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

Abstract

AbstractA 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°, 87.65°) and α95 (5.51°) 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 μT, is significantly weaker than that expected from a GAD field estimated by the present field.