Stage 10 of the Cambrian is the still unnamed third and final stage of the

Furongian The Furongian is the fourth and final epoch and series of the Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding ...

series. It follows the

Jiangshanian The Jiangshanian is the middle stage of the Furongian series. It follows the Paibian Stage and is succeeded by the still unnamed Stage 10 of the Cambrian. The base is defined as the first appearance of the trilobite '' Agnostotes orientalis ...

and precedes the Ordovician Tremadocian Stage. The proposed lower boundary is the first appearance of the trilobite '' Lotagnostus americanus'' around million years ago, but other fossils are also being discussed ( see below). The upper boundary is defined as the appearance of the

conodont Conodonts, are an extinct group of marine jawless vertebrates belonging to the class Conodonta (from Ancient Greek κῶνος (''kōnos''), meaning " cone", and ὀδούς (''odoús''), meaning "tooth"). They are primarily known from their hard ...

Iapetognathus fluctivagus ''Iapetognathus fluctivagus'' is a species of denticulate cordylodan conodonts belonging to the genus '' Iapetognathus''. It existed during the Tremadocian Age ( million years ago) of the Ordovician. It is an important index fossil in biostrat ...

'' which marks the beginning of the Tremadocian and is radiometrically dated as million years ago.

Naming

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

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

. The lower part of the North American Skullrockian Stage corresponds roughly to the Cambrian Stage 10. The name "Nelegerian", after the Neleger River in

Yakutia Sakha, officially the Republic of Sakha (Yakutia), is a republics of Russia, republic of Russia, and the largest federal subject of Russia by area. It is located in the Russian Far East, along the Arctic Ocean, with a population of one million ...

, was also proposed in 2011.

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 ) , translit_lang1_type2 = , translit_lang1_info2 = ( Hangzhounese) ( Ningbonese) (Wenzhounese) , image_skyline = 玉甑峰全貌 - panoramio.jpg , image_caption = View of the Yandang Mountains , image_map = Zhejiang i ...

province (China). Note recent publications favor Steamboat Pass in the House Range of

. If a conodont is used for the base the stage then many more sections would be likely candidates for the

GSSP A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. ...

, e.g. in Australia, Kazakhstan and Canada. Candidates for the biostratigraphic marker are the

first appearance In comic books and other stories with a long history, first appearance refers to the first issue to feature a fictional character. These issues are often highly valued by collectors due to their rarity and iconic status. Reader interest in fir ...

of a

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

or conodont species. The trilobite ''Lotagnostus americanus'' was first suggested by the ICS, but has proven to be problematic. In 2006 another working group proposed the first appearance of '' Cordylodus andresi''. The first appearance of '' Eoconodontus notchpeakensis'' is favored by many authors because it is globally widespread and is independent of

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

(known from continental rise to peritidal environments). 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.

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.

References

External links

* * {{Geological history, p, p, state=collapsed Cambrian geochronology Geological ages Cambrian Utah Furongian