The Wuliuan

stage Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...

is the fifth stage 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 Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

, and the first stage of the

Miaolingian The Miaolingian is the third Series of the Cambrian Period, and was formally named in 2018. It lasted from about to million years ago and is divided in ascending order into 3 stages: the Wuliuan, Drumian, and Guzhangian. The Miaolingian is prec ...

Series of the Cambrian. It was formally defined by the

International Commission on Stratigraphy The International Commission on Stratigraphy (ICS), sometimes unofficially referred to as the International Stratigraphic Commission, is a daughter or major subcommittee grade scientific organization that concerns itself with stratigraphy, strati ...

in 2018. Its base is defined by the first appearance of the trilobite species ''

Oryctocephalus indicus ''Oryctocephalus indicus'' is a species of corynexochid trilobite from the Cambrian. Its first appearance is proposed for the lower boundary of the Wuliuan, which corresponds to the beginning of the Miaolingian (The other proposal was ''Ovatoryc ...

''; it ends with the beginning of the

Drumian The Drumian is a stage of the Miaolingian Series of the Cambrian. It succeeds the Wuliuan and precedes the Guzhangian. The base is defined as the first appearance of the trilobite '' Ptychagnostus atavus'' around million years ago. The top is de ...

Stage, marked by the first appearance of the trilobite ''

Ptychagnostus atavus ''Ptychagnostus atavus'' is a species of agnostid trilobite. It was originally described by Swedish paleontologist Sven Axel Tullberg as ''Agnostus atavus'' in 1880. It is used in biostratigraphy as an index fossil. Its first appearance at the ...

'' around million years ago. The '

golden spike The golden spike (also known as the last spike) is the ceremonial 17.6-Carat (purity), karat gold final Rail spike, spike driven by Leland Stanford to join the rails of the first transcontinental railroad across the United States connecting t ...

' that formally defines the base of the age is driven into the Wuliu-Zengjiayan (乌溜-曾家崖) section of the

Kaili formation The Kaili Formation () is a Formation (stratigraphy), stratigraphic formation which was deposited during the Lower and Middle Cambrian (~513 to 506 million years ago). The formation is approximately thick and was named after the city Kaili City, ...

, near Balang Village in the Miaoling Mountains, Guizhou, China.

GSSP

Three sections were discussed as

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. ...

candidates: the Wuliu-Zengjiayan section near Balang in

Guizhou ) , image_skyline = , image_caption = , image_map = Guizhou in China (+all claims hatched).svg , mapsize = 275px , map_alt = Map showing the location of Guizhou Province , map_caption = Map s ...

province (China), a section on Split Mountain in

Nevada Nevada ( ; ) is a landlocked state in the Western United States. It borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the seventh-most extensive, th ...

(USA) and the "Molodo river section" along the

Molodo river The Molodo (, , ''Muolada'') is a river in Bulunsky District, Sakha Republic, Russia. It is a major left tributary of the Lena (river), Lena. The Molodo is long, and the area of its basin . The banks of the Molodo are not inhabited. River sedime ...

(Sakha Republic, Russia). The Wuliu-Zengjiayan section is an outcrop of the

Kaili Formation The Kaili Formation () is a Formation (stratigraphy), stratigraphic formation which was deposited during the Lower and Middle Cambrian (~513 to 506 million years ago). The formation is approximately thick and was named after the city Kaili City, ...

in the Wuliu quarry. The first candidate for the beginning of the Wuliuan was the trilobite ''

'', the second candidate was the trilobite ''

Ovatoryctocara granulata ''Ovatoryctocara granulata'' is a species of corynexochid trilobite from the Cambrian. Its first appearance is one of the proposals for the base of Wuliuan The Wuliuan stage is the fifth stage of the Cambrian, and the first stage of the Miaoli ...

''. The Wuliu-Zengjiayan section was chosen as the formal base in 2018, with the first appearance of ''Oryctocephalus indicus'' being chosen as the defining marker for the GSSP.

Major events

The base of Wuliuan stage (and, accordingly, the entire Miaolingian Series) is characterized by the first major extinction of trilobites, known as the

Olenellid Biomere boundary Olenellidae is an extinct family of redlichiid trilobite arthropods. Olenellids lived during the late Lower Cambrian (Botomian/Toyonian) in the ''Olenellus''-zone in the former paleocontinent of Laurentia and parts of what became the Famatini ...

. This event is linked by a sudden negative carbonate carbon excursion.

Paleontology

Benthic

graptolites Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian (Miaolingian, Wuliuan) through th ...

have reached a considerable diversity im the Wuliuan. The most common graptolite genus of this age is '' Sphenoecium'', whose robust colonies were found all over the world. Numerous

panarthropods Panarthropoda is a clade comprising the greatest diversity of animal groups. It contains the extant phyla Arthropoda (Euarthropoda), Tardigrada (water bears) and Onychophora (velvet worms), although the precise relationships among these remained ...

, including

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 ...

s, agnostoids, hurdiids and bradoriids, are known from Wuliuan deposits.

References

External links

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