Eoarchean
First era of the Archean Eon / From Wikipedia, the free encyclopedia
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The Eoarchean (IPA: /ˌiːoʊ.ɑːrˈkiːən/ EE-oh-ar-KEE-ən; also spelled Eoarchaean) 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. The beginnings of life on Earth have been dated to this era and evidence of archaea and cyanobacteria date to 3500 Mya, comparatively shortly after the Eoarchean. At that time, the atmosphere was without oxygen and the pressure values ranged from 10 to 100 bar (around 10 to 100 times the atmospheric pressure today).[2][3][4]
Quick Facts Chronology, Etymology ...
Eoarchean | ||||||
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4031 ± 3 – 3600 Ma | ||||||
Chronology | ||||||
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Etymology | ||||||
Name formality | Formal | |||||
Alternate spelling(s) | Eoarchaean | |||||
Usage information | ||||||
Celestial body | Earth | |||||
Regional usage | Global (ICS) | |||||
Time scale(s) used | ICS Time Scale | |||||
Definition | ||||||
Chronological unit | Era | |||||
Stratigraphic unit | Erathem | |||||
Time span formality | Formal | |||||
Lower boundary definition | Ten oldest U-Pb zircon ages | |||||
Lower boundary GSSA | Along the Acasta River, Northwest Territories, Canada 65.1738°N 115.5538°W / 65.1738; -115.5538 | |||||
Lower GSSA ratified | 2023[1] | |||||
Upper boundary definition | Defined Chronometrically | |||||
Upper GSSA ratified | 1991[citation needed] |
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