation models, that might record another flux expulsion episode. |
|
|
|
|
|
|