Frasnian
The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from 382.7 million years ago to 372.2 million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage.
| Frasnian | |||||||||||||||||
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Paleogeography of the Late Devonian, 380 Ma | |||||||||||||||||
| Chronology | |||||||||||||||||
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| 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 | ||||||||||||||||
| Lower GSSP ratified | 1986 | ||||||||||||||||
| 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 | ||||||||||||||||
| Upper GSSP ratified | 1993 | ||||||||||||||||
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.
North American subdivisions of the Frasnian include
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