Pilbara Craton

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Map of Australia with the Pilbara region highlighted in red.

The Pilbara Craton is an old and stable part of the continental lithosphere located in the Pilbara region of Western Australia.

The Pilbara Craton is one of only two pristine Archaean 3.6–2.7 Ga (billion years ago) crusts identified on the Earth, along with the Kaapvaal Craton in South Africa. Both locations may have once been part of the Vaalbara supercontinent or the continent of Ur.

The eastern portion is called the Eastern Pilbara Craton.

Evidence of earliest life[edit]

In May 2017, evidence of the earliest known life on land may have been found in 3.48-billion-year-old geyserite and other related mineral deposits (often found around hot springs and geysers) uncovered in the Dresser Formation in Pilbara Craton.[1][2][3][4]

The earliest direct evidence of life on Earth may be fossils of microorganisms permineralized in 3.465-billion-year-old Australian Apex chert rocks.[5][6] However, the evidence for the biogenicity of these microstructures has been thoroughly debated. Originally, 11 taxa were described from a deposit thought to be located at the mouth of a river due to certain characteristics like rounded and sorted grains.[7][8] Extensive field mapping and petrogenetic analysis has since shown the setting for the purported microfossils to be hydrothermal[9][10] and this is widely supported.[11][12][13][14] Consequently, many alternative abiotic explanations have been proposed for the filamentous microstructures including carbonaceous rims around quartz spherules and rhombs,[9][10] witherite self-assembled biomorphs[15] and hematite infilled veinlets.[16] The carbonaceous matter composing the filaments has also been repeatedly examined with Raman spectroscopy[9][17][16] which has yielded mixed interpretations of results and is therefore regarded by many to be unreliable for determining biogenicity when used alone.[18][19] Perhaps the most compelling argument to date is based on high spatial resolution electron microscopy like scanning and transmission electron microscopy.[14] This study concludes that the nano-scale morphology of the filaments and the distribution of the carbonaceous matter are inconsistent with a biological origin for the filaments. Instead, it is more likely that the hydrothermal conditions have assisted in the heating, hydration and exfoliation of potassium micas on which barium, iron and carbonate have secondarily been adsorbed.

Additional potential bioindicators from the Precambrian have been found in the region, including carbonaceous microfossils in the northeastern Pilbara Craton.[20]

See also[edit]

References[edit]

  1. ^ Staff (9 May 2017). "Oldest evidence of life on land found in 3.48-billion-year-old Australian rocks". Phys.org. Retrieved 13 May 2017.
  2. ^ Djokic, Tara; Van Kranendonk, Martin J.; Campbell, Kathleen A.; Walter, Malcolm R.; Ward, Colin R. (9 May 2017). "Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits". Nature Communications. 8: 15263. Bibcode:2017NatCo...815263D. doi:10.1038/ncomms15263. PMC 5436104. PMID 28486437.
  3. ^ "Dresser Formation - Pilbara". pilbara.mq.edu.au.
  4. ^ 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): 1103–24. Bibcode:2013AsBio..13.1103N. doi:10.1089/ast.2013.1030. PMC 3870916. PMID 24205812.
  5. ^ Tyrell, Kelly April (18 December 2017). "Oldest fossils ever found show life on Earth began before 3.5 billion years ago". University of Wisconsin-Madison. Retrieved 27 December 2017.
  6. ^ Schopf, J. William; Kitajima, Kouki; Spicuzza, Michael J.; Kudryavtsev, Anatolly B.; Valley, John W. (2017). "SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions". PNAS. 115 (1): 53–58. doi:10.1073/pnas.1718063115. PMC 5776830. PMID 29255053.
  7. ^ Schopf, J.; Packer, B. (3 July 1987). "Early Archean (3.3-billion to 3.5-billion-year-old) microfossils from Warrawoona Group, Australia". Science. 237 (4810): 70–73. Bibcode:1987Sci...237...70S. doi:10.1126/science.11539686. ISSN 0036-8075. PMID 11539686.
  8. ^ Schopf, J. W. (30 April 1993). "Microfossils of the Early Archean Apex Chert: New Evidence of the Antiquity of Life". Science. 260 (5108): 640–646. Bibcode:1993Sci...260..640S. doi:10.1126/science.260.5108.640. ISSN 0036-8075. PMID 11539831. S2CID 2109914.
  9. ^ a b c Brasier, Martin D.; Green, Owen R.; Jephcoat, Andrew P.; Kleppe, Annette K.; Van Kranendonk, Martin J.; Lindsay, John F.; Steele, Andrew; Grassineau, Nathalie V. (March 2002). "Questioning the evidence for Earth's oldest fossils". Nature. 416 (6876): 76–81. Bibcode:2002Natur.416...76B. doi:10.1038/416076a. ISSN 1476-4687. PMID 11882895. S2CID 819491.
  10. ^ a b Brasier, M.; Green, O.; Lindsay, J.; McLoughlin, N.; Steele, A.; Stoakes, C. (21 October 2005). "Critical testing of Earth's oldest putative fossil assemblage from the ∼3.5 Ga Apex chert, Chinaman Creek, Western Australia". Precambrian Research. 140 (1–2): 55–102. Bibcode:2005PreR..140...55B. doi:10.1016/j.precamres.2005.06.008. ISSN 0301-9268.
  11. ^ Vankranendonk, M. (1 February 2006). "Volcanic degassing, hydrothermal circulation and the flourishing of early life on Earth: A review of the evidence from c. 3490-3240 Ma rocks of the Pilbara Supergroup, Pilbara Craton, Western Australia". Earth-Science Reviews. 74 (3–4): 197–240. Bibcode:2006ESRv...74..197V. doi:10.1016/j.earscirev.2005.09.005. ISSN 0012-8252.
  12. ^ Pinti, Daniele L.; Mineau, Raymond; Clement, Valentin (September 2009). "Hydrothermal alteration and microfossil artefacts of the 3,465-million-year-old Apex chert". Nature Geoscience. 2 (9): 640–643. Bibcode:2009NatGe...2..640P. doi:10.1038/ngeo601. ISSN 1752-0908.
  13. ^ Olcott Marshall, Alison; Jehlička, Jan; Rouzaud, Jean-Noel; Marshall, Craig P. (1 January 2014). "Multiple generations of carbonaceous material deposited in Apex chert by basin-scale pervasive hydrothermal fluid flow". Gondwana Research. 25 (1): 284–289. Bibcode:2014GondR..25..284O. doi:10.1016/j.gr.2013.04.006. ISSN 1342-937X.
  14. ^ a b Wacey, David; Saunders, Martin; Kong, Charlie; Brasier, Alexander; Brasier, Martin (1 August 2016). "3.46 Ga Apex chert 'microfossils' reinterpreted as mineral artefacts produced during phyllosilicate exfoliation". Gondwana Research. 36: 296–313. Bibcode:2016GondR..36..296W. doi:10.1016/j.gr.2015.07.010. hdl:2164/9044. ISSN 1342-937X.
  15. ^ Garcia-Ruiz, J. M. (14 November 2003). "Self-Assembled Silica-Carbonate Structures and Detection of Ancient Microfossils". Science. 302 (5648): 1194–1197. Bibcode:2003Sci...302.1194G. doi:10.1126/science.1090163. ISSN 0036-8075. PMID 14615534. S2CID 12117608.
  16. ^ a b Marshall, Craig P.; Emry, Julienne R.; Olcott Marshall, Alison (April 2011). "Haematite pseudomicrofossils present in the 3.5-billion-year-old Apex Chert". Nature Geoscience. 4 (4): 240–243. Bibcode:2011NatGe...4..240M. doi:10.1038/ngeo1084. ISSN 1752-0908.
  17. ^ Schopf, J. William; Kudryavtsev, Anatoliy B.; Agresti, David G.; Wdowiak, Thomas J.; Czaja, Andrew D. (March 2002). "Laser–Raman imagery of Earth's earliest fossils". Nature. 416 (6876): 73–76. Bibcode:2002Natur.416...73S. doi:10.1038/416073a. ISSN 1476-4687. PMID 11882894. S2CID 4382712.
  18. ^ Pasteris, Jill Dill; Wopenka, Brigitte (1 December 2003). "Necessary, but Not Sufficient: Raman Identification of Disordered Carbon as a Signature of Ancient Life". Astrobiology. 3 (4): 727–738. Bibcode:2003AsBio...3..727P. doi:10.1089/153110703322736051. ISSN 1531-1074. PMID 14987478.
  19. ^ Gregorio, Bradley T. De; Sharp, Thomas G. (1 May 2006). "The structure and distribution of carbon in 3.5 Ga Apex chert: Implications for the biogenicity of Earth's oldest putative microfossils". American Mineralogist. 91 (5–6): 784–789. Bibcode:2006AmMin..91..784D. doi:10.2138/am.2006.2149. ISSN 1945-3027. S2CID 129380309.
  20. ^ Sugitani, Kenichiro; et al. (2009). "Taxonomy and biogenicity of Archaean spheroidal microfossils (ca. 3.0 Ga) from the Mount Goldsworthy–Mount Grant area in the northeastern Pilbara Craton, Western Australia". Precambrian Research. 173 (1–4): 50–59. Bibcode:2009PreR..173...50S. doi:10.1016/j.precamres.2009.02.004.

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