A first regional model of the past Earth’s magnetic field from Africa for the last 4,000 years

Holocene geomagnetic data from large areas such as the oceans, the African and South American continents, constitute only the 4–6% of the global datasets, limiting our understanding of the geomagnetic field features and evolution. So far, 48 studies from Africa sensu latu are available, the 14.5% of studies from Southern Africa, the 23% from Central Africa and 62.5% from the Norther Africa. About half of them are from archaeomagnetic data, and the rest are from volcanic and sedimentary records. Here, after selecting the available volcanic and archaeomagnetic data following a set of 3 FAIR (findability, accessibility, interoperability and reproducibility) principle-based criteria, we build a first regional geomagnetic model for Africa covering the last 4000 years, based on the revised version of the spherical cap harmonic analysis in 2 dimensions. The new regional model helps understanding the most important feature of the modern geomagnetic field anomaly, the South Atlantic Anomaly. The model shows, at the Earth’s surface, the westward migration of the SAA from the Indian Ocean over Africa since 1100 AD. Finally, we test the new model as a paleomagnetic dating tool by re-dating previous archaeomagnetic data from Africa, confirming that, despite being based on a still sparse database, it can be used to date other African archeological sites and the many active and dormant volcanoes of the East African System.