CARBONIFEROUS SYSTEM. One of the main divisions of the Paleozoic group of rocks, comprising all strata that lie between the De vonian and Triassic systems. The name was first used in England, because of the coal-scams contained in the strata, a characteristic now known to be of almost world-Nxide importance. The rocks of this system include a vast series of sandstones, shales. conglomerates, limestones, and beds of coal, which are of variable thickness and more or less interbedded. There is seldom any unconfo•mity between the Carboniferous and underlying Devonian rocks in either Europe or America, and where isolated examples are known, as in parts of Nova Scotia, New Bruns wick, Great Britain, and Bohemia, they indi cate local disturbances. Coincident with this absence of any great stratigraphical break, there is also a gradual transition from the De vonian to the Carboniferous faunas. The rocks often show a basin-shaped arrangement, and in some areas, as in northeastern Pennsylvania, there is intense folding: hut still there are thousands of equate in flee in China. western North America, and Russia which are under lain by nearly horizontal strata.
The different types of Carboniferous rocks mentioned above are divisible into turn general groups—viz.: (1) :\larine sediments, usually littlest 011VS, containing many invertebrate re mains, such as corals, mollusks, enerinites, etc. The abundance of coral remains in some of them lead us to suppose that they represent fossil coral reefs. These Carboniferous limestones sometimes assume great thickness, as in Great Britain and western North America. (2) Shal low-water deposits. such as sandstones. C011 g101ne 1%1 s, or shales. deposited in shore waters or estuaries. These shallow estuaries or lagoons, by the formation of land across their mouth, often became converted into seacoast swamps in which there was a profuse growth of tall plants. These swamps were often of enormous extent, hut at times the long-continued swamp growth became temporarily interrupted by the deposition of clay washed in either by flooded rivers or by the muddy waters of the sea break ing in. Or, again. the sinking the area below
the ocean level may have caused the arcumula tinn of much sediment over the swamp growth.
Subsequently the plant accumulation became changed to coal, and the clay to shale. We find records of these changes at the present day in the alternating coal and shale seams.
Carboniferous rocks are widely distributed over the globe, underlying wide. area in North America. South America. Europe, China, Africa, and Australia. In classifying the rocks of these areas, the divisions of the first order are the same, but the smaller divisions are commonly local ones. The first order division consists in grouping the Carboniferous into: (1) Sub-Carboniferous, known also as Lower and Mississippian.
(2) Carboniferous proper, Coal :Measures. or Pennsylvanian.
(3) Permian, Upper Carboniferous, or Dyas.
The Permian is considered by some European geologists as a separate system, coequal with the Carboniferous: in the :Mississippi Valley it is, however, inseparable from the upper non-coal hearing fossiliferous limestones of the :Mississip pian stage. In the United States the Carbonifer ous sections along the Appalachians and in the nssissippi Valley are divided as follows: Penn sylvania—Sub-Carboniferous, (I) Pocono sand stone: (2) Mauch Chunk sandstone and shale; Carboniferous. (1 ) Pottsville conglomerate or millstone grit (2) Lower productive measures, including coal, shale, and sandstones: (3) Lower barren measures, including sandstones and shales; (4) Upper productive measures, includ ing coal, shale, and sandstones; Permian or Upper barren measures. :Mississippi Valley — Sub-Carboniferous, (1) Kinderhook: (2) Osage, including (a) Burlington: (h) Keokuk: (c) arsaw: (3) St. Louis group: (4) Chester or Kaskaskia group. Carboniferous, (1) Millstone grit ; (2) Coal measures: Permian.