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Carboniferous
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The Carboniferous is a geologic period and system that extends from the end of the Devonian period, about 359.2 ± 2.5 Ma (million years ago), to the beginning of the Permian period, about 299.0 ± 0.8 Ma
The Carboniferous was a time of glaciation, low sea level and mountain building; a minor marine extinction event occurred in the middle of the period. The name comes from the Latin word for coal, carbo.
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Encyclopedia
The Carboniferous is a geologic period and system that extends from the end of the Devonian period, about 359.2 ± 2.5 Ma (million years ago), to the beginning of the Permian period, about 299.0 ± 0.8 Ma
The Carboniferous was a time of glaciation, low sea level and mountain building; a minor marine extinction event occurred in the middle of the period. The name comes from the Latin word for coal, carbo. Carboniferous means "coal-bearing". Many beds of coal were laid down all over the world during this period, hence the name.
Subdivisions
In the USA the Carboniferous is usually broken into Mississippian (earlier) and Pennsylvanian (later) Epochs. The Faunal stages from youngest to oldest, together with some of their subdivisions, are:
Late Pennsylvanian: Gzhelian (most recent)
- Noginskian / Virgilian (part)
Late Pennsylvanian: Kasimovian
- Klazminskian
- Dorogomilovksian / Virgilian (part)
- Chamovnicheskian / Cantabrian / Missourian
- Krevyakinskian / Cantabrian / Missourian
Middle Pennsylvanian: Moscovian
- Myachkovskian / Bolsovian / Desmoinesian
- Podolskian / Desmoinesian
- Kashirskian / Atokan
- Vereiskian / Bolsovian / Atokan
Early Pennsylvanian: Bashkirian / Morrowan
- Melekesskian / Duckmantian
- Cheremshanskian / Langsettian
- Yeadonian
- Marsdenian
- Kinderscoutian
Late Mississippian: Serpukhovian
- Alportian
- Chokierian / Chesterian / Elvirian
- Arnsbergian / Elvirian
- Pendleian
Middle Mississippian: Visean
- Brigantian / St Genevieve / Gasperian / Chesterian
- Asbian / Meramecian
- Holkerian / Salem
- Arundian / Warsaw / Meramecian
- Chadian / Keokuk / Osagean (part) / Osage (part)
Early Mississippian: Tournaisian (oldest)
- Ivorian / Osagean (part) / Osage (part)
- Hastarian / Kinderhookian / Chouteau
Paleogeography
A global drop in sea level at the end of the Devonian reversed early in the Carboniferous; this created the widespread epicontinental seas and carbonate deposition of the Mississippian. There was also a drop in south polar temperatures; southern Gondwanaland was glaciated throughout the period, though it is uncertain if the ice sheets were a holdover from the Devonian or not. These conditions apparently had little effect in the deep tropics, where lush coal swamps flourished within 30 degrees of the northernmost glaciers.
A mid-Carboniferous drop in sea-level precipitated a major marine extinction, one that hit crinoids and ammonites especially hard. This sea-level drop and the associated unconformity in North America separate the Mississippian period from the Pennsylvanian period. This happened about 320 million years ago, at the onset of the Permo-Carboniferous Glaciation.
The Carboniferous was a time of active mountain-building, as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America-Europe (Laurussia) along the present line of eastern North America. This continental collision resulted in the Hercynian orogeny in Europe, and the Alleghenian orogeny in North America; it also extended the newly-uplifted Appalachians southwestward as the Ouachita Mountains. In the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China (which would collide in the Latest Carboniferous), and South China continents were still separated from Laurasia. The Late Carboniferous Pangaea was shaped like an "O".
There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, which was inside the "O" in the Carboniferous Pangaea. Other minor oceans were shrinking and eventually closed - Rheic Ocean (closed by the assembly of South and North America), the small, shallow Ural Ocean (which was closed by the collision of Baltica and Siberia continents, creating the Ural Mountains) and Proto-Tethys Ocean (closed by North China collision with Siberia/Kazakhstania.
Climate
The early part of the Carboniferous was mostly warm; in the later part of the Carboniferous, the climate cooled. Glaciations in Gondwana, triggered by Gondwana's southward movement, continued into the Permian and because of the lack of clear markers and breaks, the deposits of this glacial period are often referred to as Permo-Carboniferous in age.
Rocks and coal
Carboniferous rocks in Europe and eastern North America largely consist of a repeated sequence of limestone, sandstone, shale and coal beds, known as "cyclothems" in the U.S. and "coal measures" in Britain. In North America, the early Carboniferous is largely marine limestone, which accounts for the division of the Carboniferous into two periods in North American schemes. The Carboniferous coal beds provided much of the fuel for power generation during the Industrial Revolution and are still of great economic importance.
The large coal deposits of the Carboniferous primarily owe their existence to two factors. The first of these is the appearance of bark-bearing trees (and in particular the evolution of the bark fiber lignin). The second is the lower sea levels that occurred during the Carboniferous as compared to the Devonian period. This allowed for the development of extensive lowland swamps and forests in North America and Europe. Some hypothesize that large quantities of wood were buried during this period because animals and decomposing bacteria had not yet evolved that could effectively digest the new lignin. Those early plants made extensive use of lignin. They had bark to wood ratios of 8 to 1, and even as high as 20 to 1. This compares to modern values less than 1 to 4. This bark, which must have been used as support as well as protection, probably had 38% to 58% lignin. Lignin is insoluble, too large to pass through cell walls, too heterogeneous for specific enzymes, and toxic, so that few organisms other than Basidiomycetes fungi can degrade it. It can not be oxidized in an atmosphere of less than 5% oxygen. It can linger in soil for thousands of years and inhibits decay of other substances. Probably the reason for its high percentages is protection from insect herbivory in a world containing very effective insect herbivores, but nothing remotely as effective as modern insectivores and probably much fewer poisons than currently. In any case coal measures could easily have made thick deposits on well drained soils as well as swamps. The extensive burial of biologically-produced carbon led to a buildup of surplus oxygen in the atmosphere; estimates place the peak oxygen content as high as 35%, compared to 21% today. This oxygen level probably increased wildfire activity, as well as resulted in insect and amphibian gigantism--creatures whose size is constrained by respiratory systems that are limited in their ability to diffuse oxygen.
In eastern North America, marine beds are more common in the older part of the period than the later part and are almost entirely absent by the late Carboniferous. More diverse geology existed elsewhere, of course. Marine life is especially rich in crinoids and other echinoderms. Brachiopods were abundant. Trilobites became quite uncommon. On land, large and diverse plant populations existed. Land vertebrates included large amphibians.
Life
Marine invertebrates
In the oceans the most important marine invertebrate groups are the foraminifera, corals, bryozoa, brachiopods, ammonoids, hederelloids and echinoderms (especially crinoids).
For the first time foraminifera take a prominent part in the marine faunas. The large spindle-shaped genus Fusulina and its relatives were abundant in what is now Russia, China, Japan, North America; other important genera include Valvulina, Endothyra, Archaediscus, and Saccammina (the latter common in Britain and Belgium). Some Carboniferous genera are still extant.
The microscopic shells of Radiolaria are found in cherts of this age in the Culm of Devonshire and Cornwall, and in Russia, Germany and elsewhere.
Sponges are known from spicules and anchor ropes, and include various forms such as the Calcispongea Cotyliscus and Girtycoelia, and the genus of unusual colonial glass sponges Titusvillia.
Both reef-building and solitary corals diversify and flourish; these include both rugose (e.g. Canina, Corwenia, Neozaphrentis), heterocorals, and tabulate (e.g. Chaetetes, Chladochonus, Michelinia) forms.
Conularids were well represented by Conularia
Bryozoa are abundant in some regions; the Fenestellids including Fenestella, Polypora, and the remarkable Archimedes, so named because it is in the shape of an Archimedean screw.
Brachiopods are also abundant; they include Productids, some of which (e.g. Gigantoproductus) reached very large (for brachiopods) size and had very thick shells, while others like Chonetes were more conservative in form. Athyridids, Spiriferids, Rhynchonellids, are Terebratulids are also very common. Inarticulate forms include Discina and Crania. Some species and genera had a very wide distribution with only minor variations.
Annelids such as Spirorbis and Serpulites are common fossils in some horizons.
Among the mollusca, the bivalves continue to increase in numbers and importance. Typical genera include Aviculopecten, Posidonomya, Nucula, Carbonicola, Edmondia, and Modiola
Conocardium is a common rostroconch.
Gastropods are also numerous, including the genera Murchisonia, Euomphalus, Naticopsis.
Nautiloid cephalopods are represented by tightly coiled nautilids, with straight-shelled and curved-shelled forms becoming increasingly rare. Goniatite Ammonoids are common.
Trilobites are rarer than in previous periods, represented only by the proetid group. A class of Crustacean Zooplankton known as Ostracods such as Cythere, Kirkbya, and Beyrichia was abundant.
Amongst the echinoderms, the crinoids were the most numerous. Dense submarine thickets of long-stemmed crinoids appear to have flourished in shallow seas, and their remains were consolidated into thick beds of rock. Prominent genera include Cyathocrinus, Woodocrinus, and Actinocrinus. Echinoids such as Archaeocidaris and Palaeechinus were also present. The Blastoids, which included the Pentreinitidae and Codasteridae and superficially resembled crinoids in the possession of long stalks attached to the seabed, attain their maximum development at this time.
Fish
Many fish inhabited the Carboniferous seas; predominantly Elasmobranchs (sharks and their relatives). These included some, like Psammodus, with crushing pavement-like teeth adapted for grinding the shells of brachiopods, crustaceans, and other marine organisms. Other sharks had piercing teeth, such as the Symmoriida |
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