: Paleoclimatology: Eo-archean

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Eo-archean

The Eoarchean (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). The name comes from two Greek words: eos (dawn) and archaios (ancient). Rock formation was discovered in the Nuvvuagittuq Greenstone Belt in northern Québec, Canada, which has been dated to be 4,280 million years ago. These formations are presently under intense investigation. Carbonate precipitation acted as an important sink regulating the concentration of carbon dioxide in the atmosphere during this era. 3,850 million years old Greenland apatite shows evidence of Carbon-12 enrichment. This has sparked a debate whether there might have been photosynthetic life before 3.8 billion years. (Adapted from: https://en.wikipedia.org/wiki/Eoarchean)

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