Reconnaissance archaeomagnetic study of ancient bricks from Northern Poland

In total, 24 brick samples for archaeomagnetic studies were taken from ten historical buildings constructed between c.1280 AD and 1630 AD in northern Poland. Eight of them are from the gothic period. The Thellier-Thellier archaeointensity protocol was used in order to determine the ancient intensity and inclination registered by the bricks. In total, 28 representative specimens from 16 bricks gave successful archaeointensity determination with category B of results quality. For 25 of them the corrections for anisotropy of thermoremanent magnetization and cooling rate were introduced. A large number of specimens classified as category C (48%) is due to a high value of relative additivity check error d(AC) caused most probably by the presence of multi-domain magnetite. The curvature parameter k exceeds the limit value in 11 specimens. However, in the same sample specimens with k higher than 0.270 have provided very similar values of archaeointensity than those with k below this limit. Corrected data are convergent with the Central European master curve of archaeointensity. The corrections of raw data reduce their dispersion at specimen/sample level in most of sites.