Cambrian Stage 3
| Cambrian Stage 3 | ||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chronology | ||||||||||||||||||||||||||||||||||||||
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| Etymology | ||||||||||||||||||||||||||||||||||||||
| Name formality | Informal | |||||||||||||||||||||||||||||||||||||
| Usage information | ||||||||||||||||||||||||||||||||||||||
| Celestial body | Earth | |||||||||||||||||||||||||||||||||||||
| Regional usage | Global (ICS) | |||||||||||||||||||||||||||||||||||||
| Time scale(s) used | ICS Time Scale | |||||||||||||||||||||||||||||||||||||
| Definition | ||||||||||||||||||||||||||||||||||||||
| Chronological unit | Age | |||||||||||||||||||||||||||||||||||||
| Stratigraphic unit | Stage | |||||||||||||||||||||||||||||||||||||
| Time span formality | Formal | |||||||||||||||||||||||||||||||||||||
| Lower boundary definition | Not formally defined | |||||||||||||||||||||||||||||||||||||
| Lower boundary definition candidates | FAD of Trilobites | |||||||||||||||||||||||||||||||||||||
| Lower boundary GSSP candidate section(s) | None | |||||||||||||||||||||||||||||||||||||
| Upper boundary definition | Not formally defined | |||||||||||||||||||||||||||||||||||||
| Upper boundary definition candidates | FAD of the Trilobites Olenellus or Redlichia | |||||||||||||||||||||||||||||||||||||
| Upper boundary GSSP candidate section(s) | None | |||||||||||||||||||||||||||||||||||||
Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approximately to the first appearance of trilobites, about 521 million years ago,[2] though the globally asynchronous appearance of trilobites warrants the use of a separate, globally synchronous marker to define the base.[3] The upper boundary and beginning of Cambrian Stage 4 is informally defined as the first appearance of the trilobite genera Olenellus or Redlichia around 514 million years ago.[4]
Naming
[edit]The International Commission on Stratigraphy has not officially named the 3rd stage of the Cambrian. The stage approximately corresponds to the "Atdabanian", which is used by geologists working in Siberia.[5]
Biostratigraphy
[edit]The oldest trilobite known is Lemdadella which appears at the beginning of the Fallotaspis zone.[6] The Cambrian radiation of animal phyla ends here, after the diversification and origination of arthropods, molluscs, lophophorates, chordates (including vertebrates) among others.[7]
References
[edit]- Zhang (2017). "Challenges in defining the base of Cambrian Series 2 and Stage 3". Earth-Science Reviews. 172: 124–139. Bibcode:2017ESRv..172..124Z. doi:10.1016/j.earscirev.2017.07.017.
- ^ "Chart/Time Scale". stratigraphy.org. International Commission on Stratigraphy.
- ^ Ahlberg, Per; Babcock, Loren E. "Subcommission on Cambrian Stratigraphy Annual Report 2017" (PDF). International Commission on Stratigraphy. Archived (PDF) from the original on 2023-07-16. Retrieved 2024-03-27.
- ^ "ISCS Working Groups: Working Group on the Stage 3 GSSP". International Subcommission on Cambrian Stratigraphy. Archived from the original on 2023-09-26.
- ^ "GSSP Table - Paleozoic Era". Geologic Timescale Foundation. Archived from the original on 2023-10-08. Retrieved 2024-03-27.
- ^ "The 13th International Field Conference of the Cambrian Stage Subdivision Working Group" (PDF). Episodes. 31 (4): 440–441. Archived from the original (PDF) on 2014-11-05. Retrieved 2024-03-27.
- ^ Yuan, J.L.; Zhu, X.J.; Lin, J.P.; Zhu, M.Y. (22 September 2011). "Tentative correlation of Cambrian Series 2 between South China and other continents" (PDF). Bulletin of Geosciences: 397–404. doi:10.3140/bull.geosci.1274. Archived from the original (PDF) on 2024-01-18. Retrieved 2024-03-27.
- ^ Degan Shu, Yukio Isozaki, Xingliang Zhang, Jan Han, Shigenori Maruyama (2014). "Birth and early evolution of metazoans". Gondwana Research. 25 (3): 884—895. Bibcode:2014GondR..25..884S. doi:10.1016/j.gr.2013.09.001.
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External links
[edit]- "GSSP Table - Paleozoic Era". Geologic Timescale Foundation. Archived from the original on 2023-10-08. Retrieved 2024-06-13.
- "GSSPs - The Cambrian System 2019". International Commission on Stratigraphy. Archived from the original on 2023-07-21.
