Four-Dimensional Paleomagnetic Dataset: Plio-Pleistocene Paleodirection and Paleointensity Results From the Erebus Volcanic Province, Antarctica

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 0-5-million year 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 Plio-Pleistocene. We combine and reanalyze new and published paleodirectional and paleointensity results from the Erebus volcanic province to recover paleodirections from 98 sites that were both thermally and alternating field demagnetized and then subjected to a set of strict selection criteria and paleointensities from 26 sites from the Plio-Pleistocene that underwent the IZZI modified Thellier-Thellier experiment and were also subjected to a strict set of selection criteria. The paleopole (201.85 degrees, 87.65 degrees) and alpha(95) (5.51 degrees) recovered from our paleodirectional study supports the GAD hypothesis and the scatter of the virtual geomagnetic poles falls within the uncertainty of that predicted by TK03 paleosecular variation model. Our time-averaged field strength estimate, 33.57 +/- 2.71 mu T, is significantly weaker than that expected from a GAD field estimated by the present field. Plain Language Summary The geocentric axial dipole (GAD) hypothesis states that the Earth's magnetic field may be approximated by an Earth-centric dipole aligned with the rotation axis. This hypothesis is fundamental for paleogeographic reconstructions of the tectonic plates. While global paleomagnetic directions from the last 5 million years recover a predominately GAD field structure, paleointensity estimates over the same time period do not. In this study, we re-examine the paleomagnetic field structure in the Erebus Volcanic Province, Antarctica, and recover a robust data set of directional and intensity data. We then compare the paleopole and average dipole moment against a GAD field structure and model predictions of paleosecular variation.

Automated summary

The fundamental assumption in paleomagnetism is that the Earth's magnetic field can be approximated by a geocentric axial dipole (GAD). While global paleomagnetic directions from the last 5 million years support a GAD field structure, paleointensity estimates over the same period do not. This study reexamines the paleomagnetic field structure in Antarctica to determine the validity of low intensity readings.