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?

摘要: Abstract A paleomagnetic study of the western end ∼585 Ma Grenville dyke swarm shows that individual dykes are characterized by high coercivity and unblocking temperature magnetizations can differ in direction as much 90°. Field tests including baked contact studies continuity along strike, suggest primary. Precise U–Pb baddeleyite dating on these indicates changes magnetization ∼90° occur less than 4 million years, their close temporal association with reversals axial dipole field certain recording an equatorial a transitional between opposite polarity states. The documented instability Earth's occurs 10 Myr before first recorded appearance macroscopic multi-cellular organisms Earth, inviting speculation extended period frequent magnetic may play part faunal evolution.