Aportaciones de la arqueología al estudio del campo magnético terrestre durante la segunda edad del hierro

Résumé

The spatial and temporal evolution of the Earth’s magnetic fi eld in the past is a crucial point to understand its generation in the external core. But it is also required to investigate the solar activity, the 14C production and the debated relation between the geomagnetic fi eld and the past climate of the Earth. The geomagnetic field reconstructions may be obtained from studies on heated archaeological structures whose age is well-known, such as ovens, ceramic fragments, bricks, etc. From this information Palaeosecular Variation Curves (PSVC) are defi ned, describing the evolution of the geomagnetic field elements (declination, inclination and intensity) during a time interval in a specific region. The current curve for Iberia spans the last 3000 years, and it is defi ned from a sparse database, which is not even distributed, either spatial or temporally. The less defined periods (with less data) are the times previous to the Roman Age and the period between VI – IX A.D. The Palaeomagnetism Group of the Complutense University of Madrid has developed the archaeomagnetism in Spain. We are now focused on trying to fill the present gaps of the curve. Two different sites in the north of Portugal have been investigated, Castelinho and Crestelos, from the Second Iron Age. The collaboration between archaeologist and archaeomagnetist is the key point to improve the archaeomagnetic dating technique and to defi ne the past evolution of the Earth’s magnetic fi eld.