Cambrian Stage 2

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
o
p
r
o
t
e
r
o
z
o
i
c

P
a
l
e
o
z
o
i
c

Ediacaran

C
a
m
b
r
i
a
n

Ordovician

T
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r
r
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v
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a
n

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.

Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian series. It lies on top of the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia. Both the upper and lower boundary have not been clearly defined yet by the International Commission on Stratigraphy. Proposals for the lower boundary are the appearance of Small Shelly Fossils, an archaeocyathid species or the mollusc Watsonella crosbyi around ~529 million years ago. The proposed upper boundary might be the first appearance of trilobites around ~521 million years ago.

Possible candidates for a GSSP include the first appearance of Watsonella crosbyi in the Zhujiaqing Formation in Yunnan, China or the Pestrotsvet Formation near the Aldan River on the Siberian Platform.