| Palaeos: | |
The Archean Eon |
| Archean | The Neoarchean Era |
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| Timescale Chaotian Hadean Eoarchean Paleoarchean Mesoarchean Proterozoic Phanerozoic |
Introduction to the Archean |
The Neoarchean spans the period of time from 2,800 to 2,500 million years ago; the period being defined chronometrically and not referenced to a specific level in a rock section on Earth. Oxygenic photosynthesis first evolved in this era and was accountable for the oxygen catastrophe which was to happen later in the Paleoproterozoic from a poisonous buildup of oxygen in the atmosphere, produced by these oxygen producing photoautotrophs, which evolved earlier in the Neoarchean. The supercontinent Kenorland formed during this period, about 2.7 billion years ago. - Wikipedia
Pending revision of this page, the following material is lifted verbatim from Peripatus - Archaean Eon:
"Schopf & Walther (1983) reported rare trichomes from the ca. 2800 Ma Fortescue Group, Western Australia. The fossils resemble oscillatorian cyanobacteria, but they are not taxonomically diagnostic; similar morphologies occur among both sulfur-oxidizing and sulfate-reducing bacteria. More diverse microfossils have been reported from the ca 2500 Ma Transvaal Supergroup, South Africa. Silicified microstromatolites and associated intraclasts from platform environments contain 1-5 m m diameter coccoids and thin filamentous sheaths interpreted as primary producers as well as tiny rods interpreted as heterotrophic bacteria (Lanier 1986). Chert nodules in deeper basinal limestones contain carbonate-lined filamentous sheaths up to 27 m m in cross-sectional diameter (Klein et al. 1987)."
"Stromatolites become increasingly abundant in younger Archean successions, a pattern as likely to reflect craton growth as evolutionary change. By the end of the eon, extensive carbonate platforms supported widespread mat-building communities that almost certainly included cyanobacteria."
- (After Knoll 1996.)
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