Frasnian

Frasnian
382.31 ± 1.36 – 372.15 ± 0.46 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Paleogeography of the Late Devonian, 380 Ma
Chronology
−420 — – −415 — – −410 — – −405 — – −400 — – −395 — – −390 — – −385 — – −380 — – −375 — – −370 — – −365 — – −360 — – Paleozoic Devonian C M Early Mid Late E Lochkovian Pragian Emsian Eifelian Givetian Frasnian Famennian Tournaisian S Přídolí     ← Hangenberg event, Famennian glaciation ← Kellwasser event (Late Devonian mass extinction)[1] ← Widespread shrubs & trees[2] ← Hunsrück fauna ← Rhynie chert[3] Subdivision of the Devonian according to the ICS, as of 2024[4] Vertical 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 conodont Ancyrodella rotundiloba
Lower boundary GSSP	Col du Puech de la Suque, Montagne Noire, France 43°30′12″N 3°05′12″E / 43.5032°N 3.0868°E / 43.5032; 3.0868
Lower GSSP ratified	1986[5]
Upper boundary definition	FAD of the conodont Palmatolepis triangularis LAD of the conodonts Ancyrodella and Ozarkodina and the goniatites Gephuroceratidae and Beloceratidae
Upper boundary GSSP	Coumiac quarry, Montagne Noire, France 43°27′41″N 3°02′25″E / 43.4613°N 3.0403°E / 43.4613; 3.0403
Upper GSSP ratified	1993[6]

The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from 382.31 million years ago to 372.15 million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage.

Major reef-building was under way during the Frasnian Stage, particularly in western Canada and Australia. On land, the first forests were taking shape. In North America, the Antler orogeny peaked, which were contemporary with the Bretonic phase of the Variscan orogeny in Europe.

The Frasnian coincides with the second half of the "charcoal gap" in the fossil record, a time when atmospheric oxygen levels were below 13 percent, the minimum necessary to sustain wildfires.^[7]

North American subdivisions of the Frasnian include

• West Falls Group
• Sonyea Group
• Genesee Group

Name and definition

The Frasnian Stage was proposed in 1879 by French geologist Jules Gosselet and was accepted for the lower stage of the Upper Devonian by the Subcommission on Devonian Stratigraphy in 1981.^[8] It is named after the village of Frasnes-lez-Couvin, in the district of Couvin, in Belgium.^[9]

References

1. Kaufmann, Bernd; Trapp, Endres; Mezger, Klaus (July 2004). "The numerical age of the Upper Frasnian (Upper Devonian) Kellwasser horizons: A new U-Pb zircon date from Steinbruch Schmidt (Kellerwald, Germany)" (PDF). The Journal of Geology. 112 (4): 495–501. Bibcode:2004JG....112..495K. doi:10.1086/42107. eISSN 1537-5269. ISSN 0022-1376. JSTOR 421077. LCCN 25013118. OCLC 1608377. S2CID 129963970. Archived from the original (PDF) on February 10, 2024. Retrieved December 16, 2025.
2. Algeo, Thomas; Scheckler, Stephen E. (January 29, 1998). "Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events". Philosophical Transactions of the Royal Society B: Biological Sciences. 353 (1365): 113–130. doi:10.1098/rstb.1998.0195. eISSN 1471-2970. PMC 1692181. S2CID 84656565.
3. Parry, Stephen F.; Noble, Stephen R.; Crowley, Quentin C.; Wellman, Charles H. (June 15, 2011). "A high-precision U–Pb age constraint on the Rhynie Chert Konservat-Lagerstätte: time scale and other implications" (PDF). Journal of the Geological Society. 168 (4). Geological Society of London: 863–872. Bibcode:2011JGSoc.168..863P. doi:10.1144/0016-76492010-043. eISSN 2041-479X. ISSN 0016-7649. LCCN 79641612. OCLC 1934542. S2CID 128679831. Archived (PDF) from the original on July 11, 2025. Retrieved December 16, 2025.
4. "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. December 2024. Retrieved October 23, 2025.
5. Klapper, Gilbert; Feist, Raimund; House, Michael (June 1987). "Decision on the Boundary Stratotype for the Middle/Upper Devonian Series Boundary". Episodes. 10 (2): 97–101. doi:10.18814/epiiugs/1987/v10i2/004. Retrieved 19 December 2020.
6. Klapper, G.; Feist, R.; Becker, R.; House, M. (December 1993). "Definition of the Frasnian/Famennian Stage boundary". Episodes. 16 (4): 433–441. Retrieved 19 December 2020.
7. McGhee, George R. Jr. (12 November 2013). When the Invasion of Land Failed: The Legacy of the Devonian Extinctions. Columbia University Press. pp. 110–11. ISBN 978-0-231-16057-5. Retrieved 21 April 2015.
8. Coen-Aubert, Marie; Boulvain, Frédéric (2006). "Frasnian". Geologica Belgica. 9 (1–2): 19–25. Retrieved 10 March 2013.^{[permanent dead link]}
9. "Frasnian mudmounds from Belgium". University of Liège. Archived from the original on 2011-07-06. Retrieved 2011-02-25.

43°30′12″N 3°05′12″E / 43.5032°N 3.0868°E / 43.5032; 3.0868