Magnetic anomalies in lava fields and consequences on the reliability of the palaeomagnetic signal recorded in lava flows: results from the Canary Islands

Abstract

In 1999, Jean-Pierre Valet and Vicente Soler published a study to explore the magnitude of deviations in direction and intensity of the ambient magnetic field induced by the crustal field and the possible consequences on paleomagnetic records. They measured, over more than two years, the total magnetic field above the surface of 12 lava flows in the islands of La Palma and Tenerife (Canary Islands, Spain) and observed that mean directions above the different flows showed values differing by 9° in declination and 6.5° in inclination. Also, virtual dipole moments differed by more than 10%. They concluded that paleomagnetic records could be significantly affected by this effect. Paleomagnetic measurements of a large number of samples or a spread-out sampling of lava flows would provide the best way to average out the contribution of anomalies.