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| fifth period of the Paleozoic era of geologic time (see Geologic Timescale,
table), from 350 to 290 million years ago. |
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| Historical Geology of the Period |
| The Carboniferous period was marked by vast, coal-forming swamps (see
also bog) and a succession of changes in the earth’s surface that,
continuing into the Permian period, ended the Paleozoic era. The Carboniferous
is often split into two divisions, the Mississippian and the Pennsylvanian;
in the United States the break in the geologic sequence is so sharp that
each division is commonly considered an independent period. |
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| The Lower Carboniferous Period |
| In the Lower Carboniferous, or Mississippian, period, the submersion—on
several occasions—of the interior of North America under shallow seas
resulted in the formation of limestone, shale, and sandstone. In the Appalachian
region, especially in Pennsylvania, great deposits of sandstone and shale
were laid down by the erosion products from the eastern coastal highlands.
In the far west the Rocky Mt. region was covered by shallow seas that deposited
the Madison and Redwall limestones of the Grand Canyon. |
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| The Lower Carboniferous in Europe was a period of submergence and great
volcanic activity. E of the Rhine, shales, sandstones, and conglomerates
were deposited; and in Russia, the Coal Measures formed. The close of the
Lower Carboniferous was marked by mountain building in New Brunswick, Nova
Scotia, the S Appalachian region, the SW United States, and Europe. |
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| The Upper Carboniferous Period |
| In the Upper Carboniferous, or Pennsylvanian, period, there was at least
one great submergence. In the E United States great deltas of sediments,
now represented by the Pottsville conglomerate, were formed during the early
Pennsylvanian. In Kansas, Nebraska, Arkansas, and Texas, the Pennsylvanian
beds are chiefly shale, sandstone, and coal; over the Cordilleran (Rocky
Mountain) region, marine limestone, with little coal; on the Pacific coast
from California to Alaska, limestone and shale. The sea level also oscillated
during the period and caused the formation of great marshes with extensive
vegetation that was later transformed into coal, with Pennsylvanian strata
containing the largest U.S. coal deposits. The Pennsylvanian coal fields
of North America include the anthracite field of E Pennsylvania; the Appalachian
field, from Pennsylvania to Alabama; the Michigan field; the eastern interior
field, in Indiana, Illinois, and Kentucky; the western interior and southwestern
field, stretching from Iowa to Texas; the Rhode Island field; and the Acadian
field of SE Canada. |
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| In the Upper Carboniferous of Western Europe, the Millstone Grit (the
equivalent to the Pottsville conglomerate) is followed by the Coal Measures,
which include the Welsh, English, Belgian, Westphalian, and Saar Basin fields.
In the Mediterranean region and parts of Asia, the Upper Carboniferous
environment resembled that of W North America. |
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| The Upper Carboniferous was a period of marked disturbances caused by
collisions of crustal plates. Gondwanaland, the supercontinent containing
the continents of Africa and S America, had formed; Euramerica, part of Europe
and N America, had fused into a continent to the north; and Angara, today’s
Asia, was also to the north of Gondwanaland. In Europe the Paleozoic Alps
were thrust up; in Asia, the Altai and the Tian Shan; in North America, the
Arbuckle and Wichita mts. and the ancestral S Rockies. The Indian peninsula
became an active site of deposition; in the Himalayan geosyncline and much
of China, mountain building was dominant. Crustal movements in the Andean
geosyncline of South America affected the pattern of sedimentation over much
of the continent. |
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| Evolution of Plant and Animal Life |
| The plant life of the Carboniferous period was extensive and
luxuriant, especially during the Pennsylvanian. It included ferns
and fernlike trees; giant horsetails, called calamites; club mosses, or lycopods,
such as Lepidodendron and Sigillaria; seed ferns; and cordaites, or primitive
conifers. Land animals included primitive amphibians, reptiles (which first
appeared in the Upper Carboniferous), spiders, millipedes, land snails,
scorpions, enormous dragonflies, and more than 800 kinds of
cockroaches. The inland waters were inhabited by fishes, clams,
and various crustaceans; the oceans, by mollusks, crinoids, sea urchins,
and one-celled foraminifera. |
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