Floian
ColorFloian
Time start477.1
Time start uncertainty1.2
Time end471.3
Time end uncertainty1.4
TimelineOrdovician
Name formalityFormal
Celestial bodyearth
UsageGlobal (ICS)
Timescales usedICS Time Scale
Chrono unitAge
Strat unitStage
Timespan formalityFormal
Lower boundary defFAD of the Graptolite Tetragraptus approximatus
Lower gssp locationDiabasbrottet quarry, Västergötland, Sweden
Lower gssp coords58.3589°N 12.5024°E
Lower gssp accept date2002[1]
Upper boundary defFAD of the Conodont Baltoniodus triangularis
Upper gssp locationHuanghuachang section, Huanghuachang, Yichang, China
Upper gssp coords30.8605°N 110.3740°E
Upper gssp accept date2007[2]

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.[3] The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.[4]

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,[5] but the ICS adapted Floian as the official name of the stage.[6]

GSSP

The GSSP of the Floian is the lower Tøyen Shale in Diabasbrottet Quarry (58.3589°N 12.5024°E) 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.[5] Radiometric dating has set the Tremadocian-Floian boundary at million years ago.[3]

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.[7]

Regional stages

Partial analogues of Floian stage in Baltoscandia are Hunneberg stage (lower) and Billingen stage (upper).[8][9] On the Siberian Platform, Ugorian stage corresponds to Floian.[10]

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.[11]

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.[12]

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.[13]

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.[14]

Trilobites of the genera Tsaidamaspis, Zhiyia and Liexiaspis were found in the Floian part of the Duoquanshan Formation, northwest China.[15]

Falloaster anquiroisitus, an asterozoan of problematic classification, is known from the Floian Garden City Formation of Idaho, USA.[16]

References

  1. ^ 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.
  2. ^ 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". Lethaia. 42: 218-231. doi:10.1111/j.1502-3931.2008.00148.x. Archived 2024-01-06 at the Wayback Machine. Retrieved 2024-04-20.
  3. ^ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. Retrieved 2024-06-13.
  4. ^ "GSSP for Floian Stage". Geologic TimeScale Foundation. Archived 2024-04-16 at the Wayback Machine.
  5. ^ 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". Episodes. 27 (4): 265–272. Archived 2024-04-16 at the Wayback Machine. Retrieved 2024-04-20.
  6. ^ 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 2024-04-20 at the Wayback Machine.
  7. ^ "GSSP for Dapingian Stage". Geologic TimeScale Foundation. Archived 2024-04-04 at the Wayback Machine.
  8. ^ 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
  9. ^ "Ordovician of the Baltic". Paleobiology Database. Archived 2024-04-16 at the Wayback Machine. Retrieved 2024-04-20.
  10. ^ 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
  11. ^ 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" (in Russian). Geodynamics & Tectonophysics. 12 (2): 246—260. doi:10.5800/GT-2021-12-2-0523
  12. ^ 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
  13. ^ 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
  14. ^ 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
  15. ^ 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
  16. ^ 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