New palaeointensity data from Holocene Icelandic lavas

We present rock magnetic and palaeointensity data from Holocene Icelandic lava flows, including historical and pre-historical lavas. Susceptibility versus temperature measurements indicate that the magnetic mineralogy is dominated by primary titanomagnetite that have experienced variable degrees of high-temperature oxidisation. The analyses also demonstrate that virtually all studied samples are thermally stable up to their Curie temperatures. Thellier palaeointensity experiments were carried out on 89 samples from fourteen different lava flows (spanning the age of 167 to 9450 cal. years BP). Microwave Thellier experiments were used for one third of the samples, while conventional thermal Thellier was used for the remainder; the two methods produced similar palaeointensities. Altogether, reliable absolute palaeointensity estimates were obtained from all of the lava flows, with values ranging from 38.2 ± 5.0 μT to 117.9 ± 8.3 μT. The new results indicate that the Holocene geomagnetic field intensity was more dynamic than suggested by the current field models, possibly including brief intervals of anomalously high field strength.