A paleomagnetic and U-Pb geochronology study of the western end of the Grenville dyke swarm: Rapid changes in paleomagnetic field direction at ca. 585 Ma related to polarity reversals?

•∼585Ma Grenville dykes show changes in primary magnetization direction of ∼90° in <4My.•They appear to record a paleo-equatorial field during reversals of the main dipole field.•The changes may have occurred at a time when the Earth's field was frequently reversing.•This unstable field behaviour predated the first Ediacaran fauna by only a few million years.•Frequent reversals may help promote faunal evolution.