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The Carboniferous Period.
The fifth period of the Paleozoic Era. The Carboniferous Period spanned from about 355 million years to about 295 million years ago. The rocks that formed during this time interval are known as the Carboniferous System; they include a wide variety of sedimentary, igneous, and metamorphic rocks. Sedimentary rocks in the lower portion of the Carboniferous are typically carbonates, such as limestones and dolostones, and locally some evaporites. The upper portions of the system are usually composed of cyclically repeated successions of sandstones, coals, shales, and thin limestones. See also Sedimentary rocks.
The economic importance of the Carboniferous is evident in its name, which refers to coal, the important energy source that fueled the industrialization of northwestern Europe in the early 1800s and led to the Carboniferous being one of the first geologic systems to be studied in detail. Carboniferous coals formed in coastal and fluvial environments in many parts of the world. Petroleum, another important energy resource, accumulated in many Carboniferous marine carbonate sediments, particularly near shelf margins adjacent to basinal black shale source rocks. In many regions the cyclical history of deposition and exposure has enhanced the permeability and porosity of the shelfal rocks to make them excellent petroleum reservoirs. The limestones of the Lower Carboniferous are extensively quarried and used for building stone, especially in northwestern Europe and the central and eastern United States. See also Coal; Petroleum.
The base of the Carboniferous is placed at the first appearance of the conodont Siphonodella sulcata, a fossil that marks a widely recognized biozone in most marine sedimentary rocks. The reference locality for this base is an outcrop in Belgium. The top of the Carboniferous is placed at the first appearance of the conodont Streptognathus isolatus a few meters below the first appearance of the Permian fusulinacean foraminiferal zone of Sphaeroschwagerina fusiformis. The reference locality is in the southern Ural region in Kazakhstan. The equivalent biozone is at the base of Pseudoschwagerina in North America. See also Conodont; Fusulinacea.
The International Subcommission on Carboniferous Stratigraphy reached general agreement in the 1970s and 1980s that the Carboniferous would be divided into two parts: a Lower Carboniferous Mississippian Subsystem and an Upper Carboniferous Pennsylvanian Subsystem. The two Carboniferous subsystems are subdivided into a number of series and stages that are variously identified in different parts of the world, based on biostratigraphic evidence using evolutionary successions in fossils or overlapping assemblage zones.
Perhaps the strongest of the many ecological factors that controlled biotic distributions were the paleogeographic changes within the Carboniferous that were brought about by the initial assembling of the supercontinent Pangaea and the associated mountain-building activities, which greatly modified climate, ocean currents, and seaways. In the Early Carboniferous, a nearly continuous equatorial seaway permitted extensive tropical and subtropical carbonate sedimentation on the shelves and platforms in North America, northern and southern Europe, Kazakhstan, North and South China, and the northern shores of the protocontinent Gondwana (such as northern Africa).
The gradual collision of northern Gondwana against northern Europe-North America (also called Euramerica or Laurussia) started the formation of the supercontinent of Pangaea. See also Continental drift; Continents, evolution of; Paleogeography; Plate tectonics.
An additional ramification of the formation of Pangaea was the beginning of very extensive glaciation in the Southern Hemisphere polar and high-latitude regions of the supercontinent. Glacial deposits are also known from smaller continental fragments that were at high paleolatitudes in the Northern Hemisphere. The Earth's climate cooled, tropical carbonate-producing areas became restricted toward the Equator, and eustatic sea-level fluctuations became prominent in the sedimentary record. See also Glacial epoch.
During the Carboniferous, life evolved to exploit fully the numerous marine and nonmarine aquatic environments and terrestrial and aerial habitats. Single-cell protozoan foraminifers evolved new abilities to construct layered, calcareous walls. Insects have remarkable evolutionary histories during the Carboniferous. They adapted to flight and dispersed into many terrestrial and fresh-water habitats. Vertebrates also evolved rapidly. Although acanthodian fish declined from their Devonian peak, sharklike fishes and primitive bony fishes adapted well to the expanded environments and the new ecological food chains of the Carboniferous. Some sharklike groups invaded fresh-water habitats, where they were associated with coal swamp deposits. Carboniferous amphibians evolved rapidly in several directions. The earliest were the labyrinthodont embolomeres, which had labyrinthodont teeth and were mainly aquatic. Another significant labyrinthodont group was the rhachitomes, which originated in the Early Carboniferous and became abundant, commonly reaching about 1 m (3 ft) or more; they were widespread in terrestrial habitats during the Late Carboniferous and Permian. Primitive reptiles evolved from one of the embolomere amphibian lineages during the Late Carboniferous. They formed the basal stock from which all other reptiles have evolved including the earliest mammallike reptiles in the Late Carboniferous. During the Late Carboniferous, early reptiles coexisted with several advanced amphibian groups which shared at least some, but probably not all, of their reptilelike characters.
Terrestrial plants also showed major diversification of habitats and the evolution of important new lineages during the Carboniferous. Initially, Early Carboniferous plants were predominantly a continuation of latest Devonian groups; however, they were distinguished in part by their large sizes with many arborescent lycopods and large articulates, and pteridosperms (seed ferns) and ferns became increasingly abundant and varied. By the Late Carboniferous, extensive swamps formed along the broad, nearly flat coastal areas; and these coal-forming environments tended to move laterally across the coastal plain areas as the sea level repeatedly rose. Other coal-forming marshes were common in the floodplains and channel fills of the broad rivers of upper delta distributary systems. During the Late Carboniferous, primitive conifers appeared and included araucarias, which became common in some, probably drier ecological habitats. See also Paleobotany; Paleozoic.
A period of Palaeozoic time stretching approximately from 345 to 280 million years bp. This period can be subdivided into the Mississippian and the Pennsylvanian periods. During this period, massive limestones and coal measures were formed.
The noun has one meaning:
Meaning #1:
from 280 million to 345 million years ago
Synonym: Carboniferous period
The Carboniferous is a major division of the geologic timescale 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 (ICS 2004). As with most older geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by 5–10 million years. The Carboniferous is named for the extensive coal beds of that age found in Western Europe. The first third of the Carboniferous is called the Mississippian epoch, and the remainder is called the Pennsylvanian. Conifer trees appeared in this important and well-known time period.
The Carboniferous is usually broken into Pennsylvanian (later) and Mississippian (earlier) Epochs. The Faunal stages from youngest to oldest, together with some of their subdivisions, are:
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.[1] 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.[2] These conditions apparently had little effect in the deep tropics, where lush coal swamps flourished within 30 degrees of the northernmost glaciers.[3]
A mid-Carboniferous drop in sea-level precipitated a major marine extinction, one that hit crinoids and ammonites especially hard.[4] This sea-level drop and the associated unconformity in North America separate the Mississippian period from the Pennsylvanian period.[5]
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.[6] 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.
The early part of the Carboniferous was mostly warm; in the later part of the Carboniferous, the climate
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.[7] 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. 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.[1] 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.
In the oceans the most important groups are the foraminifera, corals, bryozoa, brachiopods, ammonoids, echinoderms (especially crinoids), and Chondrichthyes (sharks and their relatives).
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 unusual colonial glass sponge 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 rare, represented only by the proetid group. Ostracods such as Cythere, Kirkbya, and Beyrichia are 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 sea-bed, attain their maximum development at this time.
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; some, the petalodonts, had peculiar cycloid cutting teeth. Most of the sharks were marine, but the Xenacanthida invaded fresh waters of the coal swamps. Among the bony fish, the Palaeonisciformes found in coastal waters also appear to have migrated to rivers. Sarcopterygian fish were also prominent, and one group, the Rhizodonts, reached very large size.
Most species of Carboniferous marine fish have been described largely from teeth, fin spines and dermal ossicles, with smaller freshwater fish preserved whole.
Freshwater fishes were abundant, and include the genera Ctenodus, Uronemus, Acanthodes, Cheirodus, and Gyracanthus.
Early Carboniferous land plants were very similar to those of the preceding Late Devonian, but new groups also appeared at this time.
The main Early Carboniferous plants were the Equisetales (Horse-tails), Sphenophyllales (vine-like plants), Lycopodiales (Club mosses), Lepidodendrales (scale trees), Filicales (Ferns), Medullosales (informally included in the "seed ferns", an artificial assemblage of a number of early gymnosperm groups) and the Cordaitales. These continued to dominate throughout the period, but during late Carboniferous, several other groups, Cycadophyta (cycads), the Callistophytales (another group of "seed ferns"), and the Voltziales (related to and sometimes included under the conifers), appeared.
The Carboniferous lycophytes of the order Lepidodendrales, which are cousins (but not ancestors) of the tiny club-moss of today, were huge trees with trunks 30 meters high and up to 1.5 meters in diameter. These included Lepidodendron (with its fruit cone called Lepidostrobus), Halonia, Lepidophloios and Sigillaria. The roots of several of these forms are known as Stigmaria.
The fronds of some Carboniferous ferns are almost identical with those of living species. Probably many species were epiphytic. Fossil ferns and "seed ferns" include Pecopteris, Cyclopteris, Neuropteris, Alethopteris, and Sphenopteris; Megaphyton and Caulopteris were tree ferns.
The Equisetales included the common giant form Calamites, with a trunk diameter of 30 to 60 cm and a height of up to 20 meters. Sphenophyllum was a slender climbing plant with whorls of leaves, which was probably related both to the calamites and the lycopods.
Cordaites, a tall plant (6 to over 30 meters) with strap-like leaves, was related to the cycads and conifers; the catkin-like inflorescence, which bore yew-like berries, is called Cardiocarpus. These plants were thought to live in swamps and mangroves. True coniferous trees (Waichia, of the order Voltziales) appear later in the Carboniferous, and preferred higher drier ground.
Freshwater Carboniferous invertebrates include various bivalve molluscs that lived in brackish or fresh water, such as Anthracomya, Naiadiles, and Carbonicola; diverse crustaceans such as Bairdia, Carbonia, Estheria, Acanthocaris, Dithyrocaris, and Anthrapalaemon.
The Eurypterids were also diverse, and are represented by such genera as Eurypterus, Glyptoscorpius, Anthraconectes, Megarachne (originally misinterpreted as a giant spider) and the specialised very large Hibbertopterus. Many of these were amphibious.
Frequently a temporary return of marine conditions resulted in marine or brackish water genera such as Lingula, Orbiculoidea, and Productus being found in the thin beds known as marine bands.
Fossil remains of air-breathing insects, myriapods and arachnids are known from the late Carboniferous, but so far not from the early Carboniferous. Their diversity when they do appear however show that these arthropods were both well developed and numerous. Their large size can be attributed to the moistness of the environment (mostly swampy fern forests) and the fact that there was a 36% higher oxygen concentration in Earth's atmosphere than today, requiring less effort for respiration and allowing arthropods to grow larger. Among the insect groups are the Syntonopterodea (relatives of present-day mayflies), the abundant and often large sap-sucking Palaeodictyopteroidea, the huge predatory Protodonata (griffinflies), the diverse herbivorous "Protorthoptera", and numerous basal Dictyoptera (ancestors of cockroaches). Many insects have been obtained from the coalfields of Saarbruck and Commentry, and from the hollow trunks of fossil trees in Nova Scotia. Some British coalfields have yielded good specimens: Archaeoptitus, from the Derbyshire coalfield, had a spread of wing extending to more than 35 cm; some specimens (Brodia) still exhibit traces of brilliant wing colors. In the Nova Scotian tree trunks land snails (Archaeozonites, Dendropupa) have been found.
Carboniferous amphibians were diverse and common by the middle of the period, more so than they are today; some were as long as 6 meters, and those fully terrestrial as adults had scaly skin.[8] They included a number of basal tetrapod groups classified in early books under the Labyrinthodontia. These had long bodies, a head covered with bony plates and generally weak or undeveloped limbs. The largest were over 2 meters long. They were accompanied by an assemblage of smaller amphibians included under the Lepospondyli, often only about 15 cm long. Some Carboniferous amphibians were aquatic and lived in rivers (Loxomma, Eogyrinus, Proterogyrinus); others may have been semi-aquatic (Ophiderpeton, Amphibamus) or terrestrial (Dendrerpeton, Hyloplesion, Tuditanus, Anthracosaurus).
One of the greatest evolutionary innovations of the Carboniferous was the amniote egg, which allowed for the further exploitation of the land by certain tetrapods. These included the earliest Sauropsid reptiles (Hylonomus), and the earliest known synapsid (Archaeothyris). These small lizard-like animals quickly gave rise to many descendants. The amniote egg allowed these ancestors of all later birds, mammals, and reptiles to reproduce on land by preventing the desiccation, or drying-out, of the embryo inside. By the end of the Carboniferous period, the amniotes had already diversified into a number of groups, including protorothyridids, captorhinids, aeroscelids, and several families of pelycosaurs.
Because plants and animals were growing in size and abundance in this time (e.g., Lepidodendron), land fungi diversified further. Marine fungi still occupied the oceans.
In the middle Carboniferous, an extinction event occurred that was probably caused by climate change. A less intense extinction event also occurred by the end of Carboniferous.
This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.
| Carboniferous period | |||||
|---|---|---|---|---|---|
| Mississippian | Pennsylvanian | ||||
| Lower/Early | Middle | Upper/Late | Lower/Early | Middle | Upper/Late |
| Tournaisian | Viséan | Serpukhovian | Bashkirian | Moscovian | Kasimovian | Gzhelian |
| Paleozoic era | |||||
|---|---|---|---|---|---|
| Cambrian | Ordovician | Silurian | Devonian | Carboniferous | Permian |
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