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175-10 Ediacaran Ultra-Weak Magnetic Field and the Avalon Explosion

Session: The Neoproterozoic Earth and Life Co-evolution, Part I

Presenting Author:

John Tarduno

Authors:

Tarduno, John A. ¹, Schneider, Jack², Huang, Wentao³, Ibanez-Mejia, Mauricio⁴, Cottrell, Rory D.⁵

(1) Department of Earth & Environmental Sciences, University of Rochester, University of Rochester, New York, USA; Department of Physics & Astronomy, University of Rochester, Rochester, New York, USA, (2) Department of Earth & Environmental Sciences, University of Rochester, Rochester, NY, USA, (3) State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources, Chinese Academy of Sciences, Beijing, China, (4) University of Arizona, Geosciences, Tucson, AZ, USA, (5) Department of Earth & Environmental Sciences, University of Rochester, Rochester, NY, USA,

Abstract:

Earth’s magnetic field has typically been viewed as a shield, protecting life from harmful radiation from space that might otherwise thwart the development of life and evolution (Uffen, Nature, 1963; Sagan, Nature, 1965; Tarduno et al., Science, 2015). Recent data suggest that this relationship between the geomagnetic shield and evolution flipped 575 to 565 million years ago during the Avalon explosion (Shen et al., Science, 2008), when the first macroscopic mobile animals of the Ediacaran Period evolved (Tarduno, Phys. Today, 2025). At this time, Earth’s magnetic field was on the verge of collapse, more than 10 times weaker than the present-day. Concurrently, oxygenation of the atmosphere and oceans was increasing (Pogge von Strandmann et al., Nat. Commun., 2015). We have recently suggested that the weakened magnetic field allowed more atmospheric hydrogen to escape to space, leading to greater oxygenation of the atmosphere and ocean which in turn stimulated evolution (Huang et al., Commun. Earth & Environ., 2024; Tarduno et al., Natl. Sci. Rev., 2025). Key factors allowing H and related oxygenation are the exact strength of the magnetic field and the duration of the ultra-weak dynamo state. Here, we review and update the expanding paleointensity data set for this interval, including new data that suggest the field may have intermittently vanished in the Ediacaran and Cryogenian Periods. We also consider whether the renewal of the geodynamo and restoration of magnetic shielding in the latest Ediacaran/Cambrian (Zhou et al., Nat. Commun., 2022; ESPL, 2024), likely related to the onset of nucleation of Earth’s solid inner core, is reflected in the palaeontologic record.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10582

Ediacaran Ultra-Weak Magnetic Field and the Avalon Explosion

Description

Session Format: Oral

Presentation Date: 10/21/2025

Presentation Start Time: 10:40 AM

Presentation Room: HBGCC, 304A

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