Ediacaran-Cambrian boundary plate tectonics.png
A map of the world as it appeared during the mid-Ediacaran. (600 ma)
Name formalityFormal
Name ratified1990
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Chronological unitPeriod
Stratigraphic unitSystem
Time span formalityFormal
Lower boundary definition
  • Worldwide distinct cap carbonates.
  • Beginning of a distinctive pattern of secular changes in carbon isotopes.
Lower boundary GSSPEnorama Creek section, Flinders Ranges, South Australia
31°19′53″S 138°38′00″E / 31.3314°S 138.6334°E / -31.3314; 138.6334
Lower GSSP ratifiedMarch 2004[1]
Upper boundary definitionAppearance of the Ichnofossil Treptichnus pedum
Upper boundary GSSPFortune Head section, Newfoundland, Canada
47°04′34″N 55°49′52″W / 47.0762°N 55.8310°W / 47.0762; -55.8310
Upper GSSP ratified1992[2]
Atmospheric and climatic data
Mean atmospheric O2 contentc. 8 vol %
(40 % of modern)
Mean atmospheric CO2 contentc. 4500 ppm
(16 times pre-industrial)
Mean surface temperaturec. 17 °C
(3 °C above modern)

The Ediacaran Period ( /ˌdiˈækərən, ˌɛdi-/ EE-dee-AK-ər-ən, ED-ee-)[3] is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya.[4] It marks the end of the Proterozoic Eon, and the beginning of the Phanerozoic Eon. It is named after the Ediacara Hills of South Australia.

The Ediacaran Period's status as an official geological period was ratified in 2004 by the International Union of Geological Sciences (IUGS), making it the first new geological period declared in 120 years.[5][6][7] Although the period takes its name from the Ediacara Hills where geologist Reg Sprigg first discovered fossils of the eponymous Ediacaran biota in 1946,[8] the type section is located in the bed of the Enorama Creek[9] within Brachina Gorge[10] in the Flinders Ranges of South Australia, at 31°19′53.8″S 138°38′0.1″E / 31.331611°S 138.633361°E / -31.331611; 138.633361.

The Ediacaran marks the first appearance of widespread multicellular fauna following the end of Snowball Earth glaciation events, the so-called Ediacaran biota, which is represented by now-extinct relatively simple animal phyla such as Proarticulata (bilaterians with articulation including Dickinsonia and Spriggina), Petalonamae (sea pen-like animals including Charnia), Disc-shaped forms (radial-shaped animals including Cyclomedusa) and Trilobozoa (animals with tri-radial symmetry including Tribrachidium). Most of those organisms appeared during or after the Avalon explosion event 575 million years ago and died out during an End-Ediacaran extinction event 539 million years ago. Some modern groups of animals also appeared during this period, including cnidarians and early bilaterians such as Xenacoelomorpha. Mollusc-like Kimberella also lived during the Ediacaran. Fossilized organisms with shells or skeletons were yet to evolve in the Cambrian, the superseding period of the Phanerozoic eon.

The supercontinent Pannotia formed and broke apart by the end of the period. The Ediacaran also witnessed several glaciation events, such as the Gaskiers and Baykonurian glaciations. The Shuram excursion also occurred during this period, but its glacial origin is unlikely.

  1. ^ Knoll, Andrew H.; Walter, Malcolm R.; Narbonne, Guy M.; Christie-Black, Nicholas (3 March 2006). "The Ediacaran Period: a new addition to the geologic time scale" (PDF). Lethaia. 39: 13–30. doi:10.1080/00241160500409223. Retrieved 6 December 2020.
  2. ^ Brasier, Martin; Cowie, John; Taylor, Michael. "Decision on the Precambrian-Cambrian boundary stratotype" (PDF). Episodes. 17. Retrieved 6 December 2020.
  3. ^ "Ediacaran". Dictionary.com Unabridged (Online). n.d.
  4. ^ "Stratigraphic Chart 2022" (PDF). International Stratigraphic Commission. February 2022. Retrieved 20 April 2022.
  5. ^ Cite error: The named reference Knoll2004a was invoked but never defined (see the help page).
  6. ^ Knoll, A. H.; Walter, MR; Narbonne, G. M; Christie-Blick, N (30 July 2004). "A new period for the geologic time scale" (PDF). Science. 305 (5684): 621–622. doi:10.1126/science.1098803. PMID 15286353. S2CID 32763298.
  7. ^ Knoll, A. H.; Walter, M. R.; Narbonne, G. M. & Christie-Blick, N. (March 2006). "The Ediacaran Period: A new addition to the geologic time scale" (PDF). Lethaia. 39: 13–30. doi:10.1080/00241160500409223. Archived from the original (PDF) on 21 February 2007.
  8. ^ Sprigg, Reg. C. (1947). "Early Cambrian (?) jellyfishes from the Flinders Ranges, South Australia". Transactions of the Royal Society of South Australia. 71 (2): 212–224.
  9. ^ "Geological time gets a new period: Geologists have added a new period to their official calendar of Earth's history—the first in 120 years". London: BBC. 17 May 2004. Accessed 27 December 2010.
  10. ^ South Australian Museum Newsletter April 2005 Archived 17 February 2011 at the Wayback Machine Accessed 9 August 2010.

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