Floian

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title: "Floian" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["floian", "early-ordovician", "ordovician-geochronology"] description: "Second and last age of the Early Ordovician epoch" topic_path: "general/floian" source: "https://en.wikipedia.org/wiki/Floian" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Second and last age of the Early Ordovician epoch ::

::data[format=table title="Infobox geologic timespan"]

Field	Value
name	Floian
color	Floian
time_start	477.1
time_start_uncertainty	1.2
time_end	471.3
time_end_uncertainty	1.4
timeline	Ordovician
name_formality	Formal
celestial_body	earth
usage	Global (ICS)
timescales_used	ICS Time Scale
chrono_unit	Age
strat_unit	Stage
timespan_formality	Formal
lower_boundary_def	FAD of the Graptolite Tetragraptus approximatus
lower_gssp_location	Diabasbrottet quarry, Västergötland, Sweden
lower_gssp_coords
lower_gssp_accept_date	2002
upper_boundary_def	FAD of the Conodont Baltoniodus triangularis
upper_gssp_location	Huanghuachang section, Huanghuachang, Yichang, China
upper_gssp_coords
upper_gssp_accept_date	2007
::

| name = Floian | color = Floian | time_start = 477.1 | time_start_uncertainty = 1.2 | time_end = 471.3 | time_end_uncertainty = 1.4 | image_map = | caption_map = | image_outcrop = | caption_outcrop = | image_art = | caption_art = | timeline = Ordovician | former_subdivisions = | formerly_part_of = | partially_contained_in = | partially_contains = | name_formality = Formal | name_accept_date = | alternate_spellings = | synonym1 = | synonym1_coined = | synonym2 = | synonym2_coined = | synonym3 = | synonym3_coined = | nicknames = | former_names = | proposed_names = | celestial_body = earth | usage = Global (ICS) | timescales_used = ICS Time Scale | formerly_used_by = | not_used_by = | chrono_unit = Age | strat_unit = Stage | proposed_by = | timespan_formality = Formal | lower_boundary_def = FAD of the Graptolite Tetragraptus approximatus | lower_gssp_location = Diabasbrottet quarry, Västergötland, Sweden | lower_gssp_coords = | lower_gssp_accept_date = 2002 | upper_boundary_def = FAD of the Conodont Baltoniodus triangularis | upper_gssp_location = Huanghuachang section, Huanghuachang, Yichang, China | upper_gssp_coords = | upper_gssp_accept_date = 2007 | o2 = | co2 = | temp = | sea_level = The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician series. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.

History and naming

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, but the ICS adapted Floian as the official name of the stage.

GSSP

The GSSP of the Floian is the lower Tøyen Shale in Diabasbrottet Quarry () 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 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}}

Regional stages

Partial analogues of Floian stage in Baltoscandia are Hunneberg stage (lower) and Billingen stage (upper). On the Siberian Platform, Ugorian stage corresponds to Floian.

Major events

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.

Paleontology

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.

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.

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.

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

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

References

References

1. (December 2004). "The GSSP of the Second (Upper) Stage of the Lower Ordovician Series: Diabasbrottet at Hunneberg, Province of Västergötland, Southwestern Sweden". Episodes.
2. (2009). "The base of the Middle Ordovician in China with special reference to the succession at Hengtang near Jiangshan, Zhejiang Province, southern China". Lethaia.
3. "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy.
4. "GSSP for Floian Stage". Geologic TimeScale Foundation.
5. Bergström, Stig M.. (2004). "The GSSP of the Second (Upper) Stage of the Lower Ordovician Series: Diabasbrottet at Hunneberg, Province of Västergötland, Southwestern Sweden". Episodes.
6. Stig M. Bergström, Stanley Finney, Chen Xu, Daniel Goldman, Stephen A. Leslie. (2006). "Three new Ordovician global stage names". [[Lethaia]].
7. Helje Pärnaste, Viive Viira. (2012). "On the lower boundary of the Floian Stage in Estonia". Estonian Journal of Earth Sciences.
8. "Ordovician of the Baltic".
9. 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]].
10. N. V. Sennikov, O. T. Obut, E. V. Lykova, A. V. Timokhin, R. A. Khabibulina, T. A. Shcherbanenko. (2021). "Event Stratigraphy and Correlation Problems of the Ordovician strata of Gorny Altai and Salair". Geodynamics & Tectonophysics.
11. 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.
12. Yong Yi Zhen, Ian G. Percival, Yuan-Dong Zhang. (2014). "Floian (Early Ordovician) conodont-based biostratigraphy and biogeography of the Australasian Superprovince". Palaeoworld.
13. Jörg Maletz. (2022). "Roland Skoglund’s late Floian graptolites from Dalarna, central Sweden". Historical Biology.
14. Xin Wei, Zhiqiang Zhou. (2023). "Floian, Early Ordovician trilobites from the Olongbluk Terrane, northwest China". Acta Palaeontologica Polonica.
15. Daniel B. Blake, Forest J. Gahn, Thomas E. Guensburg. (2019). "An Early Ordovician (Floian) asterozoan (Echinodermata) of problematic class-level affinities". Journal of Paleontology.

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