Refining the high-fidelity archaeointensity curve for western Europe over the past millennium: analysis of Tuscan architectural bricks (Italy).

New archaeointensity results were obtained from 14 groups of baked-brick fragments collected in and around Pisa (Tuscany, Italy). The fragments were assembled from civil and religious buildings whose dating of construction or renovation, over the past millennium, was constrained by documentary sources. This collection, analysed using the Triaxe protocol, was found particularly suitable for intensity experiments, with a success rate of c. 84% corresponding to 276 fruitful specimens associated with 125 independent brick fragments. The Tuscan data clearly show a peak in intensity at the transition between the sixteenth and seventeenth centuries. They are also in very good agreement with, and complementary to, a dense dataset previously obtained in France. Considering the results available within a 700 km radius of Beaune (between Paris and Pisa), all satisfying a set of quality criteria, a mean geomagnetic field intensity variation curve was constructed for the past millennium using a newly developed transdimensional Bayesian technique. This curve, which thus incorporates the new Tuscan results, allows a better recognition of three intensity peaks (during the twelfth century, the fourteenth century and around AD 1600) in western Europe. The detail of this curve is a clear illustration of the centennial-scale resolution that can be achieved using accurate archaeointensity data.