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Mesoarchean

Mesoarchean Eon
3200–2800 million years ago
-4500 —
-4000 —
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The Mesoarchean (/ˌmzɑːrˈkən/, also spelled Mesoarchaean) is a geologic era within the Archean Eon, spanning 3,200 to 2,800 million years ago. The era is defined chronometrically and is not referenced to a specific level in a rock section on Earth. Fossils from Australia show that stromatolites have grown on Earth since the Mesoarchean. The Pongola glaciation occurred around 2,900 million years ago.[1] The first supercontinent Vaalbara broke up during this era about 2,800 million years ago.

The earliest reefs date from this era, and were probably formed by stromatolites[2][3]. Analysis of oxygen isotopes in cherts led to an oceanic temperature estimate around 55-85º C [4], while other studies of weathering rates postulate average temperatures below 50º C[5]. Dinitrogen content in the atmosphere is thought to have been fundamentally similar to today's, and the partial pressure of carbon dioxide was probably lower than 0.7 bar[6].

See also

References

  1. ^ Robert E. Kopp; Joseph L. Kirschvink; Isaac A. Hilburn & Cody Z. Nash (2005). "The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis". Proc. Natl. Acad. Sci. U.S.A. 102 (32): 11131–6. Bibcode:2005PNAS..10211131K. doi:10.1073/pnas.0504878102. PMC 1183582. PMID 16061801.
  2. ^ Allwood, Abigail C.; Walter, Malcolm R.; Kamber, Balz S.; Marshall, Craig P.; Burch, Ian W. (8 June 2006). "Stromatolite reef from the Early Archaean era of Australia". Nature. 441 (7094): 714–718. Bibcode:2006Natur.441..714A. doi:10.1038/nature04764. Retrieved 10 March 2018.
  3. ^ Nelson, Jon (15 April 1997). "Stromatolites: Our Mysterious Ancient Reefs". Lake Superior Magazine. Retrieved 10 March 2018.
  4. ^ Knauth, L. P. Lowe, D. R. High Archean climatic temperature inferred from oxygen isotope geochemistry of cherts in the 3.5 Ga Swaziland group, South Africa, Geol. Soc. Amer. Bull. 115 (2003) 566 – 580.
  5. ^ Sleep, Norman H.; Hessler, Angela M. (January 2006). "Weathering of quartz as an Archean climatic indicator" (PDF). Earth and Planetary Science Letters. 241 (3–4): 594–602. Bibcode:2006E&PSL.241..594S. doi:10.1016/j.epsl.2005.11.020. Retrieved 10 March 2018.
  6. ^ Marty, Bernard; Zimmermann, Laurent; Pujol, Magali; Burgess, Ray; Philippot, Pascal (4 October 2013). "Nitrogen Isotopic Composition and Density of the Archean Atmosphere". Science. 342 (6154): 101–104. arXiv:1405.6337. Bibcode:2013Sci...342..101M. doi:10.1126/science.1240971. ISSN 0036-8075. Retrieved 10 March 2018.

External links