Four-Dimensional paleomagnetic dataset: Late Neogene paleodirection and
paleointensity results from the Erebus Volcanic Province, Antarctica
Abstract
A fundamental assumption in paleomagnetism is that a geocentric axial
dipole (GAD) geomagnetic field structure extends to the ancient field.
Global paleodirectional compilations that span 0 - 10 Myr support a GAD
dominated field structure with minor non-GAD contributions, however, the
paleointensity data over the same period do not. In a GAD field, higher
latitudes should preserve higher intensity, but the current database
suggests that intensities are independent of latitude. To determine
whether the seemingly “low’ intensities from Antarctica reflect the
ancient field, rather than low quality data or inadequate temporal
sampling, we have conducted a new study of the paleomagnetic field in
Antarctica. This study focuses on the paleomagnetic field structure over
the Late Neogene. We combine and re-analyze new and published
paleodirectional and paleointensity results from the Erebus volcanic
province to recover directions from 107 sites that were both thermally
and AF demagnetized and then subjected to a set of strict selection
criteria and 28 paleointensity estimates from specimens that underwent
the IZZI modified Thellier-Thellier experiment and were also subjected
to a strict set of selection criteria. The paleopole
(205.6$^{\circ}$,
87.1$^{\circ}$) and
$\alpha_{95}$ (5.5$^\circ)$
recovered from our paleodirectional study supports the GAD hypothesis
and the scatter of the virtual geomagnetic poles is within the
uncertainty of that predicted by TK03 paleosecular variation model. Our
time averaged field strength estimate, 33.01 $\mu$T
$\pm$ 2.59 $\mu$T, is significantly
lower than that expected for a GAD field estimated from the present
field, but consistent with the long term average field.