Holocene archeointensities from mid European ceramics, slags, burned sediments and cherts

The Earth’s geomagnetic field intensity in the past can be determined from archeological artifacts. These archeointensity data are important inputs for geomagnetic field models and local reference curves of Earth’s magnetic field. Although archeointensities have been measured on materials for more than half a century ago, data are still scarce before 1000 BC and for the Alpine area in general. This investigation presents new absolute archeointensity data from a time period of 5000–700 BC from Italy and Switzerland. The archeological materials that were studied are ceramics, copper slag, and burned sediments from fireplaces. In addition, we investigated archeointensities from burned cherts, in order to uncover if they are a suitable material for paleomagnetism. Rock magnetic properties of all samples indicate magnetite, and small amounts of maghemite and hematite in the pseudosingle domain range as the ferromagnetic carriers. The IZZI protocol was used for 96 specimens to obtain absolute intensities; 23 ceramics, slags and burned cherts passed the threshold criteria, which we applied. The choice of the threshold values allowed us to obtain the linear part in the Arai diagram, which corresponds to the characteristic remanent magnetization. Burned sediments did not pass the threshold criteria, most probably because they acquired a thermochemical remanent magnetization during their formation. We demonstrate that magnetic susceptibility and saturation isothermal remanent magnetization can be used to select cherts that are suitable for paleointensity determinations. After applying anisotropy and cooling rate corrections, the new archeointensity values are lower for some samples, but fit well with available models and other archeomagnetic data.