| Cambrian Stage 3 | |
|---|---|
| ~521 – ~514 Ma | |
| Chronology | |
Key events in the Cambrian -540 — – -535 — – -530 — – -525 — – -520 — – -515 — – -510 — – -505 — – -500 — – -495 — – -490 — – -485 — – Major Glacial period Stratigraphic scale of the ICS subdivisions and Precambrian/Cambrian boundary. | |
| 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,[1] though the globally asynchronous appearance of trilobites warrants the use of a separate, globally synchronous marker to define the base.[2] 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.[3]
Naming
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.[4]
Biostratigraphy
The oldest trilobite known is Lemdadella which appears at the beginning of the Fallotaspis zone.[5]
References
- Zhang (2017). "Challenges in defining the base of Cambrian Series 2 and Stage 3". Earth-Science Reviews. 172: 124–139. doi:10.1016/j.earscirev.2017.07.017.
- ^ http://www.palaeontology.geo.uu.se/ISCS/ISCS%20Annual%20Report%202017.pdf
- ^ http://www.palaeontology.geo.uu.se/ISCS/ISCS_working_groups.html
- ^ "GSSP Table - Paleozoic Era". Retrieved 18 November 2012.
- ^ "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 2012-11-18.
- ^ 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. Retrieved 23 November 2012.