First archaeomagnetic field intensity data from Ethiopia, Africa (1615 ± 12 AD)

Abstract

First archaeointensity determinations have been obtained from Ethiopia. Seven bricks (34 specimens) from the Däbsan archaeological remains were subjected to archaeointensity determination by means of classical Thellier–Thellier experiment including tests for magnetic anisotropy and magnetic cooling rate dependency. The age of the Däbsan Palace is well controlled by historical information: between 1603, when land grants were conceded to the Jesuits and the Catholicism was established as the official religion in Ethiopia, and the age of the Palace foundation in 1626–27. Successful archaeointensity determinations were obtained in 27 specimens from five individual bricks revealing an average field value of 33.5 ± 1.1 lT, which is 11–26% lower than expected values from global geomagnetic models based on historical and archaeomagnetic data. Global models for 1615 AD predict a low in central-southern Africa related to past location of the present Southern Atlantic Anomaly (SAA). Our results suggest that the field intensity in central Africa may have been slightly lower than global model predictions. This would indicate that the low could be probably more extended towards central-eastern Africa (or more intense) than previously considered. Further data from this region are especially welcome to delineate the evolution of the SAA.