Floian

Floian
	477.7 ± 1.4 – 470.0 ± 1.4 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Chronology
	Epochs in the Ordovician -485 — – -480 — – -475 — – -470 — – -465 — – -460 — – -455 — – -450 — – -445 — – P ; a ; l ; e ; o ; z ; o ; i ; c Ꞓ O; r; d; o; v; i; c; i; a; n S F E; a; r; l; y M; i; d; d; l; e L; a; t; e L Stage 10 Tremadocian Floian Dapingian Darriwilian Sandbian Katian Hirnantian Rhuddanian ← First land plant spores[1] ← Ordovician meteor event[2][3] Epochs of the Ordovician Period. ; Axis scale: millions of years ago.;
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
Time span formality	Formal
Lower boundary definition	FAD of the Graptolite Tetragraptus approximatus
Lower boundary GSSP	Diabasbrottet quarry, Västergötland, Sweden; 58.3589°N 12.5024°E
GSSP ratified	2002[4]
Upper boundary definition	FAD of the Conodont Baltoniodus triangularis
Upper boundary GSSP	Huanghuachang section, Huanghuachang, Yichang, China; 30.8605°N 111.3740°E
GSSP ratified	2007[5]

The Floian is the second stage of the Ordovician geologic 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.[6]

Naming and history

The Floian stage is named after Flo, a village in Västergötland, southern Sweden. The name "Floan" was proposed in 2004, but the International Commission on Stratigraphy adapted Floian as the official name of the stage.[7]

GSSP

The GSSP of the Floian is the Diabasbrottet Quarry (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 above the base of the Tøyen Shale.[7] Radiometric dating has set the Tremadocian-Floian boundary at 477.7million years ago.[6]

Palaeontology

Agnathans

Agnathans of the Floian
Taxa	Presence	Location	Description	Images
Arandaspis	Tremadocian-Floian	Alice Springs, Australia

Cephalopods

Cephalopods of the Tremadocian
Taxa	Presence	Location	Description	Images
Proterovaginoceras	Tremadocian-Darriwilian

References

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.
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.
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
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.
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. Retrieved 13 December 2020.
"GSSP Table - Paleozoic Era". Geologic TimeScale Foundation. Retrieved 24 November 2012.
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. Retrieved 20 September 2012.

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[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] 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.

[5] 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. Retrieved 13 December 2020.

[GSSP_Table_-_Paleozoic_Era-6] "GSSP Table - Paleozoic Era". Geologic TimeScale Foundation. Retrieved 24 November 2012.

[Bergström_2004-7] 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. Retrieved 20 September 2012.