Mesoarchean

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title: "Mesoarchean" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["archean", "geological-eras", "precambrian-geochronology"] description: "Third era of the Archean Eon" topic_path: "philosophy" source: "https://en.wikipedia.org/wiki/Mesoarchean" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Third era of the Archean Eon ::

::data[format=table title="Infobox geologic timespan"]

Field	Value
name	Mesoarchean
color	Mesoarchean
top_bar	all time
time_start
time_end
timeline	Mesoarchean
proposed_boundaries1	3490–2780 Ma
proposed_boundaries1_ref	Gradstein et al., 2012
proposed_subdivision1	Vaalbaran Period, 3490–3020 Ma
proposed_subdivision1_coined	Gradstein et al., 2012
proposed_subdivision2	Pongolan Period, 3020–2780 Ma
proposed_subdivision2_coined	Gradstein et al., 2012
name_formality	Formal
alternate_spellings	Mesoarchaean
celestial_body	earth
usage	Global (ICS)
timescales_used	ICS Time Scale
chrono_unit	Era
strat_unit	Erathem
timespan_formality	Formal
lower_boundary_def	Defined Chronometrically
lower_gssa_accept_date
upper_boundary_def	Defined Chronometrically
upper_gssa_accept_date
image_map	3000 Ma paleoglobe.png
::

| name = Mesoarchean | color = Mesoarchean | top_bar = all time | time_start = | time_end = | timeline = Mesoarchean | proposed_boundaries1 = 3490–2780 Ma | proposed_boundaries1_ref = Gradstein et al., 2012 | proposed_subdivision1 = Vaalbaran Period, 3490–3020 Ma | proposed_subdivision1_coined = Gradstein et al., 2012 | proposed_subdivision2 = Pongolan Period, 3020–2780 Ma | proposed_subdivision2_coined = Gradstein et al., 2012 | chrono_name = | strat_name = | name_formality = Formal | name_accept_date = | alternate_spellings = Mesoarchaean | former_names = | proposed_names = | celestial_body = earth | usage = Global (ICS) | timescales_used = ICS Time Scale | chrono_unit = Era | strat_unit = Erathem | proposed_by = | timespan_formality = Formal | lower_boundary_def = Defined Chronometrically | lower_gssa_accept_date = | upper_boundary_def = Defined Chronometrically | upper_gssa_accept_date = |image_map=3000 Ma paleoglobe.png|caption_map=A reconstruction of the Earth's continents during the middle Mesoarchean, c. 3 Ga.|image_art=Banded iron formation (Goldman Meadows Formation, Mesoarchean; Atlantic City Iron Mine, South Pass, Wyoming, USA) 2 (30749219994).jpg|caption_art=Banded iron formation created during the Mesoarchean era|image_outcrop=Archean.png|caption_outcrop=Artist impression of the Archean eon}}

The Mesoarchean ( , also spelled Mesoarchaean) is a geologic era in the Archean Eon, spanning , which contains the first evidence of modern-style plate subduction and expansion of microbial life. The era is defined chronometrically and is not referenced to a specific level in a rock section on Earth.

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. 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.

Environmental conditions

Analysis of oxygen isotopes in Mesoarchean cherts has been helpful in reconstructing Mesoarchean surface temperatures. These cherts led researchers to draw an estimate of an oceanic temperature around 55-85°C (131-185 Fahrenheit), while other studies of weathering rates postulate average temperatures below 50°C (122 Fahrenheit).

The Mesoarchean atmosphere contained high levels of atmospheric methane and carbon dioxide, which could be an explanation for the high temperatures during this era.

Pongola glaciation 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.

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. Small oases of relatively oxygenated water did exist in some nearshore shallow marine environments by this era, however.

References

References

1. (2010). "Mesoarchean subduction processes: 2.87 Ga eclogites from the Kola Peninsula, Russia". Geology.
2. (2007). "The Mesoarchean emergence of modern-style subduction". Gondwana Research.
3. (2009). "Validating the existence of Vaalbara in the Neoarchean". Precambrian Research.
4. (2006). "Weathering of quartz as an Archean climatic indicator". Earth and Planetary Science Letters.
5. (2003). "High Archean climatic temperature inferred from oxygen isotope geochemistry of cherts in the 3.5 Ga Swaziland Supergroup, South Africa". Geological Society of America Bulletin.
6. (2013). "Nitrogen isotopic composition and density of the Archean atmosphere". Science.
7. (2005). "The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis". Proc. Natl. Acad. Sci. U.S.A..
8. Lepot, Kevin. (2020). "Signatures of early microbial life from the Archean (4 to 2.5 Ga) eon". Earth-Science Reviews.
9. (15 January 2018). "Isotopic evidence for oxygenated Mesoarchaean shallow oceans". [[Nature Geoscience]].

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