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Cambrian

For other uses, see Cambrian (disambiguation). Not to be confused with Cambria or Cumbria.
"Cambrian fauna" redirects here. For the first evolutionary fauna, see Evolutionary fauna § Cambrian fauna.

Cambrian
Earth in the middle of the Cambrian Period, c. 510 Ma[citation needed]
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitPeriod
Stratigraphic unitSystem
First proposed byAdam Sedgwick, 1835
Time span formalityFormal
Lower boundary definitionAppearance of the Ichnofossil Treptichnus pedum
Lower boundary GSSPFortune Head section, Newfoundland, Canada
47°04′34″N 55°49′52″W / 47.0762°N 55.8310°W / 47.0762; -55.8310
Lower GSSP ratified1992[2]
Upper boundary definitionFAD of the Conodont Iapetognathus fluctivagus.
Upper boundary GSSPGreenpoint section, Green Point, Newfoundland, Canada
49°40′58″N 57°57′55″W / 49.6829°N 57.9653°W / 49.6829; -57.9653
Upper GSSP ratified2000[3]
Atmospheric and climatic data
Sea level above present dayRising steadily from 4 m to 90 m[4]

The Cambrian ( /ˈkæmbri.ən, ˈkeɪm-/ KAM-bree-ən, KAYM-) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon.[5] The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovician Period 485.4 Ma.[6]

Most of the continents lay in the southern hemisphere surrounded by the vast Panthalassa Ocean.[7] The assembly of Gondwana during the Ediacaran and early Cambrian led to the development of new convergent plate boundaries and continental-margin arc magmatism along its margins that helped drive up global temperatures.[8] Laurentia lay across the equator, separated from Gondwana by the opening Iapetus Ocean.[7]

The Cambrian was a time of greenhouse climate conditions, with high levels of atmospheric carbon dioxide and low levels of oxygen in the atmosphere and seas. Upwellings of anoxic deep ocean waters into shallow marine environments lead to extinction events, whilst periods of raised oxygenation led to increased biodiversity.[9]

The Cambrian marked a profound change in life on Earth; prior to the Period, the majority of living organisms were small, unicellular and poorly preserved. Complex, multicellular organisms gradually became more common during the Ediacaran, but it was not until the Cambrian that organisms with mineralised shells and skeletons are found in the rock record, and the rapid diversification of lifeforms, known as the Cambrian explosion, produced the first representatives of most modern animal phyla.[10] The Period is also unique in its unusually high proportion of lagerstätte deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells.[11]

By the end of the Cambrian, myriapods,[12][13] arachnids,[14] and hexapods[15] started adapting to the land, along with the first plants.[16][17]

  1. ^ "Chart/Time Scale". stratigraphy.org. International Commission on Stratigraphy.
  2. ^ Brasier, Martin; Cowie, John; Taylor, Michael (March–June 1994). "Decision on the Precambrian-Cambrian boundary stratotype" (PDF). Episodes. 17 (1–2): 3–8. doi:10.18814/epiiugs/1994/v17i1.2/002. Archived (PDF) from the original on 9 October 2022.
  3. ^ Cooper, Roger; Nowlan, Godfrey; Williams, S. H. (March 2001). "Global Stratotype Section and Point for base of the Ordovician System" (PDF). Episodes. 24 (1): 19–28. doi:10.18814/epiiugs/2001/v24i1/005. Archived (PDF) from the original on 9 October 2022. Retrieved 6 December 2020.
  4. ^ Haq, B. U.; Schutter, SR (2008). "A Chronology of Paleozoic Sea-Level Changes". Science. 322 (5898): 64–8. Bibcode:2008Sci...322...64H. doi:10.1126/science.1161648. PMID 18832639. S2CID 206514545.
  5. ^ Howe 1911, p. 86.
  6. ^ "International Stratigraphic Chart" (PDF). International Commission on Stratigraphy. June 2023. Archived (PDF) from the original on 13 July 2023. Retrieved 19 July 2023.
  7. ^ a b Cite error: The named reference :1 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference :10 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference :9 was invoked but never defined (see the help page).
  10. ^ Butterfield, N. J. (2007). "Macroevolution and macroecology through deep time". Palaeontology. 50 (1): 41–55. Bibcode:2007Palgy..50...41B. doi:10.1111/j.1475-4983.2006.00613.x.
  11. ^ Orr, P. J.; Benton, M. J.; Briggs, D. E. G. (2003). "Post-Cambrian closure of the deep-water slope-basin taphonomic window". Geology. 31 (9): 769–772. Bibcode:2003Geo....31..769O. doi:10.1130/G19193.1.
  12. ^ Collette, Gass & Hagadorn 2012.
  13. ^ Edgecombe, Gregory D.; Strullu-Derrien, Christine; Góral, Tomasz; Hetherington, Alexander J.; Thompson, Christine; Koch, Marcus (2020). "Aquatic stem group myriapods close a gap between molecular divergence dates and terrestrial fossil record". Proceedings of the National Academy of Sciences. 117 (16): 8966–8972. Bibcode:2020PNAS..117.8966E. doi:10.1073/pnas.1920733117. PMC 7183169. PMID 32253305. S2CID 215408474.
  14. ^ Lozano-Fernandez, Jesus; Tanner, Alastair R.; Puttick, Mark N.; Vinther, Jakob; Edgecombe, Gregory D.; Pisani, Davide (2020). "A Cambrian–Ordovician Terrestrialization of Arachnids". Frontiers in Genetics. 11: 182. doi:10.3389/fgene.2020.00182. PMC 7078165. PMID 32218802.
  15. ^ Lozano-Fernandez, Jesus; Carton, Robert; Tanner, Alastair R.; Puttick, Mark N.; Blaxter, Mark; Vinther, Jakob; Olesen, Jørgen; Giribet, Gonzalo; Edgecombe, Gregory D.; Pisani, Davide (2016). "A molecular palaeobiological exploration of arthropod terrestrialization". Philosophical Transactions of the Royal Society B: Biological Sciences. 371 (1699). doi:10.1098/rstb.2015.0133. PMC 4920334. PMID 27325830.
  16. ^ De Vries, Jan; De Vries, Sophie; Fürst-Jansen, Janine M R. (2020). "Evo-physio: On stress responses and the earliest land plants". Journal of Experimental Botany. 71 (11): 3254–3269. doi:10.1093/jxb/eraa007. PMC 7289718. PMID 31922568.
  17. ^ Morris, Jennifer L.; Puttick, Mark N.; Clark, James W.; Edwards, Dianne; Kenrick, Paul; Pressel, Silvia; Wellman, Charles H.; Yang, Ziheng; Schneider, Harald; Donoghue, Philip C. J. (2018). "The timescale of early land plant evolution". Proceedings of the National Academy of Sciences. 115 (10): E2274–E2283. Bibcode:2018PNAS..115E2274M. doi:10.1073/pnas.1719588115. PMC 5877938. PMID 29463716.

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