On low-latitude virtual geomagnetic poles in Icelandic basalt lava sequences

In two paleomagnetic studies from the Neogene lava sequences of Iceland published in 1977, of the order of 10% of the reliably determined remanence directions corresponded to virtual pole positions below 40 degrees latitude. This was a larger proportion than found in most other volcanic locations. To explain it, Harrison [Harrison, C.G.A., 1980. Secular variation and excursions of the Earth's magnetic field. J. Geophys. Res. 85, 3511-3522] suggested that some 10% of the observed virtual geomagnetic poles (VGP) from Iceland might be distributed at random over the globe. These ''random poles" can be envisaged as dating from periods when the geomagnetic field is weak and dominated by variable non-dipole terms. Much additional data on remanence directions and intensities has been collected since then, and the present study analyses results from over 3500 lava flows in Iceland. The relative frequency and strength of virtual dipoles in this collection vary with the pole latitude in a similar way as in the collection studied by Harrison. Normalizing of remanence intensity data by the use of anhysteretic remanence (ARM) may improve the resolution of this type of analysis. (C) 1999 Elsevier Science B.V. All rights reserved.