Mesoarchean
| Mesoarchean | ||||||
|---|---|---|---|---|---|---|
 Banded iron formation created during the Mesoarchean era | ||||||
| Chronology | ||||||
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| Proposed redefinition(s) | 3490–2780 Ma Gradstein et al., 2012 | |||||
| Proposed subdivisions | Vaalbaran Period, 3490–3020 Ma Gradstein et al., 2012 | |||||
| Etymology | ||||||
| Name formality | Formal | |||||
| Alternate spelling(s) | Mesoarchaean | |||||
| Usage information | ||||||
| Celestial body | Era | |||||
| Stratigraphic unit | Erathem | |||||
| Time span formality | Formal | |||||
| Lower boundary definition | Defined Chronometrically | |||||
| Lower GSSA ratified | 1991[citation needed] | |||||
| Upper boundary definition | Defined Chronometrically | |||||
| Upper GSSA ratified | 1991[citation needed] | |||||
Karoo ice age* |
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The Mesoarchean (
Tectonics
The Mesoarchean era is thought to be the birthplace of modern-style plate subduction, based on geologic evidence from the Pilbara Craton in western Australia.[1][2] A convergent margin with a modern-style oceanic arc existed at the boundary between West and East Pilbara approximately 3.12 Ga. By 2.97 Ga, the West Pilbara Terrane converged with and accreted onto the East Pilbara Terrane.[2] A supercontinent, Vaalbara, may have existed in the Mesoarchean.[3]
Environmental conditions
Analysis of
The Mesoarchean atmosphere contained high levels of atmospheric
The Pongola glaciation occurred around 2.9 Ga, from which there is evidence of ice extending to a palaeolatitude (latitude based on the magnetic field recorded in the rock) of 48 degrees. This glaciation was likely not triggered by the evolution of photosynthetic cyanobacteria, which likely occurred in the interval between the Huronian glaciations and the Makganyene glaciation.[7]
Early microbial life
Microbial life with diverse metabolisms expanded during the Mesoarchean era and produced gases that influenced early Earth's atmospheric composition. Cyanobacteria produced oxygen gas, but oxygen did not begin to accumulate in the atmosphere until later in the Archean.[8] Small oases of relatively oxygenated water did exist in some nearshore shallow marine environments by this era, however.[9]
See also
- Geologic time scale – System that relates geologic strata to time
- Glacial period – Interval of time within an ice age that is marked by colder temperatures and glacier advances
- Ice age – Period of long-term reduction in temperature of Earth's surface and atmosphere
- Last glacial period– Period of major glaciations of the northern hemisphere (115,000–12,000 years ago)
References
External links
| Quaternary / Late Cenozoic |
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| Carboniferous–Permian |
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Late Ordovician glaciation |
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| Ediacaran |
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| Cryogenian-Snowball Earth | ||||||
| Paleoproterozoic |
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| Mesoarchean |
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| Related topics | ||||||
_Vaalbara_ancient_continent.png){kind=link}
