Pennsylvanian (geology)
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The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the
ICS ICS may refer to: Computing * Image Cytometry Standard, a digital multidimensional image file format used in life sciences microscopy * Industrial control system, computer systems and networks used to control industrial plants and infrastructure ...
geologic timescale The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located in a previously establish ...
, the younger of two subperiods (or upper of two
subsystems A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure A structure is an arr ...
) of the
Carboniferous The Carboniferous ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisi ...
Period. It lasted from roughly . As with most other
geochronologic Image:Geological time spiral.png, 300px, An artistic depiction of the major events in the history of Earth Geochronology is the science of Chronological dating, determining the age of rock (geology), rocks, fossils, and sediments using signatures i ...
units, the
rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the way in w ...
beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain by a few hundred thousand years. The Pennsylvanian is named after the U.S. state of
Pennsylvania Pennsylvania ( ) ( pdc, Pennsilfaani), officially the Commonwealth of Pennsylvania, is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, and Appalachia, Appalachian regions of the ...

Pennsylvania
, where the coal-productive beds of this age are widespread. The division between Pennsylvanian and Mississippian comes from North American stratigraphy. In North America, where the early
Carboniferous The Carboniferous ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisi ...
beds are primarily marine
limestone Limestone is a common type of carbonate rock, carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science), crystal forms of calcium carbonate (). Limestone forms ...

limestone
s, the Pennsylvanian was in the past treated as a full-fledged geologic period between the Mississippian and the
Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous period million years ago (Mya), to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleo ...
. 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 ICS may refer to: Computing * Image Cytometry Standard, a digital multidimensional image file format used in life sciences microscopy * Industrial control system, computer systems and networks used to control industrial plants and infrastructure ...
gives the Mississippian and Pennsylvanian the rank of subperiods, subdivisions of the Carboniferous Period.


Life


Fungi

All modern
classes Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently f ...
of
fungi A fungus (plural: fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as ...

fungi
have been found in rocks of Pennsylvanian age.


Invertebrates

The major forms of life at this time were the arthropods. Due to the high levels of oxygen, arthropods were far larger than modern ones. ''
Arthropleura ''Arthropleura'' (greek language, Greek for ''jointed ribs'') is a genus of extinct millipede arthropods that lived in what is now northeastern North America and Scotland around 345 to 295 million years ago, from the Viséan stage of the lower C ...

Arthropleura
'', a giant millipede relative, was a common sight and the giant dragonfly ''Meganeura'' "flew the skies".


Vertebrates

Amphibians were diverse and common; some were several meters long as adults. The Carboniferous Rainforest Collapse, 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. Amniotes, 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 tetrapods. These included the earliest Sauropsida, sauropsid reptiles (''Hylonomus''), and the earliest known synapsid pelycosaurs (''Archaeothyris''). Small lizard-like animals quickly gave rise to many descendants. Amniotes underwent a major evolutionary radiation, in response to the drier climate that followed the rainforest collapse. For some reason, pelycosaurs were able to larger sizes before reptiles could, and this trend continued until the P-T extinction event, during which their cynodont descendants became smaller and nocturnal bottleneck, nocturnal, as the reptilian archosaurs took over. Most pre-rainforest collapse tetrapods remained smaller, probably due to the land being primarily occupied by the gigantic millipedes, scorpions, and flying insects. After the rainforest collapse, the giant arthropods ceased to exist, allowing amniote tetrapods to achieve larger sizes.


Subdivisions

The Pennsylvanian has been variously subdivided. The international timescale of the
ICS ICS may refer to: Computing * Image Cytometry Standard, a digital multidimensional image file format used in life sciences microscopy * Industrial control system, computer systems and networks used to control industrial plants and infrastructure ...
follows the Russian subdivision into four stages:Cohen ''et al.'' 2013 *Bashkirian (oldest) *Moscovian (Carboniferous), Moscovian *Kasimovian *Gzhelian (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), Missourian stage, corresponding with the Conemaugh Group *Virgilian series, Virgilian 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 (early) and Silesian (series), Silesian (late). The Silesian starts earlier than the Pennsylvanian and is divided in three ages: *Namurian (corresponding to Serpukhovian and early Bashkirian) *Westphalian (stage), Westphalian (corresponding to late Bashkirian, Moskovian and Kasimovian) *Stephanian (stage), Stephanian (corresponding to Gzelian).


References


External links


The Late Carboniferous a Time of Great Coal Swamps
Paleomap project. World map from this time period.

University of California Museum of Paleontology. 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
{{Geological history, p, p, state=collapsed Pennsylvanian (geology), Pennsylvanian geochronology, Carboniferous geochronology, *02 Geological epochs Carboniferous United States, *