The Furongian is the fourth and final

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

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

. It lasted from to million years ago. It succeeds the Miaolingian series of the Cambrian and precedes the Lower Ordovician Tremadocian Stage. It is subdivided into three stages: the Paibian,

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 the unnamed 10th stage of the Cambrian.

History and naming

The Furongian was also known as the Cambrian Series 4, and the name replaced the older term Upper Cambrian and equivalent to the local term Hunanian. The present name was ratified 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 2003. () means ' lotus' in Mandarin and refers to

Hunan Hunan is an inland Provinces of China, province in Central China. Located in the middle reaches of the Yangtze watershed, it borders the Administrative divisions of China, province-level divisions of Hubei to the north, Jiangxi to the east, Gu ...

which is known as the "lotus state".

Definition

The lower boundary is defined in the same way as 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. ...

of the Paibian Stage. Both begin with 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 the

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 ...

'' Glyptagnostus reticulatus'' around million years ago. The upper boundary is the lower boundary and GSSP of the Tremadocian Stage which is the first 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 ...

'' around million years ago.

Subdivisions

The following table shows the subdivisions of the Furongian series/epoch:

Biostratigraphy

The base of two of three stages of the Furongian are defined as the first appearance of a trilobite. The base of the Paibian is the first appearance of '' Glyptagnostus reticulatus'' and the base of the

is the first appearance of ''

Agnostotes orientalis ''Agnostotes orientalis'' is a species of agnostid trilobite belonging to the genus '' Agnostotes''. It existed during the Jiangshanian Age ( million years ago) of the Cambrian. It is an important index fossil in biostratigraphy. Description '' ...

''. The still unnamed

Cambrian Stage 10 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. The proposed lower boundary is the first appearance of the trilobite '' Lotagno ...

might be defined as the first appearance of ''

Lotagnostus americanus ''Lotagnostus'' is a genus of very small trilobites in the order Agnostida, which lived on the outer continental shelf, continental shelves worldwide, during the late Upper Cambrian. It was described by Whitehouse in 1936, and the type species is ...

'' or the

'' Eoconodontus notchpeakensis''. The Furongian can be divided into a number of trilobite zones:

Major events

At the beginning of the Furongian epoch, the

Guzhangian The Guzhangian is an uppermost stage of the Miaolingian Series of the Cambrian. It follows the Drumian Stage and precedes the Paibian Stage of the Furongian Series. The base is defined as the first appearance of the trilobite '' Lejopyge laevi ...

– Paibian extinction ended. Species diversity, which had decreased by 45%, returned to its previous level at the very beginning of the

age. The ensuing Jiangshanian extinction reduced species diversity by 55.2% and was followed by an interval of relatively small fluctuations in species richness, which ended shortly after the beginning of the

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

. Steptoean positive carbon isotope excursion (SPICE) occurred in close proximity in time to the Miaolingian–Furongian boundary (and, accordingly, the Guzhangian–Paibian boundary). This event is recorded on almost all Cambrian paleocontinents, but its exact causes are not fully understood. It is assumed that it may be associated with the Sauk megasequence, which in turn is associated with sea level changes; decrease in oxygen or occurrence of euxinic conditions in ocean waters; or the trilobite biomere turnover. From the Furongian to the Early Ordovician, around 495-470 Ma, the

mantle plume A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic ho ...

activity, known as the Ollo de Sapo magmatic event, occurred on the North-Western territory of the

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

which is now the

Iberian Peninsula The Iberian Peninsula ( ), also known as Iberia, is a peninsula in south-western Europe. Mostly separated from the rest of the European landmass by the Pyrenees, it includes the territories of peninsular Spain and Continental Portugal, comprisin ...

Paleontology

Researchers have been noted that the significant macroscopic soft-bodied animals that lived between the Cambrian Explosion and the Great Ordovician Biodiversification Event were not discovered. In 2019, this time interval was named the Furongian Biodiversity Gap by Harper ''et al''. This gap has been characterized as probably caused by lack of rocks, environmental events or a specific palaeogeography and extreme climates of the late Cambrian. However, a review of the literature and locations with Cambrian deposits showed that the gap is caused by the insufficient presence of Furongian deposits in sufficiently studied areas, as well as the lack of attention to

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s of this interregnum. Later discoveries of the Furongian deposits in South China have allowed for a better understanding of the biostratigraphy and fluctuations in species diversity of this epoch. 8502 specimens of

- agnostoid fauna have been collected from the Furongian strata of the Alum Shale Formation of

Bornholm Bornholm () is a List of islands of Denmark, Danish island in the Baltic Sea, to the east of the rest of Denmark, south of Sweden, northeast of Germany and north of Poland. Strategically located, Bornholm has been fought over for centuries. I ...

Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...

. Described gerena include '' Ctenopyge'', '' Eurycare'', '' Leptoplastus'', ''

Olenus In Greek mythology and Roman mythology, Olenus (; Ancient Greek: Ὤλενος ''Olenos'') was the name of several individuals: *Olenus, son of Vulcan and father of Helice and Aex, two nurses of infant Jove. A city in Aulis was named for him. ...

'', '' Parabolina'', '' Peltura'', '' Protopeltura'', '' Sphaerophthalmus'', '' Lotagnostus'' and '' Triangulopyge''.

Benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

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 ...

, including genera '' Rhabdopleura'', '' Dendrograptus'', '' Callograptus'' and '' Siberiograptus'', were found in the Furongian sediments of South China.

References

External links

* * * {{Geological history, p, p, state=collapsed *04 Geological epochs