Archean

Not to be confused with Archaea.

The Archean Eon (IPA: /ɑːrˈkiːən/ ar-KEE-ən, also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history, preceded by the Hadean Eon and followed by the Proterozoic. The Archean represents the time period from 4,031 to 2,500 Ma (millions of years ago). The Late Heavy Bombardment is hypothesized to overlap with the beginning of the Archean. The Huronian glaciation occurred at the end of the eon.

Archean
4031 ± 3 – 2500 Ma Pha. Proterozoic Archean Had.
Artist's impression of an Archean landscape.
Chronology
−4500 — – — – −4000 — – — – −3500 — – — – −3000 — – — – −2500 — – — – −2000 — – — – −1500 — – — – −1000 — – — – −500 — – — – 0 — P r e c a m b r i a n Hadean A r c h e a n P r o t e r o z o i c P h a n. Eo Paleo Meso Neo Paleo Meso Neo Paleozoic Mesozoic Cenozoic   Scale: millions of years
Etymology
Name formality	Formal
Alternate spelling(s)	Archaean, Archæan
Synonym(s)	Eozoic J.W. Dawson, 1865
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Eon
Stratigraphic unit	Eonothem
Time span formality	Formal
Lower boundary definition	Ten oldest U-Pb zircon ages
Lower boundary GSSA	Along the Acasta River, Northwest Territories, Canada 65°10′26″N 115°33′14″W / 65.1738°N 115.5538°W / 65.1738; -115.5538
Lower GSSA ratified	2023^[1]
Upper boundary definition	Defined Chronometrically
Upper GSSA ratified	1991^[2]

The Earth during the Archean was mostly a water world: there was continental crust, but much of it was under an ocean deeper than today's oceans. Except for some trace minerals, today's oldest continental crust dates back to the Archean. Much of the geological detail of the Archean has been destroyed by subsequent activity. The Earth's atmosphere was also vastly different in composition to today's: it was a reducing atmosphere rich in methane and lacking free oxygen.

The earliest known life, mostly represented by shallow-water microbial mats called stromatolites, started in the Archean and remained simple prokaryotes (archaea and eubacteria) throughout the eon. The earliest photosynthetic processes, especially those by early cyanobacteria, appeared in the mid/late Archean and led to a permanent chemical change in the ocean and the atmosphere after the Archean.

Etymology and changes in classification

The word Archean is derived from the Greek word arkhē (αρχή), meaning 'beginning, origin'.^[3] The Pre-Cambrian eon had been believed to be without life (azoic); however, fossils were found in deposits that were judged to belong to the Azoic age. Before the Hadean Eon was recognized, the Archean spanned Earth's early history from its formation about 4,540 million years ago until 2,500 million years ago.

Instead of being based on stratigraphy, the beginning and end of the Archean Eon are defined chronometrically. The eon's lower boundary or starting point of 4,031±3 million years ago is officially recognized by the International Commission on Stratigraphy.^[1]

Geology

When the Archean began, the Earth's heat flow was nearly three times as high as it is today, and it was still twice the current level at the transition from the Archean to the Proterozoic (2,500 Ma). The extra heat was partly remnant heat from planetary accretion, from the formation of the metallic core, and partly arose from the decay of radioactive elements. As a result, the Earth's mantle was significantly hotter than today.^[4]

 

The evolution of Earth's radiogenic heat flow over time

Although a few mineral grains are known to be Hadean, the oldest rock formations exposed on the surface of the Earth are Archean. Archean rocks are found in Greenland, Siberia, the Canadian Shield, Montana, Wyoming (exposed parts of the Wyoming Craton), Minnesota (Minnesota River Valley), the Baltic Shield, the Rhodope Massif, Scotland, India, Brazil, western Australia, and southern Africa.^{[citation needed]} Granitic rocks predominate throughout the crystalline remnants of the surviving Archean crust. These include great melt sheets and voluminous plutonic masses of granite, diorite, layered intrusions, anorthosites and monzonites known as sanukitoids. Archean rocks are often heavily metamorphized deep-water sediments, such as graywackes, mudstones, volcanic sediments, and banded iron formations. Volcanic activity was considerably higher than today, with numerous lava eruptions, including unusual types such as komatiite.^[5] Carbonate rocks are rare, indicating that the oceans were more acidic, due to dissolved carbon dioxide, than during the Proterozoic.^[6] Greenstone belts are typical Archean formations, consisting of alternating units of metamorphosed mafic igneous and sedimentary rocks, including Archean felsic volcanic rocks. The metamorphosed igneous rocks were derived from volcanic island arcs, while the metamorphosed sediments represent deep-sea sediments eroded from the neighboring island arcs and deposited in a forearc basin. Greenstone belts, which include both types of metamorphosed rock, represent sutures between the protocontinents.^{[7]: 302–303}

Plate tectonics likely started vigorously in the Hadean, but slowed down in the Archean.^[8][9] The slowing of plate tectonics was probably due to an increase in the viscosity of the mantle due to outgassing of its water.^[8] Plate tectonics likely produced large amounts of continental crust, but the deep oceans of the Archean probably covered the continents entirely.^[10] Only at the end of the Archean did the continents likely emerge from the ocean.^[11]

Due to recycling and metamorphosis of the Archean crust, there is a lack of extensive geological evidence for specific continents. One hypothesis is that rocks that are now in India, western Australia, and southern Africa formed a continent called Ur as of 3,100 Ma.^[12] Another hypothesis, which conflicts with the first, is that rocks from western Australia and southern Africa were assembled in a continent called Vaalbara as far back as 3,600 Ma.^[13] Archean rock makes up only about 8% of Earth's present-day continental crust; the rest of the Archean continents have been recycled.^[8]

By the Neoarchean, plate tectonic activity may have been similar to that of the modern Earth, although there was a significantly greater occurrence of slab detachment resulting from a hotter mantle, rheologically weaker plates, and increased tensile stresses on subducting plates due to their crustal material metamorphosing from basalt into eclogite as they sank.^[14][15] There are well-preserved sedimentary basins, and evidence of volcanic arcs, intracontinental rifts, continent-continent collisions and widespread globe-spanning orogenic events suggesting the assembly and destruction of one and perhaps several supercontinents. Evidence from banded iron formations, chert beds, chemical sediments and pillow basalts demonstrates that liquid water was prevalent and deep oceanic basins already existed.

Asteroid impacts were frequent in the early Archean.^[16] Evidence from spherule layers suggests that impacts continued into the later Archean, at an average rate of about one impactor with a diameter greater than 10 kilometers (6 mi) every 15 million years. This is about the size of the Chicxulub impactor. These impacts would have been an important oxygen sink and would have caused drastic fluctuations of atmospheric oxygen levels.^[17]

Environment

 

The pale orange dot, an artist's impression of the early Earth which is believed to have appeared orange through its hazy, methane rich, prebiotic second atmosphere. Earth's atmosphere at this stage was somewhat comparable to today's atmosphere of Titan.^[18]

The Archean atmosphere is thought to have almost completely lacked free oxygen; oxygen levels were less than 0.001% of their present atmospheric level,^[19][20] with some analyses suggesting they were as low as 0.00001% of modern levels.^[21] However, transient episodes of heightened oxygen concentrations are known from this eon around 2,980–2,960 Ma,^[22] 2,700 Ma,^[23] and 2,501 Ma.^[24][25] The pulses of increased oxygenation at 2,700 and 2,501 Ma have both been considered by some as potential start points of the Great Oxygenation Event,^[23][26] which most scholars consider to have begun in the Palaeoproterozoic.^[27][28][29] Furthermore, oases of relatively high oxygen levels existed in some nearshore shallow marine settings by the Mesoarchean.^[30] The ocean was broadly reducing and lacked any persistent redoxcline, a water layer between oxygenated and anoxic layers with a strong redox gradient, which would become a feature in later, more oxic oceans.^[31] Despite the lack of free oxygen, the rate of organic carbon burial appears to have been roughly the same as in the present.^[32] Due to extremely low oxygen levels, sulphate was rare in the Archean ocean, and sulphides were produced primarily through reduction of organically sourced sulphite or through mineralisation of compounds containing reduced sulphur.^[33] The Archean ocean was enriched in heavier oxygen isotopes relative to the modern ocean, though δ18O values decreased to levels comparable to those of modern oceans over the course of the later part of the eon as a result of increased continental weathering.^[34]

Astronomers think that the Sun had about 75–80 percent of its present luminosity,^[35] yet temperatures on Earth appear to have been near modern levels only 500 million years after Earth's formation (the faint young Sun paradox). The presence of liquid water is evidenced by certain highly deformed gneisses produced by metamorphism of sedimentary protoliths. The moderate temperatures may reflect the presence of greater amounts of greenhouse gases than later in the Earth's history.^[36][37][38] Extensive abiotic denitrification took place on the Archean Earth, pumping the greenhouse gas nitrous oxide into the atmosphere.^[39] Alternatively, Earth's albedo may have been lower at the time, due to less land area and cloud cover.^[40]

Early life

Main article: Earliest known life forms

For details on how life got started, see Abiogenesis.

The processes that gave rise to life on Earth are not completely understood, but there is substantial evidence that life came into existence either near the end of the Hadean Eon or early in the Archean Eon.

The earliest evidence for life on Earth is graphite of biogenic origin found in 3.7 billion–year-old metasedimentary rocks discovered in Western Greenland.^[41]

 

Lithified stromatolites on the shores of Lake Thetis, Western Australia. Archean stromatolites are the first direct fossil traces of life on Earth.

The earliest identifiable fossils consist of stromatolites, which are microbial mats formed in shallow water by cyanobacteria. The earliest stromatolites are found in 3.48 billion-year-old sandstone discovered in Western Australia.^[42][43] Stromatolites are found throughout the Archean^[44] and become common late in the Archean.^[7]: 307 Cyanobacteria were instrumental in creating free oxygen in the atmosphere.^{[citation needed]}

Further evidence for early life is found in 3.47 billion-year-old baryte, in the Warrawoona Group of Western Australia. This mineral shows sulfur fractionation of as much as 21.1%,^[45] which is evidence of sulfate-reducing bacteria that metabolize sulfur-32 more readily than sulfur-34.^[46]

Evidence of life in the Late Hadean is more controversial. In 2015, biogenic carbon was detected in zircons dated to 4.1 billion years ago, but this evidence is preliminary and needs validation.^[47][48]

Earth was very hostile to life before 4,300 to 4,200 Ma, and the conclusion is that before the Archean Eon, life as we know it would have been challenged by these environmental conditions. While life could have arisen before the Archean, the conditions necessary to sustain life could not have occurred until the Archean Eon.^[49]

Life in the Archean was limited to simple single-celled organisms (lacking nuclei), called prokaryotes. In addition to the domain Bacteria, microfossils of the domain Archaea have also been identified. There are no known eukaryotic fossils from the earliest Archean, though they might have evolved during the Archean without leaving any.^{[7]: 306, 323} Fossil steranes, indicative of eukaryotes, have been reported from Archean strata but were shown to derive from contamination with younger organic matter.^[50] No fossil evidence has been discovered for ultramicroscopic intracellular replicators such as viruses.

Fossilized microbes from terrestrial microbial mats show that life was already established on land 3.22 billion years ago.^[51][52]

See also

• Abiogenesis – Natural process by which life arises from non-living matter
• Cosmic Calendar – Method to visualize the chronology of the universe
• Earliest known life forms – Putative fossilized microorganisms found near hydrothermal vents
• Geologic time scale – System that relates geologic strata to time
• Geological history of oxygen – Timeline of the development of free oxygen in the Earth's seas and atmosphere
• History of Earth – Development of planet Earth from its formation to the present day
• Precambrian – History of Earth 4600–539 million years ago
• Timeline of natural history
• Archean felsic volcanic rocks – Felsic volcanic rocks formed in the Archean Eon

References

1. "Global Boundary Stratotype Section and Point". International Commission of Stratigraphy. Retrieved 29 October 2023.
2. Plumb, K. A. (1 June 1991). "New Precambrian time scale". Episodes. 14 (2): 139–140. doi:10.18814/epiiugs/1991/v14i2/005.
3. Harper, Douglas. "Archaean". Online Etymology Dictionary.
4. Galer, Stephen J. G.; Mezger, Klaus (1 December 1998). "Metamorphism, denudation and sea level in the Archean and cooling of the Earth". Precambrian Research. 92 (4): 389–412. Bibcode:1998PreR...92..389G. doi:10.1016/S0301-9268(98)00083-7. Retrieved 24 November 2022.
5. Dostal J (2008). "Igneous Rock Associations 10. Komatiites". Geoscience Canada. 35 (1).
6. Cooper, John D.; Miller, Richard H.; Patterson, Jacqueline (1986). A Trip Through Time: Principles of historical geology. Columbus: Merrill Publishing Company. p. 180. ISBN 978-0675201407.
7. Stanley, Steven M. (1999). Earth System History. New York: W.H. Freeman and Company. ISBN 978-0716728825.
8. Korenaga, J (2021). "Was There Land on the Early Earth?". Life. 11 (11): 1142. Bibcode:2021Life...11.1142K. doi:10.3390/life11111142. PMC 8623345. PMID 34833018.
9. Korenaga, J (2021). "Hadean geodynamics and the nature of early continental crust". Precambrian Res. 359: 106178. Bibcode:2021PreR..359j6178K. doi:10.1016/j.precamres.2021.106178. S2CID 233441822.
10. Bada, JL; Korenaga, J (2018). "Exposed areas above sea level on Earth >3.5 Gyr ago: Implications for prebiotic and primitive biotic chemistry". Life. 8 (4): 55. Bibcode:2018Life....8...55B. doi:10.3390/life8040055. PMC 6316429. PMID 30400350.
11. Bindeman, IN; Zakharov, DO; Palandri, J.; Greber, ND; et al. (2018). "Rapid emergence of subaerial landmasses and onset of a modern hydrologic cycle 2.5 billion years ago". Nature. 557 (7706): 545–548. Bibcode:2018Natur.557..545B. doi:10.1038/s41586-018-0131-1. PMID 29795252. S2CID 43921922.
12. Rogers JJ (1996). "A history of continents in the past three billion years". Journal of Geology. 104 (1): 91–107. Bibcode:1996JG....104...91R. doi:10.1086/629803. JSTOR 30068065. S2CID 128776432.
13. Cheney ES (1996). "Sequence stratigraphy and plate tectonic significance of the Transvaal succession of southern Africa and its equivalent in Western Australia". Precambrian Research. 79 (1–2): 3–24. Bibcode:1996PreR...79....3C. doi:10.1016/0301-9268(95)00085-2.
14. Marty, Bernard; Dauphas, Nicolas (15 February 2003). "The nitrogen record of crust–mantle interaction and mantle convection from Archean to Present". Earth and Planetary Science Letters. 206 (3–4): 397–410. Bibcode:2003E&PSL.206..397M. doi:10.1016/S0012-821X(02)01108-1. Retrieved 16 November 2022.
15. Halla, Jaana; Van Hunen, Jeroen; Heilimo, Esa; Hölttä, Pentti (October 2009). "Geochemical and numerical constraints on Neoarchean plate tectonics". Precambrian Research. 174 (1–2): 155–162. Bibcode:2009PreR..174..155H. doi:10.1016/j.precamres.2009.07.008. Retrieved 12 November 2022.
16. Borgeat, Xavier; Tackley, Paul J. (12 July 2022). "Hadean/Eoarchean tectonics and mantle mixing induced by impacts: a three-dimensional study". Progress in Earth and Planetary Science. 9 (1): 38. Bibcode:2022PEPS....9...38B. doi:10.1186/s40645-022-00497-0. hdl:20.500.11850/559385. S2CID 243973728.
17. Marchi, S.; Drabon, N.; Schulz, T.; Schaefer, L.; Nesvorny, D.; Bottke, W. F.; Koeberl, C.; Lyons, T. (November 2021). "Delayed and variable late Archaean atmospheric oxidation due to high collision rates on Earth". Nature Geoscience. 14 (11): 827–831. Bibcode:2021NatGe..14..827M. doi:10.1038/s41561-021-00835-9. S2CID 239055744.
18. Trainer, Melissa G.; Pavlov, Alexander A.; DeWitt, H. Langley; Jimenez, Jose L.; McKay, Christopher P.; Toon, Owen B.; Tolbert, Margaret A. (28 November 2006). "Organic haze on Titan and the early Earth". Proceedings of the National Academy of Sciences of the United States of America. 103 (48): 18035–18042. doi:10.1073/pnas.0608561103. ISSN 0027-8424. PMC 1838702. PMID 17101962.
19. Pavlov, A. A.; Kasting, J. F. (5 July 2004). "Mass-Independent Fractionation of Sulfur Isotopes in Archean Sediments: Strong Evidence for an Anoxic Archean Atmosphere". Astrobiology. 2 (1): 27–41. doi:10.1089/153110702753621321. PMID 12449853. Retrieved 12 November 2022.
20. Zhang, Shuichang; Wang, Xiaomei; Wang, Huajian; Bjerrum, Christian J.; Hammarlund, Emma U.; Costa, M. Mafalda; Connelly, James N.; Zhang, Baomin; Su, Jin; Canfield, Donald Eugene (4 January 2016). "Sufficient oxygen for animal respiration 1,400 million years ago". Proceedings of the National Academy of Sciences of the United States of America. 113 (7): 1731–1736. Bibcode:2016PNAS..113.1731Z. doi:10.1073/pnas.1523449113. PMC 4763753. PMID 26729865.
21. Laakso, T. A.; Schrag, D. P. (5 April 2017). "A theory of atmospheric oxygen". Geobiology. 15 (3): 366–384. Bibcode:2017Gbio...15..366L. doi:10.1111/gbi.12230. PMID 28378894. S2CID 22594748. Retrieved 12 November 2022.
22. Crowe, Sean A.; Døssing, Lasse N.; Beukes, Nicolas J.; Bau, Michael; Kruger, Stephanus J.; Frei, Robert; Canfield, Donald Eugene (25 September 2013). "Atmospheric oxygenation three billion years ago". Nature. 501 (7468): 535–538. Bibcode:2013Natur.501..535C. doi:10.1038/nature12426. PMID 24067713. S2CID 4464710. Retrieved 12 November 2022.
23. Large, Ross R.; Hazen, Robert M.; Morrison, Shaunna M.; Gregory, Dan D.; Steadman, Jeffrey A.; Mukherjee, Indrani (May 2022). "Evidence that the GOE was a prolonged event with a peak around 1900 Ma". Geosystems and Geoenvironment. 1 (2): 100036. Bibcode:2022GsGe....100036L. doi:10.1016/j.geogeo.2022.100036. S2CID 246755121. Retrieved 7 January 2023.
24. Anbar, Ariel D.; Duan, Yun; Lyons, Timothy W.; Arnold, Gail N.; Kendall, Brian; Creaser, Robert A.; Kaufman, Alan J.; Gordon, Gwyneth W.; Scott, Clinton; Garvin, Jessica; Buick, Roger (28 September 2007). "A Whiff of Oxygen Before the Great Oxidation Event?". Science. 317 (5846): 1903–1906. Bibcode:2007Sci...317.1903A. doi:10.1126/science.1140325. PMID 17901330. S2CID 25260892. Retrieved 12 November 2022.
25. Reinhard, Christopher T.; Raiswell, Robert; Scott, Clinton; Anbar, Ariel D.; Lyons, Timothy W. (30 October 2009). "A Late Archean Sulfidic Sea Stimulated by Early Oxidative Weathering of the Continents". Science. 326 (5953): 713–716. Bibcode:2009Sci...326..713R. doi:10.1126/science.1176711. PMID 19900929. S2CID 25369788. Retrieved 12 November 2022.
26. Warke, Matthew R.; Di Rocco, Tommaso; Zerkle, Aubrey L.; Lepland, Aivo; Prave, Anthony R.; Martin, Adam P.; Ueno, Yuichiro; Condon, Daniel J.; Claire, Mark W. (16 June 2020). "The Great Oxidation Event preceded a Paleoproterozoic "snowball Earth"". Proceedings of the National Academy of Sciences of the United States of America. 117 (24): 13314–13320. Bibcode:2020PNAS..11713314W. doi:10.1073/pnas.2003090117. ISSN 0027-8424. PMC 7306805. PMID 32482849.
27. Luo, Genming; Ono, Shuhei; Beukes, Nicolas J.; Wang, David T.; Xie, Shucheng; Summons, Roger E. (6 May 2016). "Rapid oxygenation of Earth's atmosphere 2.33 billion years ago". Science Advances. 2 (5): e1600134. Bibcode:2016SciA....2E0134L. doi:10.1126/sciadv.1600134. ISSN 2375-2548. PMC 4928975. PMID 27386544.
28. Poulton, Simon W.; Bekker, Andrey; Cumming, Vivien M.; Zerkle, Aubrey L.; Canfield, Donald E.; Johnston, David T. (April 2021). "A 200-million-year delay in permanent atmospheric oxygenation". Nature. 592 (7853): 232–236. Bibcode:2021Natur.592..232P. doi:10.1038/s41586-021-03393-7. ISSN 1476-4687. PMID 33782617. S2CID 232419035. Retrieved 7 January 2023.
29. Gumsley, Ashley P.; Chamberlain, Kevin R.; Bleeker, Wouter; Söderlund, Ulf; De Kock, Michiel O.; Larsson, Emilie R.; Bekker, Andrey (6 February 2017). "Timing and tempo of the Great Oxidation Event". Proceedings of the National Academy of Sciences of the United States of America. 114 (8): 1811–1816. Bibcode:2017PNAS..114.1811G. doi:10.1073/pnas.1608824114. ISSN 0027-8424. PMC 5338422. PMID 28167763.
30. Eickmann, Benjamin; Hofmann, Axel; Wille, Martin; Bui, Thi Hao; Wing, Boswell A.; Schoenberg, Ronny (15 January 2018). "Isotopic evidence for oxygenated Mesoarchaean shallow oceans". Nature Geoscience. 11 (2): 133–138. Bibcode:2018NatGe..11..133E. doi:10.1038/s41561-017-0036-x. S2CID 135023426. Retrieved 25 December 2022.
31. Zhou, Hang; Zhou, Wenxiao; Wei, Yunxu; Chi Fru, Ernest; Huang, Bo; Fu, Dong; Li, Haiquan; Tan, Mantang (December 2022). "Mesoarchean banded iron-formation from the northern Yangtze Craton, South China and its geological and paleoenvironmental implications". Precambrian Research. 383: 106905. doi:10.1016/j.precamres.2022.106905. Retrieved 17 December 2022.
32. Fischer, W. W.; Schroeder, S.; Lacassie, J. P.; Beukes, N. J.; Goldberg, T.; Strauss, H.; Horstmann, U. E.; Schrag, D. P.; Knoll, A. H. (March 2009). "Isotopic constraints on the Late Archean carbon cycle from the Transvaal Supergroup along the western margin of the Kaapvaal Craton, South Africa". Precambrian Research. 169 (1–4): 15–27. Bibcode:2009PreR..169...15F. doi:10.1016/j.precamres.2008.10.010. Retrieved 24 November 2022.
33. Fakhraee, Mojtaba; Katsev, Sergei (7 October 2019). "Organic sulfur was integral to the Archean sulfur cycle". Nature Communications. 10 (1): 4556. Bibcode:2019NatCo..10.4556F. doi:10.1038/s41467-019-12396-y. PMC 6779745. PMID 31591394.
34. Johnson, Benjamin W.; Wing, Boswell A. (2 March 2020). "Limited Archaean continental emergence reflected in an early Archaean 18O-enriched ocean". Nature Geoscience. 13 (3): 243–248. Bibcode:2020NatGe..13..243J. doi:10.1038/s41561-020-0538-9. S2CID 211730235. Retrieved 7 January 2023.
35. Dauphas, Nicolas; Kasting, James Fraser (1 June 2011). "Low pCO2 in the pore water, not in the Archean air". Nature. 474 (7349): E2-3, discussion E4-5. Bibcode:2011Natur.474E...1D. doi:10.1038/nature09960. PMID 21637211. S2CID 205224575.
36. Walker, James C. G. (November 1982). "Climatic factors on the Archean earth". Palaeogeography, Palaeoclimatology, Palaeoecology. 40 (1–3): 1–11. Bibcode:1982PPP....40....1W. doi:10.1016/0031-0182(82)90082-7. hdl:2027.42/23810. Retrieved 12 November 2022.
37. Walker, James C.G. (June 1985). "Carbon dioxide on the early earth" (PDF). Origins of Life and Evolution of Biospheres. 16 (2): 117–127. Bibcode:1985OrLi...16..117W. doi:10.1007/BF01809466. hdl:2027.42/43349. PMID 11542014. S2CID 206804461. Retrieved 30 January 2010.
38. Pavlov AA, Kasting JF, Brown LL, Rages KA, Freedman R (May 2000). "Greenhouse warming by CH₄ in the atmosphere of early Earth". Journal of Geophysical Research. 105 (E5): 11981–11990. Bibcode:2000JGR...10511981P. doi:10.1029/1999JE001134. PMID 11543544.
39. Buessecker, Steffen; Imanaka, Hiroshi; Ely, Tucker; Hu, Renyu; Romaniello, Stephen J.; Cadillo-Quiroz, Hinsby (5 December 2022). "Mineral-catalysed formation of marine NO and N2O on the anoxic early Earth". Nature Geoscience. 15 (1): 1056–1063. Bibcode:2022NatGe..15.1056B. doi:10.1038/s41561-022-01089-9. S2CID 254276951. Retrieved 28 April 2023.
40. Rosing MT, Bird DK, Sleep NH, Bjerrum CJ (April 2010). "No climate paradox under the faint early Sun". Nature. 464 (7289): 744–747. Bibcode:2010Natur.464..744R. doi:10.1038/nature08955. PMID 20360739. S2CID 205220182.
41. Ohtomo Y, Kakegawa T, Ishida A, Nagase T, Rosing MT (8 December 2013). "Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks". Nature Geoscience. 7 (1): 25–28. Bibcode:2014NatGe...7...25O. doi:10.1038/ngeo2025.
42. Borenstein, Seth (13 November 2013). "Oldest fossil found: Meet your microbial mom". AP News. Retrieved 15 November 2013.
43. Noffke N, Christian D, Wacey D, Hazen RM (December 2013). "Microbially induced sedimentary structures recording an ancient ecosystem in the ca. 3.48 billion-year-old Dresser Formation, Pilbara, Western Australia". Astrobiology. 13 (12): 1103–1124. Bibcode:2013AsBio..13.1103N. doi:10.1089/ast.2013.1030. PMC 3870916. PMID 24205812.
44. Garwood, Russell J. (2012). "Patterns In Palaeontology: The first 3 billion years of evolution". Palaeontology Online. 2 (11): 1–14. Retrieved 25 June 2015.
45. Shen Y, Buick R, Canfield DE (March 2001). "Isotopic evidence for microbial sulphate reduction in the early Archaean era". Nature. 410 (6824): 77–81. Bibcode:2001Natur.410...77S. doi:10.1038/35065071. PMID 11242044. S2CID 25375808.
46. Seal RR (2006). "Sulfur isotope geochemistry of sulfide minerals". Reviews in Mineralogy and Geochemistry. 61 (1): 633–677. Bibcode:2006RvMG...61..633S. doi:10.2138/rmg.2006.61.12.
47. Borenstein, Seth (19 October 2015). "Hints of life on what was thought to be desolate early Earth". Excite. Yonkers, NY: Mindspark Interactive Network. Associated Press. Retrieved 20 October 2015.
48. Bell EA, Boehnke P, Harrison TM, Mao WL (November 2015). "Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon". Proceedings of the National Academy of Sciences of the United States of America (Early, published online before print ed.). 112 (47): 14518–14521. Bibcode:2015PNAS..11214518B. doi:10.1073/pnas.1517557112. PMC 4664351. PMID 26483481.
49. Nisbet, Euan (1980). "Archaean stromatolites and the search for the earliest life". Nature. 284 (5755): 395–396. Bibcode:1980Natur.284..395N. doi:10.1038/284395a0. S2CID 4262249.
50. French KL, Hallmann C, Hope JM, Schoon PL, Zumberge JA, Hoshino Y, Peters CA, George SC, Love GD, Brocks JJ, Buick R, Summons RE (May 2015). "Reappraisal of hydrocarbon biomarkers in Archean rocks". Proceedings of the National Academy of Sciences of the United States of America. 112 (19): 5915–5920. Bibcode:2015PNAS..112.5915F. doi:10.1073/pnas.1419563112. PMC 4434754. PMID 25918387.
51. Homann, Martin; Sansjofre, Pierre; Van Zuilen, Mark; Heubeck, Christoph; Gong, Jian; Killingsworth, Bryan; Foster, Ian S.; Airo, Alessandro; Van Kranendonk, Martin J.; Ader, Magali; Lalonde, Stefan V. (23 July 2018). "Microbial life and biogeochemical cycling on land 3,220 million years ago". Nature Geoscience. 11 (9): 665–671. Bibcode:2018NatGe..11..665H. doi:10.1038/s41561-018-0190-9. S2CID 134935568. Retrieved 14 January 2023.
52. Woo, Marcus (30 July 2018). "Oldest Evidence for life on land unearthed in South Africa". livescience.com.

External links

• . GeoWhen Database. stratigraphy.org. Archived from the original on 22 August 2010. Retrieved 17 September 2010.
• "When did plate tectonics begin?". utdallas.edu. University of Texas – Dallas.
• "Archean (chronostratigraphy scale)". ghkclass.com.