No asymmetry in geomagnetic reversals recorded by 1.1-billion-year-old Keweenawan basalts

TitleNo asymmetry in geomagnetic reversals recorded by 1.1-billion-year-old Keweenawan basalts
Publication TypeJournal Article
Year of Publication2009
AuthorsSwanson-Hysell N.L, Maloof A.C, Weiss B.P, Evans D.AD
JournalNature Geoscience
Volume2
Pagination713 - 717
Date Published2009/09/13
Other Numbers15Maloof
Abstract

Interpreting the past latitude and geography of the continents from palaeomagnetic data relies on the key assumption that Earth’s geomagnetic field behaves as a geocentric axial dipole. The axial dipolar field model implies that all geomagnetic reversals should be symmetric. However, palaeomagnetic data from volcanic rocks produced by the 1.1-billion-year-old Keweenawan Rift system in North America have been interpreted to show asymmetric reversals, which had led to the suggestion that there was a significant non-axial dipole contribution to the magnetic field during this time1,2. Here we present high-resolution palaeomagnetic data that span three geomagnetic field reversals from a well-described series of basalt flows at Mamainse Point, Ontario, in the Keweenawan Rift. Our data show that each reversal is symmetric. We thus conclude that the previously documented reversal asymmetry is an artefact of the rapid motion of North America during this time. Comparisons of reversed and normal populations that were time-averaged over entire polarity intervals, or from sites not directly on either side of a geomagnetic reversal, have previously led to the appearance of reversal asymmetry.

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URLhttps://doi.org/10.1038/ngeo622
DOI10.1038/ngeo622
Short TitleNature Geoscience