Frasnian

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.

Frasnian
382.7 ± 1.6 – 372.2 ± 1.6 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 S Devonian C M Přídolí Early Mid Late EM Lochkovian Pragian Emsian Eifelian Givetian Frasnian Famennian Tournai.           ← Hangenberg event, Famennian glaciation ← Kellwasser event (Late Devonian mass extinction)[1] ← Widespread[2] shrubs & trees ← Hunsrück fauna ← Rhynie chert[3] Subdivision of the Devonian according to the ICS, as of 2023[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 43.5032°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 43.4613°N 3.0403°E / 43.4613; 3.0403
Upper GSSP ratified	1993[6]

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]