Abstract The variation of the Earth's magnetic field over the last millennia is poorly known in Africa, especially in Sub-Saharan Africa that represents less than 1% of the global archeomagnetic dataset. Fourteen iron furnaces from Kenya and Chad have been studied here for archeomagnetic purposes. These structures were dated by 14C from the 14th century in Kenya and from the 18-19th centuries in Chad. Samples, oriented with the plaster cap technique, have been subjected to thermal and alternating field demagnetization, rock magnetic analysis and paleointensity experiment, with the classical Thellier-Thellier technique corrected for anisotropy and cooling rate effects. New directional data (4 from Kenya and 10 from Chad) and one new paleointensity estimate from Kenya (43.5 ± 1.8 μT) were obtained. The Kenyan declinations are in good agreement with the geomagnetic global models, but the inclinations are lower and the intensity higher than predicted. For Chad, the new results prove the efficiency of the archeomagnetic dating, with a precision that is better than radiocarbon for the 18–19th centuries.

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来自肯尼亚和乍得的第一批考古磁数据：肯尼亚山和盖拉地块的铁炉分析

摘要 过去几千年来地球磁场的变化在非洲鲜为人知，尤其是在占全球考古磁数据集不到 1% 的撒哈拉以南非洲地区。来自肯尼亚和乍得的 14 座铁炉已在这里进行了研究，用于考古磁学目的。这些结构的年代可追溯到 14 世纪的肯尼亚和 18 至 19 世纪的乍得。使用石膏帽技术定向的样品已经进行了热和交变场退磁、岩石磁分析和古强度实验，经典的 Thellier-Thellier 技术针对各向异性和冷却速率效应进行了校正。获得了新的定向数据（来自肯尼亚的 4 个和来自乍得的 10 个）和来自肯尼亚的一项新的古强度估计（43.5 ± 1.8 μT）。肯尼亚的磁偏角与地磁全球模型非常吻合，但倾角低于预测，强度高于预测。对于乍得而言，新结果证明了古地磁测年的效率，其精度优于 18-19 世纪的放射性碳。