Some statistical properties of palaeomagnetic directions in Icelandic lava flows

Abstract

Summary. This paper extends the efforts of Kristjansson & McDougall to obtain a semi‐quantitative description of various long‐term (0.1–10 Myr) properties of the geomagnetic field in Iceland. Due to the long time intervals between eruptions of the lavas recording the field, local average and stochastic properties are emphasized, rather than detailed aspects such as pole paths. These properties can be represented by smooth functions of virtual‐pole latitude. It is possible to describe both the frequency distribution of virtual poles in latitude and the estimated frequency of geomagnetic reversals, by a simple process of random walk of the pole. This is also in agreement with the observed long‐term symmetry of the reversal process, and demonstrates that memory effects are unnecessary to account for the behaviour of the field. The average transition time for the field isofthe order of 5—6000yr. Right‐handedness is a pervasive property of the field in Iceland, apparently increasing with age. It is demonstrated that the size of palaeomagnetic collections in lava sequences has to be much larger than 20 units in order to yield consistent values of statistical parameters for mean palaeofield directions. Copyright © 1985, Wiley Blackwell. All rights reserved