Key events in the Cambrian
-550 —
-540 —
-530 —
-520 —
-510 —
-500 —
-490 —
 
 
 
 
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Orsten Fauna
Archaeocyatha extinction
SSF diversification, first brachiopods & archaeocyatha
Treptichnus pedum trace
Large negative peak δ 13Ccarb excursion
First Cloudina & Namacalathus mineral tubular fossils
Stratigraphic scale of the ICS subdivisions and Precambrian/Cambrian boundary.

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]

NamingEdit

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]

BiostratigraphyEdit

The oldest trilobite known is Lemdadella which appears at the beginning of the Fallotaspis zone.[5]

ReferencesEdit

  • 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.
  1. ^ http://www.palaeontology.geo.uu.se/ISCS/ISCS%20Annual%20Report%202017.pdf
  2. ^ http://www.palaeontology.geo.uu.se/ISCS/ISCS_working_groups.html
  3. ^ "GSSP Table - Paleozoic Era". Retrieved 18 November 2012.
  4. ^ "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.
  5. ^ 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.