Pennsylvanian
Encyclopedia
The Pennsylvanian is, in the ICS
geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous
Period. It lasted from roughly . As with most other geochronologic
units, the rock
beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain by a few million years. The Pennsylvanian is named after the American state of Pennsylvania
, where rocks with this age are widespread.
The division between Pennsylvanian and Mississippian comes from North American stratigraphy. In North America
, where the early Carboniferous
beds are primarily marine limestone
s, the Pennsylvanian was in the past treated as a full fledged geologic period between the Mississippian and the Permian
. In Europe
, the Mississippian and Pennsylvanian are one more-or-less continuous sequence of lowland continental deposits and are grouped together as the Carboniferous Period. The current internationally used geologic timescale of the ICS
gives the Mississippian and Pennsylvanian the rank of subperiods, subdivisions of the Carboniferous Period.
s were diverse and common; some were several meters long as adults. The collapse of the rainforest ecology
in the mid Pennsylvanian (between the Moscovian and the Kasimovian) removed many amphibian species that did not survive as well in the cooler, drier conditions. Reptiles, however, prospered due to specific key adaptations. One of the greatest evolutionary innovations of the Carboniferous was the amniote
egg, which allowed for the further exploitation of the land by certain tetrapod
s. These included the earliest sauropsid
reptiles (Hylonomus
), and the earliest known synapsid
(Archaeothyris
). These small lizard-like animals quickly gave rise to many descendants. Reptiles underwent a major evolutionary radiation, in response to the drier climate that proceeded the rainforest collapse.
follows the Russia
n subdivision into four stages:
North American subdivision is into five stages, but not precisely the same, with additional (older) Appalachian series names following:
The Virgilian or Conemaugh corresponds to the Gzhelian plus the uppermost Kasimovian.
The Missourian or Monongahela corresponds to the rest of the Kasimovian.
The Desmoinesian or Allegheny corresponds to the upper half of the Moscovian.
The Atokan or upper Pottsville corresponds to the lower half of the Moscovian.
The Morrowan corresponds to the Bashkirian.
In the European subdivision, the Carboniferous is divided into two epochs: Dinantian
(early) and Silesian (late). The Silesian starts earlier than the Pennsylvanian and is divided in three ages:
International Commission on Stratigraphy
The International Commission on Stratigraphy , sometimes referred to by the unofficial "International Stratigraphic Commission" is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigraphy, geological, and geochronological matters on a global...
geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
Period. It lasted from roughly . As with most other geochronologic
Geochronology
Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...
units, the rock
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain by a few million years. The Pennsylvanian is named after the American state of Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
, where rocks with this age are widespread.
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, where the early Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
beds are primarily marine limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
s, the Pennsylvanian was in the past treated as a full fledged geologic period between the Mississippian and the Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
. In Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, the Mississippian and Pennsylvanian are one more-or-less continuous sequence of lowland continental deposits and are grouped together as the Carboniferous Period. The current internationally used geologic timescale of the ICS
International Commission on Stratigraphy
The International Commission on Stratigraphy , sometimes referred to by the unofficial "International Stratigraphic Commission" is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigraphy, geological, and geochronological matters on a global...
gives the Mississippian and Pennsylvanian the rank of subperiods, subdivisions of the Carboniferous Period.
Vertebrates
AmphibianAmphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s were diverse and common; some were several meters long as adults. The collapse of the rainforest ecology
Rainforest collapse
Rainforest collapse refers to the actual past and theoretical future destruction of rainforests through a process of habitat fragmentation to the point where little rainforest biome is left, only to survive in isolated refugia....
in the mid Pennsylvanian (between the Moscovian and the Kasimovian) removed many amphibian species that did not survive as well in the cooler, drier conditions. Reptiles, however, prospered due to specific key adaptations. One of the greatest evolutionary innovations of the Carboniferous was the amniote
Amniote
The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...
egg, which allowed for the further exploitation of the land by certain tetrapod
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
s. These included the earliest sauropsid
Sauropsida
Sauropsida is a group of amniotes that includes all existing reptiles and birds and their fossil ancestors, including the dinosaurs, the immediate ancestors of birds...
reptiles (Hylonomus
Hylonomus
Hylonomus was a very early reptile. It lived 312 million years ago during the Late Carboniferous period.It is the earliest unquestionable reptile ....
), and the earliest known synapsid
Synapsid
Synapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...
(Archaeothyris
Archaeothyris
Archaeothyris was a very early mammal-like reptile, which lived in the late Carboniferous period. Dated to 306 million years ago, it is the oldest undisputed synapsid known....
). These small lizard-like animals quickly gave rise to many descendants. Reptiles underwent a major evolutionary radiation, in response to the drier climate that proceeded the rainforest collapse.
Subdivisions
The Pennsylvanian has been variously subdivided. The international timescale of the ICSInternational Commission on Stratigraphy
The International Commission on Stratigraphy , sometimes referred to by the unofficial "International Stratigraphic Commission" is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigraphy, geological, and geochronological matters on a global...
follows the Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n subdivision into four stages:
- BashkirianBashkirianThe Bashkirian is in the ICS geologic timescale the lowest stage or oldest age of the Pennsylvanian, the youngest subsystem of the Carboniferous...
(oldest) - MoscovianMoscovian (Carboniferous)The Moscovian is in the ICS geologic timescale a stage or age in the Pennsylvanian, the youngest subsystem of the Carboniferous. The Moscovian age lasted from 311.7 ± 1.1 to 306.5 ± 1.0 Ma, is preceded by the Bashkirian and is followed by the Kasimovian...
- KasimovianKasimovianThe Kasimovian is an geochronologic age or chronostratigraphic stage in the ICS geologic timescale. It is the third stage in the Pennsylvanian , lasting from 306.5 ± 1.0 to 303.9 ± 0.9 Ma. The Kasimovian stage follows the Moscovian and is followed by the Gzhelian.-Name and definition:The Kasimovian...
- GzhelianGzhelianThe Gzhelian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the youngest stage of the Pennsylvanian, the youngest subsystem of the Carboniferous. The Gzhelian lasted from 303.9 ± 0.9 to 299.0 ± 0.8 Ma...
(youngest)
North American subdivision is into five stages, but not precisely the same, with additional (older) Appalachian series names following:
- Morrowan stage, corresponding with the middle and lower part of the Pottsville Group (oldest)
- Atokan stage, corresponding with the upper part of the Pottsville group
- Desmoinesian stage, corresponding with the Allegheny Group
- Missourian stage, corresponding with the Conemaugh Group
- VirgilianVirgilian seriesThe Virgilian series is the most recent part of the Pennsylvanian epoch in the North American geologic classification series. In the older Appalachian classification system, this series was known as the Monongahela group...
stage, corresponding with the Monongahela Group (youngest)
The Virgilian or Conemaugh corresponds to the Gzhelian plus the uppermost Kasimovian.
The Missourian or Monongahela corresponds to the rest of the Kasimovian.
The Desmoinesian or Allegheny corresponds to the upper half of the Moscovian.
The Atokan or upper Pottsville corresponds to the lower half of the Moscovian.
The Morrowan corresponds to the Bashkirian.
In the European subdivision, the Carboniferous is divided into two epochs: Dinantian
Dinantian
Dinantian is the name of a series or epoch from the Lower Carboniferous system in Europe. It can stand for a series of rocks in Europe or the time span in which they were deposited....
(early) and Silesian (late). The Silesian starts earlier than the Pennsylvanian and is divided in three ages:
- NamurianNamurianThe Namurian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 326 and 313 Ma . It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Namurian is named for the Belgian city and province of Namur where strata of this age...
(corresponding to SerpukhovianSerpukhovianThe Serpukhovian is in the ICS geologic timescale the uppermost stage or youngest age of the Mississippian, the lower subsystem of the Carboniferous. The Serpukhovian age lasted from 328.3 Ma tot 318.1 Ma...
and early Bashkirian) - WestphalianWestphalian (stage)The Westphalian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 313 and 304 Ma . It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Westphalian is named for the region of Westphalia in western Germany where strata...
(corresponding to late Bashkirian, Moskovian and Kasimovian) - StephanianStephanian (stage)The Stephanian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 304 and 299 Ma . It is a subdivision of the Carboniferous system or period and the regional Silesian series...
(corresponding to Gzelian).
External links
- The Late Carboniferous a Time of Great Coal Swamps, Paleomap project. World map from this time period.
- The Carboniferous - 354 to 290 Million Years Ago, University of California Museum of PaleontologyUniversity of California Museum of PaleontologyThe University of California Museum of Paleontology is a paleontology museum located on the campus of the University of California, Berkeley....
. Information on stratigraphies, localities, tectonics, and life. - The Pennsylvanian Epoch of the Carboniferous Period: 318 to 299 Mya, Paleos.com
- US Geological Survey comparison of time scales