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The Eoarchean
Eoarchean
( /ˌiːoʊ.ɑːrˈkiːən/; also spelled Eoarchaean) is the first era of the Archean
Archean
Eon of the geologic record for which the Earth has a solid crust. It spans 400 million years from the end of the Hadean
Hadean
Eon 4 billion years ago (4000 Mya) to the start of the Paleoarchean
Paleoarchean
Era 3600 Mya. The beginnings of life on Earth have been dated to this era and evidence of cyanobacteria date to 3500 Mya, just outside this era. At that time, the atmosphere was without oxygen and the pressure values ranged from 10 to 100 bar (around 10 to 100 atmospheres).[1][2][3]

Contents

1 Chronology 2 Geology 3 Atmosphere 4 Proposed subdivisions 5 See also 6 References 7 Further reading 8 External links

Chronology[edit] The Eoarchean
Eoarchean
was formerly officially unnamed and informally referred to as the first part of the Early Archean
Archean
or Paleoarchean
Paleoarchean
Era, both now obsolete names. The International Commission on Stratigraphy now officially recognizes the Eoarchean
Eoarchean
Era as the first part of the Archaean Eon, preceded by the Hadean
Hadean
Eon, during which the Earth is believed to have been essentially molten. The Eoarchaean's lower boundary or starting point of 4 Gya (4 billion years ago) is officially recognized by the International Commission on Stratigraphy.[4] The name comes from two Greek words: eos (dawn) and archaios (ancient). The first supercontinent Vaalbara
Vaalbara
appeared around the end of this period at about 3,600 million years ago.

Geology[edit] Main article: Eoarchean
Eoarchean
geology A characteristic of the Eoarchean
Eoarchean
is that Earth possessed a firm crust for the first time. However, this crust may have been incomplete at many sites and areas of lava may have existed at the surface. The beginning of the Eoarchean
Eoarchean
is characterized by heavy asteroid bombardment within the inner solar system: the Late Heavy Bombardment. The largest Eoarchean
Eoarchean
rock formation is the Isua Greenstone Belt
Isua Greenstone Belt
on the south-west coast of Greenland and dates from 3.8 billion years. The Acasta Gneiss
Acasta Gneiss
within the Canadian Shield
Canadian Shield
have been dated to be 4,031 Ma and are therefore the oldest preserved rock formations. In 2008, another rock formation was discovered in the Nuvvuagittuq greenstone belt in northern Québec
Québec
Canada which has been dated to be 4,280 million years ago.[5] These formations are presently under intense investigation.[6]

Atmosphere[edit] 3,850 million years old Greenland apatite shows evidence of 12C enrichment. This has sparked a debate whether there might have been photosynthetic life before 3.8 billion years.[7]

Proposed subdivisions[edit] Eoarchean
Eoarchean
Era — 4031–3600 MYA Acastan Period — 4031–3810 MYA Isuan
Isuan
Period — 3810–3600 MYA[8] See also[edit] Precambrian
Precambrian
Supereon (4600-542 MYA) Hadean
Hadean
Eon (4600-4000 MYA) Archean
Archean
Eon (4000-2500 MYA) Paleoarchean
Paleoarchean
Era (3600-3200 MYA) Mesoarchean Era (3200-2800 MYA) Neoarchean Era (2800-2500 MYA) Proterozoic
Proterozoic
Eon (2500-542 MYA) References[edit]

^ Mulkidjanian, A. Y. (2009). "On the origin of life in the zinc world: 1. Photosynthesizing, porous edifices built of hydrothermally precipitated zinc sulfide as cradles of life on Earth". Biol. Direct. 4: 26. doi:10.1186/1745-6150-4-26. PMC 3152778. PMID 19703272..mw-parser-output cite.citation font-style:inherit .mw-parser-output .citation q quotes:"""""""'""'" .mw-parser-output .citation .cs1-lock-free a background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center .mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration a background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center .mw-parser-output .citation .cs1-lock-subscription a background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center .mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration color:#555 .mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span border-bottom:1px dotted;cursor:help .mw-parser-output .cs1-ws-icon a background:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center .mw-parser-output code.cs1-code color:inherit;background:inherit;border:inherit;padding:inherit .mw-parser-output .cs1-hidden-error display:none;font-size:100% .mw-parser-output .cs1-visible-error font-size:100% .mw-parser-output .cs1-maint display:none;color:#33aa33;margin-left:0.3em .mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format font-size:95% .mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left padding-left:0.2em .mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right padding-right:0.2em

^ Mulkidjanian, A. Y.; Bychkov, A. Y.; Dibrova, D. V.; Galperin, M. Y.; Koonin, E. V. (2012). "Origin of first cells at terrestrial, anoxic geothermal fields". Proc. Natl. Acad. Sci. USA. 109 (14): E821–30. Bibcode:2012PNAS..109E.821M. doi:10.1073/pnas.1117774109. PMC 3325685. PMID 22331915.

^ Mulkidjanian, A. Y. (2011). "Energetics of the First Life". In Egel, R.; Lankenau, D.-H.; Mulkidjanian, A. Y. (eds.). Origins of Life: The Primal Self-Organization. Heidelberg: Springer Verlag. pp. 3–33. ISBN 978-3-642-21625-1.

^ "International Chronostratigraphic Chart v.2013/01" (PDF). International Commission on Stratigraphy. January 2013. Retrieved April 6, 2013.

^ O'Neil, J.; Carlson, R. W.; Francis; D.; Stevenson, R. K. (2008). "Neodymium-142 Evidence for Hadean
Hadean
Mafic Crust". Science. 321 (5897): 1828–1831. Bibcode:2008Sci...321.1828O. doi:10.1126/science.1161925. PMID 18818357.

^ David, J.; Godin, L.; Stevenson, R. K.; O'Neil, J.; Francis, D. (2009). "U-Pb ages (3.8–2.7 Ga) and Nd isotope data from the newly identified Eoarchean
Eoarchean
Nuvvuagittuq supracrustal belt, Superior Craton, Canada". Geological Society of America Bulletin. 121 (1–2): 150–163. doi:10.1130/B26369.1.

^ Mojzsis, S. J.; Arrhenius, G.; McKeegan, K. D.; Harrison, T. M.; Nutman, A. P.; Friend, C. R. L. (1996). "Evidence for life on Earth before 3,800 million years ago" (PDF). Nature. 384 (6604): 55–59. Bibcode:1996Natur.384...55M. doi:10.1038/384055a0. hdl:2060/19980037618. PMID 8900275.

^ Van Kranendonk, Martin J. (2012). "16: A Chronostratigraphic Division of the Precambrian: Possibilities and Challenges". In Felix M. Gradstein; James G. Ogg; Mark D. Schmitz; abi M. Ogg (eds.). The geologic time scale 2012 (1st ed.). Amsterdam: Elsevier. pp. 359–365. ISBN 978-0-44-459425-9.

Further reading[edit] Egel, R.; Lankenau, D.-H.; Mulkidjanian, A. Y. (2011). Origins of Life: The Primal Self-Organization. Berlin Heidelberg: Springer-Verlag. pp. 1–366. doi:10.1007/978-3-642-21625-1. ISBN 978-3-642-21624-4. External links[edit] Media related to Eoarchean
Eoarchean
at Wikimedia Commons Taxonconcept.stratigraphy.ne: A short fact sheet on the Eoarchean Eoarchean
Eoarchean
(chronostratigraphy scale) vte Archean
Archean
Eon Eoarchean Paleoarchean Mesoarchean Neoarchean

vteGeological history of EarthCenozoic era'"`UNIQ--templatestyles-00000014-QINU`"'(present–66.0 Mya) Quaternary
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Lopingian
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Cisuralian
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Carboniferous
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(419.2–443.8 Mya) Pridoli (419.2–423.0 Mya) Ludlow (423.0–427.4 Mya) Wenlock (427.4–433.4 Mya) Llandovery (433.4–443.8 Mya) Ordovician
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Cambrian
(485.4–541.0 Mya) Furongian (485.4–497 Mya) Miaolingian (497–509 Mya) Series 2 (509–521 Mya) Terreneuvian
Terreneuvian
(521–541.0 Mya) Proterozoic
Proterozoic
eon(541.0 Mya–2.5 Gya) Neoproterozoic (541.0 Mya–1 Gya) Ediacaran
Ediacaran
(541.0–~635 Mya) Cryogenian (~635–~720 Mya) Tonian (~720 Mya–1 Gya) Mesoproterozoic (1–1.6 Gya) Stenian (1–1.2 Gya) Ectasian (1.2–1.4 Gya) Calymmian (1.4–1.6 Gya) Paleoproterozoic (1.6–2.5 Gya) Statherian (1.6–1.8 Gya) Orosirian
Orosirian
(1.8–2.05 Gya) Rhyacian (2.05–2.3 Gya) Siderian
Siderian
(2.3–2.5 Gya) Archean
Archean
eon (2.5–4 Gya)Eras Neoarchean (2.5–2.8 Gya) Mesoarchean (2.8–3.2 Gya) Paleoarchean
Paleoarchean
(3.2–3.6 Gya) Eoarchean
Eoarchean
(3.6–4 Gya) Hadean
Hadean
eon (4–4.6 Gya)  kya = thousands years ago. Mya = millions years ago. Gya = billions years ago. See also: Geo

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