Cambrian Stage 3

Key events in the Cambrian

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-550 —

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-540 —

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-530 —

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-520 —

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-510 —

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-500 —

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-490 —

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N
e
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p
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t
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o
z
o
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P
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Ediacaran

C
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b
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Ordovician

T
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v
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S
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2

S
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3

F
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Fortunian

"Stage 2"

"Stage 3"

"Stage 4"

"Stage 5"

Drumian

Guzhangian

Paibian

Jiangshanian

"Stage 10"

 

 

 

 

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Baykonur
glaciation

Baykonur
glaciation

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←

Orsten Fauna

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Burgess Shale

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Kaili biota

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Archaeocyatha extinction

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Emu Bay Shale

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Sirius Passet biota

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Chengjiang biota

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First Trilobites

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SSF diversification, first brachiopods & archaeocyatha

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First halkieriids, mollusсs, hyoliths SSF

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Treptichnus pedum trace
Large negative peak δ 13C_carb excursion

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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 or top have been formally defined yet. The lower boundary is loosely defined as the first appearance of trilobites which happened around ~521 million years ago. 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.

Naming

The International Commission on Stratigraphy has not officially named the 3rd stage of the Cambrian. Sometimes this stage is referred to as "Atdabanian" which is used by geologists working in Siberia.

Biostratigraphy

The oldest trilobites known is Lemdadella which appears at the beginning of the Fallotaspis zone.