Cambrian Stage 3

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]

Key events in the Cambrian

-540 —

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-535 —

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-530 —

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-525 —

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-520 —

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-515 —

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-510 —

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-505 —

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-500 —

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-495 —

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-490 —

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-485 —

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N
P
Z

P
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e
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z
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Ediacaran

C
a
m
b
r
i
a
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Ordovician

T
e
r
r
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v
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S
e
r
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2

M
i
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F
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Fortunian

"Stage 2"

"Stage 3"

"Stage 4"

←

Orsten Fauna

←

Burgess Shale

←

Kaili biota

←

Archaeocyatha extinction

←

Emu Bay Shale

←

Sirius Passet biota

←

Chengjiang biota

←

First Trilobites

←

SSF diversification, first brachiopods & archaeocyatha

←

First halkieriids, mollusсs, hyoliths SSF

←

Treptichnus pedum trace
Large negative peak δ 13C_carb excursion

←

Baykonurian glaciation

Major Glacial period

Stratigraphic scale of the ICS subdivisions and Precambrian/Cambrian boundary.

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]

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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.

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[1] ttp://www.palaeontology.geo.uu.se/ISCS/ISCS%20Annual%20Report%202017.pdf

[2] ttp://www.palaeontology.geo.uu.se/ISCS/ISCS_working_groups.html

[GSSP_Table_-_Paleozoic_Era-3] "GSSP Table - Paleozoic Era". Retrieved 18 November 2012.

[13th_conference-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.

[Yuan_2011-5] 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.