faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by conven ...
s in the
Late Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding ...
Period. It lasted from million years ago to million years ago. It was preceded by the
Givetian
The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian Stage. It is named after the town of Givet in ...
Stage and followed by the
Famennian
The Famennian is the later of two faunal stages in the Late Devonian epoch. The most recent estimate for its duration is that it lasted from around 371.1 to 359.3 million years ago. An earlier 2012 estimate, still used by the International Commis ...
Stage.
Major reef-building was under way during the Frasnian Stage, particularly in western
Canada
Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
and
Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
. On land, the first
forest
A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...
s were taking shape. In
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, the Antler orogeny peaked, which were contemporary with the Bretonic phase of the
Variscan orogeny
The Variscan orogeny, or Hercynian orogeny, was a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica (Laurussia) and Gondwana to form the supercontinent of Pangaea.
Nomenclature
The name ''Varis ...
in
Europe
Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
.
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
*
West Falls Group
The West Falls Group is a geologic group in the Appalachian Basin. It dates back to the Devonian period. Also stratigraphically equivalent to the Portage Group. Description Stratigraphy
The West Falls Group is a geologic group in New York. It d ...
*
Sonyea Group
The Sonyea Group is a geologic group in the northern part of the Appalachian Basin. It preserves fossils dating back to the Devonian period.
In the western part, it is divided into the Cashaqua Shale at the top, and the Middlesex Shale at th ...
*
Genesee Group
The Genesee Formation (Group) is a geologic formation in New York. It is equivalent the Harrell Shale in Pennsylvania. It dates back to the Upper Devonian period. It is the basal unit of the Frasnian and Upper Devonian period. The Genesee Forma ...
Name and definition
The Frasnian Stage was proposed in 1879 by French geologist
Jules Gosselet
Jules-Auguste Gosselet (19 April 1832 – 20 March 1916) was a French geologist born in Cambrai, France.Frasnes-lez-Couvin, in the district of
Couvin
Couvin (; ) is a municipality and city of Wallonia located in the province of Namur, Belgium.
On 1 January 2018 the municipality had 13,782 inhabitants. Couvin is the second largest municipality of Belgium by surface area, after Tournai. The tot ...