An Archean Geomagnetic Reversal in the Kaap Valley Pluton, South Africa
- 16 August 1996
- journal article
- other
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 273 (5277) , 943-946
- https://doi.org/10.1126/science.273.5277.943
Abstract
The Kaap Valley pluton in South Africa is a tonalite intrusion associated with the Archean Barberton Greenstone Belt. Antipodal paleomagnetic directions determined from the central and marginal parts of the pluton record a geomagnetic reversal that occurred as the pluton cooled. The age of the reversal is constrained by an 40Ar/39Ar plateau age from hornblende at 3214 ± 4 million years, making it the oldest known reversal. The data presented here suggest that Earth has had a reversing, perhaps dipolar, magnetic field since at least 3.2 billion years ago.Keywords
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