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 convent ...
s in the
Late Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wher ...
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
The Frasnian is one of two faunal stages in the ...
Stage and followed by the
Famennian
The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used ...
Stage.
Major reef-building was under way during the Frasnian Stage, particularly in western
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...
and
Australia
Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
. On land, the first
forest
A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...
s were taking shape. In
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
, the Antler orogeny peaked, which were contemporary with the Bretonic phase of the
Variscan orogeny
The Variscan 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 ''Variscan'', comes f ...
in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
.
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
Description
Stratigraphy
The West Falls Group is a geologic group in New York. It preserves fossils dating back to the Devonian period.
The West Falls formation is bounded above by the Java Formation and below by the Sonyea Formation. It comp ...
*
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 the ...
*
Genesee Group
The Genesee Group is a geologic formation in Pennsylvania. It preserves fossils dating back to the Devonian period.
It includes submembers:
* West River Shale
* Genundewa Limestone
* Penn Yan Formation
* Geneseo Shale
The Burket Shale is t ...
Name and definition
The Frasnian Stage was proposed in 1879 by French geologist