Paleomagnetic detection of relative plate motions and an infrequently reversing core dynamo at 3.5 Ga

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Source: Science Magazine

Original: https://www.science.org/doi/abs/10.1126/science.adw9250?af=R...

Published: 2026-03-19T06:00:06Z

The paper presents the oldest evidence for differential plate tectonic movements at 3.48 Ga based on paleomagnetic data from the North Pole Dome in the East Pilbara Craton, Western Australia[1][7]. These movements reached about half a degree per million years and were in a direction similar to today's ocean floor spreading[1]. Evidence supports robust age constraints, including baked contact inversion tests on veins older than 3.44 Ga, a fold-through-strain test older than 3.3 Ga, and a stratabound reversal at 3.46 Ga, which is the oldest documented[1]. The study detects relative movements between two crustal blocks, a hallmark of plate tectonics[1]. The findings show the presence of an axially dipole nuclear dynamo with occasional reversals at 3.5 Ga[5][7]. The movements were fast, tens of centimeters per year, and lasted for tens of millions of years[1][3]. These processes indicate modern geophysical mechanisms on Earth 3.5 billion years ago[5].