A map of the world as it appeared during the Late Carboniferous. (300 Ma)
2 content over period duration
(162 % of modern level)
2 content over period duration
(3 times pre-industrial level)
(0 °C above modern level)
Based on a study of the British rock succession, it was the first of the modern 'system' names to be employed, and reflects the fact that many coal beds were formed globally during that time.[4] The Carboniferous is often treated in North America as two geological periods, the earlier Mississippian and the later Pennsylvanian.[5] Terrestrial animal life was well established by the Carboniferous period.[6] Amphibians were the dominant land vertebrates, of which one branch would eventually evolve into amniotes, the first solely terrestrial vertebrates.
Arthropods were also very common, and many (such as Meganeura) were much larger than those of today. Vast swaths of forest covered the land, which would eventually be laid down and become the coal beds characteristic of the Carboniferous stratigraphy evident today. Also during this period, the atmospheric content of oxygen reached its highest levels in geological history, 35%[7] compared with 21% today, allowing terrestrial invertebrates to evolve to great size.[7]
The later half of the period experienced glaciations, low sea level, and mountain building as the continents collided to form Pangaea. A minor marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred at the end of the period, caused by climate change.[8]
Subdivisions
In the United States the Carboniferous is usually broken into Mississippian (earlier) and Pennsylvanian (later) subperiods. The Mississippian is about twice as long as the Pennsylvanian, but due to the large thickness of coal-bearing deposits with Pennsylvanian ages in Europe and North America, the two subperiods were long thought to have been more or less equal in duration.[9]
In Europe the Lower Carboniferous sub-system is known as the Dinantian, comprising the Tournaisian and Visean Series, dated at 362.5-332.9 Ma, and the Upper Carboniferous sub-system is known as the Silesian, comprising the Namurian, Westphalian, and Stephanian Series, dated at 332.9-298.9 Ma. The Silesian is roughly contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, and the Westphalian as the Coal Measures and Pennant Sandstone.
The International Commission on Stratigraphy (ICS) faunal stages (in bold) from youngest to oldest, together with some of their regional subdivisions, are: