Eoarchean
Geologic period
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The Eoarchean is the first era of the Archean Eon of the geologic record. It spans 431 million years, from the end of the Hadean Eon 4031 Mya to the start of the Paleoarchean Era 3600 Mya. Wikipedia
Occurred: 4,000 million years ago - 3,600 million years ago
Eon: Archean
Lower boundary definition: Ten oldest U-Pb zircon ages
Lower boundary GSSA: Along the Acasta River, Northwest Territories, Canada; 65°10′26″N 115°33′14″W / 65.1738°N 115.5538°W
Lower GSSA ratified: 2023
Upper boundary definition: Defined Chronometrically
Upper GSSA ratified: 1991