Wikipedia

Floian

The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from 477.7 to 470 million years ago. The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.[7]

Floian
477.7 ± 1.4 – 470.0 ± 1.4 Ma
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Lower boundary definitionFAD of the Graptolite Tetragraptus approximatus
Lower boundary GSSPDiabasbrottet quarry, Västergötland, Sweden
58°21′32″N 12°30′09″E / 58.3589°N 12.5024°E / 58.3589; 12.5024
Lower GSSP ratified2002[5]
Upper boundary definitionFAD of the Conodont Baltoniodus triangularis
Upper boundary GSSPHuanghuachang section, Huanghuachang, Yichang, China
30°51′38″N 111°22′26″E / 30.8605°N 111.3740°E / 30.8605; 111.3740
Upper GSSP ratified2007[6]

History and naming edit

The base of this stage was ratified by the International Commission on Stratigraphy (ICS) in 2002. The Floian Stage is named after Flo, a village in Västergötland, southern Sweden. The name "Floan" was proposed in 2004,[8] but the ICS adapted Floian as the official name of the stage.[9]

GSSP edit

The GSSP of the Floian is the lower Tøyen Shale in Diabasbrottet Quarry (58°21′32″N 12°30′09″E / 58.3589°N 12.5024°E / 58.3589; 12.5024) which is an outcrop of a shale-dominated stratigraphic succession. The lower boundary of the Floian is defined as the first appearance of Tetragraptus approximatus which is about 2.1 above the Cambrian strata.[8] Radiometric dating has set the Tremadocian-Floian boundary at 477.7 million years ago.[10]

The upper boundary which is also the base of the Dapingian stage is defined as the first appearance of the conodont species Baltoniodus triangularis at the GSSP in the Huanghuachang Section, Hubei Province, China.[11]

Regional stages edit

Partial analogues of Floian stage in Baltoscandia are Hunneberg stage (older) and Billingen stage (younger).[12][13] On the Siberian Platform, Ugorian stage corresponds to Floian.[14]

Paleontology edit

Discovered in the Floian strata of Newfoundland, coral-like fossils of Reptamsassia divergens and Reptamsassia minuta are the oldest example of symbiotic intergrowth of modular species. This allows to judge the level of development of reef ecosystems of the Early Ordovician.[15]

Conodonts Serratognathus, Prioniodus and Oepikodus were distributed in Kazakhstan, Korea, China, Indochina and Australasia during the Floian age. Two species of Paroistodus are known from the Floian deposits of Baltoscandia and South China.[16]

Several thousand chemically isolated graptolite specimens including genera Baltograptus and Pseudophyllograptus were collected from the upper Floian sediments of Skattungbyn, Dalarna, central Sweden. Presented mostly by juveniles and isolated siculae, these graptolites inhabited primarily in shallow water environment.[17]

Trilobites of the genera Tsaidamaspis, Zhiyia and Liexiaspis were found in the Floian part of the Duoquanshan Formation, northwest China.[18]

Falloaster anquiroisitus, an asterozoan of problematic classification, is known from the Floian Garden City Formation of Idaho, USA.[19]

References edit

  1. ^ Wellman, C.H.; Gray, J. (2000). "The microfossil record of early land plants". Phil. Trans. R. Soc. B. 355 (1398): 717–732. doi:10.1098/rstb.2000.0612. PMC 1692785. PMID 10905606.
  2. ^ Korochantseva, Ekaterina; Trieloff, Mario; Lorenz, Cyrill; Buykin, Alexey; Ivanova, Marina; Schwarz, Winfried; Hopp, Jens; Jessberger, Elmar (2007). "L-chondrite asteroid breakup tied to Ordovician meteorite shower by multiple isochron 40 Ar- 39 Ar dating". Meteoritics & Planetary Science. 42 (1): 113–130. Bibcode:2007M&PS...42..113K. doi:10.1111/j.1945-5100.2007.tb00221.x.
  3. ^ Lindskog, A.; Costa, M. M.; Rasmussen, C.M.Ø.; Connelly, J. N.; Eriksson, M. E. (2017-01-24). "Refined Ordovician timescale reveals no link between asteroid breakup and biodiversification". Nature Communications. 8: 14066. doi:10.1038/ncomms14066. ISSN 2041-1723. PMC 5286199. PMID 28117834. It has been suggested that the Middle Ordovician meteorite bombardment played a crucial role in the Great Ordovician Biodiversification Event, but this study shows that the two phenomena were unrelated
  4. ^ "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
  5. ^ Bergström, M.; Löfgren, Anita; Maletz, Jörg (December 2004). "The GSSP of the Second (Upper) Stage of the Lower Ordovician Series: Diabasbrottet at Hunneberg, Province of Västergötland, Southwestern Sweden". Episodes. 27 (4): 265–272. Retrieved 13 December 2020.
  6. ^ Chen, Xu; Bergström, Stig; Zhang, Yuan-Dong; Fan, Jun-Xuan (2009). "The base of the Middle Ordovician in China with special reference to the succession at Hengtang near Jiangshan, Zhejiang Province, southern China" (PDF). Lethaia. 42: 218–231. doi:10.1111/j.1502-3931.2008.00148.x. Archived (PDF) from the original on 2024-01-06. Retrieved 2024-04-20.
  7. ^ "GSSP for Floian Stage". Geologic TimeScale Foundation. Archived from the original on 2024-04-16.
  8. ^ a b Bergström, Stig M.; Anita Löfgren; Jörg Maletz (2004). "The GSSP of the Second (Upper) Stage of the Lower Ordovician Series: Diabasbrottet at Hunneberg, Province of Västergötland, Southwestern Sweden" (PDF). Episodes. 27 (4): 265–272. Archived (PDF) from the original on 2024-04-16. Retrieved 2024-04-20.
  9. ^ Stig M. Bergström, Stanley Finney, Chen Xu, Daniel Goldman, Stephen A. Leslie (2006). "Three new Ordovician global stage names". Lethaia. 39 (4): 287–288. doi:10.1080/00241160600847439. Archived from the original on 2024-04-20.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. Retrieved 2024-04-20.
  11. ^ "GSSP for Dapingian Stage". Geologic TimeScale Foundation. Archived from the original on 2024-04-04.
  12. ^ Helje Pärnaste, Viive Viira (2012). "On the lower boundary of the Floian Stage in Estonia". Estonian Journal of Earth Sciences. 61 (2): 205–209. doi:10.3176/earth.2012.4.02.
  13. ^ "Ordovician of the Baltic". Paleobiology Database. Archived from the original on 2024-04-16. Retrieved 2024-04-20.
  14. ^ V. E. Pavlov, Andrei Dronov, Alexander Larionov, Tatiana Yu. Tolmacheva (2022). Magnetostratigraphic Constraints on the Position of the Tremadocian–Floian Boundary at the Key Section of the Moyero River Valley (Siberian Platform) [In book: Problems of Geocosmos–2020]. Springer Nature. p. 107–114. doi:10.1007/978-3-030-91467-7. ISBN 978-3-030-91467-7. ISSN 2524-3438.{{cite book}}: CS1 maint: multiple names: authors list (link)
  15. ^ Dong-Jin Lee, Robert Elias, Brian R. Pratt (2022). "Reptamsassia n. gen. (Amsassiaceae n. fam.; calcareous algae) from the Lower Ordovician (Floian) of western Newfoundland, and the earliest symbiotic intergrowth of modular species". Journal of Paleontology. 96 (3): 1—14. doi:10.1017/jpa.2021.122.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  16. ^ Yong Yi Zhen, Ian G. Percival, Yuan-Dong Zhang (2014). "Floian (Early Ordovician) conodont-based biostratigraphy and biogeography of the Australasian Superprovince". Palaeoworld. 24 (1–1): 100–109. doi:10.1016/j.palwor.2014.10.011.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ^ Jörg Maletz (2022). "Roland Skoglund's late Floian graptolites from Dalarna, central Sweden". Historical Biology. 35 (9): 1583-1604. doi:10.1080/08912963.2022.2104642.
  18. ^ Xin Wei, Zhiqiang Zhou (2023). "Floian, Early Ordovician trilobites from the Olongbluk Terrane, northwest China". Acta Palaeontologica Polonica. 68. doi:10.4202/app.01102.2023.
  19. ^ Daniel B. Blake, Forest J. Gahn, Thomas E. Guensburg (2019). "An Early Ordovician (Floian) asterozoan (Echinodermata) of problematic class-level affinities". Journal of Paleontology. 94 (2): 1-8. doi:10.1017/jpa.2019.82.{{cite journal}}: CS1 maint: multiple names: authors list (link)

External links edit

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