Cambrian Stage 10

From Infogalactic: the planetary knowledge core
Jump to: navigation, search
Key events in the Cambrian
view • discuss • edit
-550 —
-540 —
-530 —
-520 —
-510 —
-500 —
-490 —
"Stage 10"
 
 
 
 
* * * * * * * * * * * *
* * * * * * * * * * * * * * * * * * * * * * * * *
Baykonur
glaciation
Baykonur
glaciation
* * * * * * * * * * * *
* * * * * * * * * * * * * * * * * * * * * * * * *
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.

Stage 10 of the Cambrian is the still unnamed third and final stage of the Furongian Series. It follows the Jiangshanian and precedes the Ordovician Tremadocian Stage.[1] The proposed lower boundary is the first appearance of the trilobite Lotagnostus americanus around ~489.5 million years ago, but other fossils are also being discussed (see below). The upper boundary is defined as the appearance of the conodont Iapetognathus fluctivagus which marks the beginning of the Tremadocian and is radiometrically dated as 485.4 ± 1.9 million years ago.[2]

Naming

The 10th stage of the Cambrian has not been formally named by the ICS yet, although a number of local names exist.[1] Several authors favor the name "Lawsonian" after Lawson Cove, in the Wah Wah Mountains of Utah.[3][4]

Stratotype

The ICS is still discussing which geological section and biostratigraphic marker will be used to define the base of the 10th Cambrian stage.

Likely candidates for the section are still investigated. A first proposal was a section near Duibian, Zhejiang province (China). Newer publications favor Steamboat Pass in the House Range of Utah. If a conodont is used for the base the stage then many more sections would be likely candidates for the GSSP, e.g. in Australia, Kazakhstan and Canada.[3]

Candidates for the biostratigraphic marker are the first appearance of a trilobite or conodont species. The trilobite Lotagnostus americanus was first suggested by the ICS, but has proven to be problematic.[2][3] In 2006 another working group proposed the first appearance of Cordylodus andresi.[5] Currently the first appearance of Eoconodontus notchpeakensis is favored by many authors because it is globally widespread and is independent of facies (known from continental rise to peritidal environments).[3]

The Eoconodontus notchpeakensis proposal would also incorporate a non-biostratigraphic marker to correlate the beginning of Stage 10 globally. A carbon isotope excursion (the HERB-event) occurs in the lower part of the E. notchpeakensis range.[3]

Subdivisions

Cambrian Stage 10 can be subdivided using different biostratigraphic zones. Several conodont zone and subzones can be distinguished. The same is true for trilobites.[3]

References

  1. 1.0 1.1 Lua error in package.lua at line 80: module 'strict' not found.
  2. 2.0 2.1 Lua error in package.lua at line 80: module 'strict' not found.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 Lua error in package.lua at line 80: module 'strict' not found.
  4. Lua error in package.lua at line 80: module 'strict' not found.
  5. Lua error in package.lua at line 80: module 'strict' not found.


Paleozoic Era
Cambrian Ordovician Silurian Devonian Carboniferous Permian