Earth:Furongian

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The Furongian or Late Cambrian is the fourth and final epoch and series of the Cambrian. It lasted from 497 to 485.4 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 and the unnamed 10th stage of the Cambrian.[1]

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".[2]

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.[3] 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.[4]

Subdivisions

The following table shows the subdivisions of the Furongian series/epoch:[1]

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 Glyptagnostus reticulatus and the base of the Jiangshanian is the first appearance of Agnostotes orientalis.[2][5] The still unnamed Cambrian Stage 10 might be defined as the first appearance of Lotagnostus americanus or the conodont Eoconodontus notchpeakensis.[6]

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[6] Lotagnostus americanus (undecided)
Jiangshanian Ellipsocephaloides zone, Saukia zone (lower part)[6] Agnostotes orientalis
Paibian ? (?) Glyptagnostus reticulatus
Aphelaspis Zone[7]

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.[8]

Steptoean positive carbon isotope excursion (SPICE) occurred in close proximity in time to the Miaolingian–Furongian boundary (and, accordingly, the Guzhangian–Paibian boundary).[9] 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.[9]

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.[10]

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.[11] 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.[12] 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.[8]

8502 specimens of trilobite-agnostoid fauna have been collected from the Furongian strata of the Alum Shale Formation of Bornholm, Denmark. Described gerena include Ctenopyge, Eurycare, Leptoplastus, Olenus, Parabolina, Peltura, Protopeltura, Sphaerophthalmus, Lotagnostus and Triangulopyge.[13] Benthic graptolites, including genera Rhabdopleura, Dendrograptus, Callograptus and Siberiograptus, were found in the Furongian sediments of South China.[14]

References

  1. ↑ 1.0 1.1 "GSSP Table - Paleozoic Era". https://engineering.purdue.edu/Stratigraphy/gssp/index.php?parentid=77. 
  2. ↑ 2.0 2.1 Cite error: Invalid <ref> tag; no text was provided for refs named Sanchi2004
  3. ↑ "GSSP for the Paibian". https://timescalefoundation.org/gssp/detail.php?periodid=146&top_parentid=77. 
  4. ↑ "GSSP for the Cambrian - Ordovician Boundary". https://engineering.purdue.edu/Stratigraphy/gssp/camord.htm. 
  5. ↑ "GSSP for Jiangshanian". https://timescalefoundation.org/gssp/detail.php?periodid=145&top_parentid=0. 
  6. ↑ 6.0 6.1 6.2 Landing, E.; Westrop, S.R.; Adrain, J.M. (19 September 2011). "The Lawsonian Stage - the Eoconodontus notchpeakensis FAD and HERB carbon isotope excursion define a globally correlatable terminal Cambrian stage". Bulletin of Geosciences: 621–640. doi:10.3140/bull.geosci.1251. http://www.geology.cz/bulletin/fulltext/1251_Landing.pdf. 
  7. ↑ 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. https://csuepress.columbusstate.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1032&context=bibliography_faculty. 
  8. ↑ 8.0 8.1 Yiying Deng, Junxuan Fan, Shengchao Yang, Yukun Shi, Zhengbo Lu, Huiqing Xu, Zongyuan Sun, Fangqi Zhao, Zhangshuai Hou (2023). "No Furongian Biodiversity Gap: Evidence from South China". Palaeogeography, Palaeoclimatology, Palaeoecology 618 (1). doi:10.1016/j.palaeo.2023.111492. Bibcode: 2023PPP...61811492D. https://www.researchgate.net/publication/369096101. 
  9. ↑ 9.0 9.1 Guangying Ren, Mikaela A. Pulsipher, James D. Schiffbauer, Jin-Liang Yuan, Ying Guo, Chao Chang, Fanwei Meng, Yan Zhao, Jian Gao (2021). "A contiguous record of the SPICE event, sea-level change and the first appearance of Fenghuangella laevis in Shandong Province, North China". Lethaia 54 (5): 1—12. doi:10.1111/let.12425. Bibcode: 2021Letha..54..631R. https://www.researchgate.net/publication/351483592. 
  10. ↑ Josep Maria Casas, J. Brendan Murphy, Teresa Sanchez-Garcia, Jacques de Poulpiquet, José-Javier Alvaro, A. Díez-Montes, Joan Guimerà (2023). "Does the Ollo de Sapo magmatic event support Furongian-Tremadocian mantle plume activity fringing NW Gondwana?". International Geology Review 66 (10): 1956–1970. doi:10.1080/00206814.2023.2263787. https://www.researchgate.net/publication/374674894. 
  11. ↑ 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). https://www.researchgate.net/publication/305585918. 
  12. ↑ David A.T. Harper, Borja Cascales-Miñana, Yuan-Dong Zhang, Timothy Topper, Thomas Servais, Per Ahlberg (2019). "The Furongian (late Cambrian) Biodiversity Gap: Real or apparent". Palaeoworld 28 (1–2): 4—12. doi:10.1016/j.palwor.2019.01.007. https://www.researchgate.net/publication/331061567. 
  13. ↑ Arne Thorshøj Nielsen, Line Frigaard Andersen (2021). "Furongian (upper Cambrian) trilobites and agnostoids from the Alum Shale Formation of Bornholm, Denmark: revised taxonomy and biostratigraphy". Bulletin of the Geological Society of Denmark 69: 123–213. doi:10.37570/bgsd-2021-69-08. ISSN 2245-7070. https://2dgf.dk/xpdf/bull69-123-213.pdf. 
  14. ↑ Jörg Maletz, Xuejian Zhu, Yuan-Dong Zhang (2022). "Graptolithina from the Guole Biota (Furongian, upper Cambrian) of South China". Palaeoworld 31 (8): 582—590. doi:10.1016/j.palwor.2022.03.002. https://www.researchgate.net/publication/359266658. 

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