Secular Variations of Inclination of the Geomagnetic Field in SE Poland Between 1200 and 1800 AD

Abstract A set of brick samples from 26 historical buildings in SE Poland was taken for archeomagnetic study. As a result of this study, the secular variations of inclination of the geomagnetic field from 1200 to 1800 AD were defined for SE Poland. The course of them is approximately the same as obtained in other parts of Europe. The only remarkable difference is a more rapid and deeper drop of inclination noted in SE Poland at the end of the 18th century. The regional curve of secular variations of inclination for SE Poland differs substantially from the coeval curve defined earlier for N Poland (Gdańsk) in their segments dated at the first half of the 18th century, where a deep minimum of inclination was disclosed in the bricks from N Poland only. The reuse of medieval bricks for the construction of objects giving this minimum or later secondary heating of original bricks can be a reason for the difference observed. Further archeomagnetic studies of the bricks of the last millennium are necessary in SE Poland to eliminate the gaps and uncertainties in the regional curve of secular variations of inclination.