Assessing the GAD hypothesis with paleomagnetic data from large Proterozoic dike swarms

- VGP scatter illustrates geomagnetic field geometry for 0-5 Ma volcanics.
- Method shows reversal asymmetry in quadrupole contribution.
- Method deteriorates for smaller areal coverage and dikes.
- The Matachewan displays reversal asymmetry in the nondipole components.
- Geocentric axial dipole geometry remains viable for the Proterozoic.

Previous compilations of paleomagnetic studies have suggested that the Proterozoic geomagnetic field may have had as large as 12% quadrupole and 29% octupole components, relative to the dipole intensity. These values would have significant implications for geodynamo secular cooling and outer core dynamics, and for paleogeographic reconstructions. Herein we test the validity of one method, using paleomagnetic remanence of three Proterozoic large igneous provinces (LIPs), as well as younger paleomagnetic datasets, to determine zonal geomagnetic field models. Our results show that individual LIPs are not laterally widespread enough to support claims of significant global non-dipole field components in Proterozoic time. The geocentric axial dipole hypothesis remains viable for Proterozoic paleogeographic and geodynamic models.