First Global Paleomagnetic model including the Gauss-Matuyama reversal

Polarity reversals are among the most relevant events in Earth’s magnetic field evolution and are crucial to understand the dynamics within the outer core. During a reversal, the geomagnetic field deviates from an axial dipole, with non-dipolar components becoming dominant and resulting in a more complex spatial geometry. Therefore, paleomagnetic models based on Spherical Harmonic Analysis (SHA) have become an essential tool for analyzing the spatial and temporal features of the geomagnetic field during these events. However, to date, only the most recent magnetic field reversal, the Matuyama-Brunhes (MB) reversal (780 kyr BP), has been modeled.

Here we present and discuss our first SHA model of the second most recent reversal, the Gauss-Matuyama (GM), constructed from a recent compilation of high-quality paleomagnetic sediment records spanning from 2.4 to 2.7 Myr BP . Our model is based on 19 sediment cores, that have been carefully checked for independent age information, data quality and, where possible, regional consistency of the records. This provides a global distribution that allows us to analyze the spatial and temporal geometry of the GM worldwide. We further compare the field characteristics during the GM reversal to those of the MB reversal and to the present-day field. We discuss similarities and differences between the two geomagnetic field reversals.