Directional changes of the geomagnetic field in West Africa: Insights from the metallurgical site of Korsimoro

Abstract

This work shows the first archeomagnetic directions from Western Africa measured on 32 iron smelting kilns dated between 650 and 1800 AD. The archeological excavation of the vast metallurgical site of Korsimoro established the existence of four distinct iron-smelting techniques. The time-frame of each technique could be clearly determined with radiocarbon dating. Many of the kilns investigated in this study could also be dated individually with residual charcoals found in their inside. The results indicate that the inclination of the field changed gradually from shallow normal to shallow reversed during 800 to 1300 AD, and then went back to shallow normal around 1600–1700 AD. The declination was instead stable around 10°E between 800 and 1400 AD, thereafter it started changing towards North. This trend correlates well with available secular variation curves from the Balkan and from Spain, and indicates that the field variation in West Africa was similar to the one in Europe.