Polarity reversals and excursions are the most significant geomagnetic field changes generated in the liquid outer core of the Earth, therefore studying them helps understand geodynamo processes. This study examines the Matuyama-Brunhes (MB) reversal using a new reconstruction of the global geomagnetic field based on paleomagnetic data, termed GGFMB (Global Geomagnetic Field Model for the MB reversal). GGFMB covers 900-700 ka, including late Matuyama and early Brunhes. This allows us to also investigate the Kamikatsura excursion (ca. 888 ka). The model is based on 38 high-quality paleomagnetic sediment records with age control mostly independent of the magnetic signal. GGFMB suggests that the MB reversal began about ∼799 ka, when non-dipole field components increased and the axial dipole component decreased. The transitional fields first appeared on Earth’s surface in the high-latitude southern hemisphere and equatorial regions. The minimum dipole strength was reached around 780 ka and the axial dipole changed sign. After ∼10 kyr, the field stabilized in the normal polarity of the early Brunhes. The MB reversal lasted ∼29 kyr (from 799 to 770 ka) and had slower rate of dipole decay than recovery as well as lower dipole moment for several millennia before than after the reversal. According to GGFMB, the dipole moment during the Kamikatsura excursion was approximately half that of the current field and it was a regional excursion observed only over eastern Asia and North America. Our sediment data collection is heavily biased towards the northern hemisphere, thus more southern hemisphere records are needed to demonstrate GGFMB’s robustness in this region.

Key Points

A global geomagnetic field model for 900--700 ka is presented, including theMatuyama-Brunhes (MB) reversal and Kamikatsura excursion.

The mid-point of the MB reversal is at 780 ka, with an overall duration ofnearly 30 kyr.

The dipole field decays from moderate dipole moment in the late Matuyama and recovers quickly to higher values in the early Brunhes.

Plain Language Summary

The Earth’s magnetic field originates deep inside the planet and extends far into space, and it has undergone significant direction and intensity changes throughout geological history. The most extreme magnetic field changes are reversals, when the field changes its polarity and global field intensity reaches a minimum. We reconstruct the global geomagnetic field evolution over the time interval 900 000 to 700 000 years ago. The information about the magnetic field variations comes from the paleomagnetic signal recovered from sediment drill cores from locations all over the globe, and with good constraints on the ages of the material. Our model includes the Matuyama-Brunhes (MB) field reversal, which occurred ∼780 000 years ago. It provides a global view of this drastic field change, indicating, for example, that the recovery of the global field intensity was much faster than its decay and the average global field strength was lower for several millennia before than after the polarity change. Our model suggests that the reversal started at ∼799 ka, the actual polarity change of the axial dipole field occurred at ∼780 ka, and a stable normal polarity was reached at ∼770 ka. The whole process of the reversal therefore took ∼29 000 years.