Furongian

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Furongian
~497 – 485.4 ± 1.9 Ma
Chronology
←
←
Dresbachian extinction
Upper GSSP ratified2000[4]

The Furongian is the fourth and final

Lower Ordovician Tremadocian Stage. It is subdivided into three stages: the Paibian, Jiangshanian and the unnamed 10th stage of the Cambrian.[5]

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 in 2003. Fúróng (芙蓉) means 'lotus' in Mandarin and refers to Hunan which is known as the "lotus state".[3]

Definition

The lower boundary is defined in the same way as the

GSSP of the Paibian Stage. Both begin with the first appearance of the trilobite Glyptagnostus reticulatus around 497 million years ago.[6] The upper boundary is the lower boundary and GSSP of the Tremadocian Stage which is the first appearance of the conodont Iapetognathus fluctivagus around 485.4 million years ago.[7]

Subdivisions

The following table shows the subdivisions of the Furongian series/epoch:[5]

Series Stage Age (
Ma
)
Lower Ordovician
Floian 477.7
Tremadocian 485.4
Furongian
Stage 10 489.5
Jiangshanian 494
Paibian 497
Miaolingian
Guzhangian 500.5
Drumian 504.5
Wuliuan 509

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

Eoconodontus notchpeakensis.[9]

The Furongian can be divided into a number of trilobite zones:

Series Stage Trilobite zone Trilobite GSSP
Furongian Stage 10 Saukia zone (upper part), Eurekia apopsis zone, Tangshanaspis Zone, Parakoldinioidia zone, Symphysurina zone[9] Lotagnostus americanus (undecided)
Jiangshanian Ellipsocephaloides zone, Saukia zone (lower part)[9] Agnostotes orientalis
Paibian ? (?) Glyptagnostus reticulatus
Aphelaspis Zone[10]

Major events

At the beginning of the Furongian epoch, the Guzhangian–Paibian extinction ended. Species diversity, which had decreased by 45%, returned to its previous level at the very beginning of the Jiangshanian 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.[11]

Steptoean positive carbon isotope excursion (SPICE) occurred in close proximity in time to the Miaolingian–Furongian boundary (and, accordingly, the Guzhangian–Paibian boundary).[12] 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.[12]

From the Furongian to the Early Ordovician, around 495-470 Ma, the mantle plume activity, known as the Ollo de Sapo magmatic event, occurred on the North-Western territory of the Gondwana which is now the Iberian Peninsula.[13]

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.[14] 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 fossils of this interregnum.[15] 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.[11]

8502 specimens of

graptolites, including genera Rhabdopleura, Dendrograptus, Callograptus and Siberiograptus, were found in the Furongian sediments of South China.[17]

References

  1. ^ "Chart/Time Scale". stratigraphy.org. International Commission on Stratigraphy.
  2. ^ Shanchi, Peng; Babcock, Loren; Robinson, Richard; Huanling, Lin; Rees, Margaret; Saltzman, Matthew. "PROPOSED GLOBAL STANDARD STRATOTYPE-SECTION AND POINT FOR THE PAIBIAN STAGE AND FURONGIAN SERIES (UPPER CAMBRIAN)" (PDF). International Subcomission on Cambrian Stratigraphy. Archived (PDF) from the original on 2015-07-25. Retrieved 2024-04-14.
  3. ^
    doi:10.1080/00241160410002081. Archived
    (PDF) from the original on 2017-10-08. Retrieved 2024-04-14.
  4. doi:10.18814/epiiugs/2001/v24i1/005. Archived
    (PDF) from the original on 2024-03-25. Retrieved 2024-04-14.
  5. ^ a b "GSSP Table - Paleozoic Era". Archived from the original on 2023-10-08.
  6. ^ "GSSP for the Paibian". Archived from the original on 2022-05-26. Retrieved 2024-04-14.
  7. ^ "GSSP for the Cambrian - Ordovician Boundary". Archived from the original on 2016-03-03. Retrieved 2024-04-14.
  8. ^ "GSSP for Jiangshanian". Archived from the original on 2023-01-24. Retrieved 2024-04-14.
  9. ^
    doi:10.3140/bull.geosci.1251. Archived from the original
    (PDF) on 2023-08-29.
  10. ^ David R. Schwimmer, William M. Montante. "An Aphelaspis zone (Upper Cambrian, paibian) trilobite faunule in the central conasauga River Valley, North Georgia, USA". Southeastern Geology. 49 (1): 31–41. Archived from the original on 2023-05-07.
  11. ^
    doi:10.1016/j.palaeo.2023.111492.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  12. ^
    doi:10.1111/let.12425.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  13. doi:10.1080/00206814.2023.2263787.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  14. ^ Rudy Lerosey-Aubril, Stacey Gibb, John Paterson, Brian D. E. Chatterton (2016). "Late Cambrian (Furongian) exceptional fossils from McKay Group of British Columbia, Canada". Conference: Palaeontology Down Under 2. Adelaide, Australia.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  15. doi:10.1016/j.palwor.2019.01.007.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  16. ISSN 2245-7070. Archived
    (PDF) from the original on 2023-10-26.
  17. doi:10.1016/j.palwor.2022.03.002.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )


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