Floian

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,{{cite journal|last=Bergström|first=Stig M.|author2=Anita Löfgren |author3=Jörg Maletz |title=The GSSP of the Second (Upper) Stage of the Lower Ordovician Series: Diabasbrottet at Hunneberg, Province of Västergötland, Southwestern Sweden|journal=Episodes|year=2004|volume=27|issue=4|pages=265–272|url=https://timescalefoundation.org/references/Floian.pdf|access-date=2024-04-20|archive-url=https://web.archive.org/web/20240416190519/https://timescalefoundation.org/references/Floian.pdf|archive-date=2024-04-16|url-status=live}} but the ICS adapted Floian as the official name of the stage.{{cite journal|author=Stig M. Bergström, Stanley Finney, Chen Xu, Daniel Goldman, Stephen A. Leslie|year=2006|url=https://www.idunn.no/doi/pdf/10.1080/00241160600847439|title=Three new Ordovician global stage names|journal=Lethaia|volume=39|issue=4|page=287–288|doi=10.1080/00241160600847439|archive-url=https://web.archive.org/web/20240420120752/https://www.idunn.no/doi/pdf/10.1080/00241160600847439|archive-date=2024-04-20|url-status=live|url-access=subscription}}

The GSSP of the Floian is the lower Tøyen Shale in Diabasbrottet Quarry ({{Coord|58.3589|N|12.5024|E|display=inline}}) 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. Radiometric dating has set the Tremadocian-Floian boundary at {{Period start|Floian}} million years ago.

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.{{cite web|url=https://timescalefoundation.org/gssp/detail.php?periodid=138&top_parentid=77|title=GSSP for Dapingian Stage

|publisher=Geologic TimeScale Foundation|archive-url=https://web.archive.org/web/20240404224051/https://timescalefoundation.org/gssp/detail.php?periodid=138&top_parentid=77|archive-date=2024-04-04|url-status=live}}

Partial analogues of Floian stage in Baltoscandia are Hunneberg stage (lower) and Billingen stage (upper).{{cite journal|author=Helje Pärnaste, Viive Viira|year=2012|url=https://www.researchgate.net/publication/258439672|title=On the lower boundary of the Floian Stage in Estonia|journal=Estonian Journal of Earth Sciences|volume=61|issue=2|page=205–209|doi=10.3176/earth.2012.4.02|doi-access=free}}{{cite web|url=https://paleobiodb.org/classic/displayTimescale?scale=180|title=Ordovician of the Baltic|website=Paleobiology Database|access-date=2024-04-20|archive-url=https://web.archive.org/web/20240416113415/https://paleobiodb.org/classic/displayTimescale?scale=180|archive-date=2024-04-16|url-status=live}} On the Siberian Platform, Ugorian stage corresponds to Floian.{{cite book|author=V. E. Pavlov, Andrei Dronov, Alexander Larionov, Tatiana Yu. Tolmacheva|year=2022|url=https://www.researchgate.net/publication/358137383|title=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]|publisher=Springer Nature|page=107–114|isbn=978-3-030-91467-7|doi=10.1007/978-3-030-91467-7|issn=2524-3438}}

The global Billingen Transgressive Event occurred in the Early Floian age. Black graptolitic argillites of Gorny Altai as well as conglomerates and gritstones of Salair, Russia, possibly correlates with this event.{{cite journal|author=N. V. Sennikov, O. T. Obut, E. V. Lykova, A. V. Timokhin, R. A. Khabibulina, T. A. Shcherbanenko|year=2021|url=https://www.gt-crust.ru/jour/article/view/1209/550|title=Event Stratigraphy and Correlation Problems of the Ordovician strata of Gorny Altai and Salair|journal=Geodynamics & Tectonophysics|volume=12|issue=2|page=246—260|doi=10.5800/GT-2021-12-2-0523|language=ru|doi-access=free}}

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.{{cite journal|author=Dong-Jin Lee, Robert Elias, Brian R. Pratt|year=2022|url=https://www.researchgate.net/publication/358188752|title=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=Journal of Paleontology|volume=96|issue=3|page=1—14|doi=10.1017/jpa.2021.122}}

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.{{cite journal|author=Yong Yi Zhen, Ian G. Percival, Yuan-Dong Zhang|year=2014|url=https://www.researchgate.net/publication/268526802|title=Floian (Early Ordovician) conodont-based biostratigraphy and biogeography of the Australasian Superprovince|journal=Palaeoworld|volume=24|issue=1-1|page=100–109|doi=10.1016/j.palwor.2014.10.011}}

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.{{cite journal|author=Jörg Maletz|year=2022|title=Roland Skoglund’s late Floian graptolites from Dalarna, central Sweden|journal=Historical Biology|volume=35|issue=9|page=1583-1604|doi=10.1080/08912963.2022.2104642}}

Trilobites of the genera Tsaidamaspis, Zhiyia and Liexiaspis were found in the Floian part of the Duoquanshan Formation, northwest China.{{cite journal|author=Xin Wei, Zhiqiang Zhou|year=2023|url=https://www.researchgate.net/publication/376577519|title=Floian, Early Ordovician trilobites from the Olongbluk Terrane, northwest China|journal=Acta Palaeontologica Polonica|volume=68|issue=|page=|doi=10.4202/app.01102.2023|doi-access=free}}

Falloaster anquiroisitus, an asterozoan of problematic classification, is known from the Floian Garden City Formation of Idaho, USA.{{cite journal|author=Daniel B. Blake, Forest J. Gahn, Thomas E. Guensburg|year=2019|url=|title=An Early Ordovician (Floian) asterozoan (Echinodermata) of problematic class-level affinities|journal=Journal of Paleontology|volume=94|issue=2|page=1-8|doi=10.1017/jpa.2019.82}}

{{Reflist}}

• {{cite web|url=https://timescalefoundation.org/gssp/image.php?periodid=140&top_parentid=77&imageid=382|title=GSSP for base of the Floian Stage in the Diabasbrottet section, Mt Hunneberg, Sweden, with stratigraphic ranges of graptolites and conodonts|website=timescalefoundation.org|language=en|archive-url=https://web.archive.org/web/20240404223917/https://timescalefoundation.org/gssp/image.php?periodid=140&top_parentid=77&imageid=382|archive-date=2024-04-04|url-status=live}}
• {{cite web|title=GSSP Table - Paleozoic Era|url=https://timescalefoundation.org/gssp/index.php?parentid=77|website=timescalefoundation.org|language=en|archive-url=https://web.archive.org/web/20231008002417/https://timescalefoundation.org/gssp/index.php?parentid=77|archive-date=2023-10-08|url-status=live}}
• {{cite web|url=https://ordovician.stratigraphy.org/floian|title=Floian|publisher=Subcommission on Ordovician Stratigraphy|language=en|archive-url=https://web.archive.org/web/20210618075152/https://ordovician.stratigraphy.org/floian|archive-date=2021-06-18|url-status=live}}

{{Clear}}

{{Geological history|p|p|state=collapsed}}

.

Category:Ordovician geochronology