The direction of geomagnetic field in Belgium since roman times and the reliability of archaeomagnetic dating

Abstract

Local geomagnetic secular variation curves are needed for improving models of the palaeofield changes and to increase the accuracy of archeomagnetic dating. Archaeomagnetic results from 34 baked structures are given as a first trial to construct directional secular variation curves for Belgium for the period from Post-Roman until the 18th century A.D. Often regular and irregular directional deviations are noticed in the walls of kilns. Large deviations of the remanent magnetization direction found in a big, circular, medieval pottery kiln can be explained by a combination of wall movement and magnetic distortion effects as the main origin. Two quicklime kilns, with unclear relationship to other features of the archaeological sites, were archaeomagnetically dated applying the British and French secular variation master curves for inclination and declination as a reference. This example highlights some of the difficulties encountered when applying existing secular variation master curves for dating.