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Pennsylvanian
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The Pennsylvanian is an epoch in the geologic timescale or a series in the stratigraphic column. It is a subdivision of the Carboniferous period lasting from roughly to Ma (million years ago). 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.
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Encyclopedia
The Pennsylvanian is an epoch in the geologic timescale or a series in the stratigraphic column. It is a subdivision of the Carboniferous period lasting from roughly to Ma (million years ago). 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 state of Pennsylvania, where rocks from this epoch are widespread.
The division between Pennsylvanian and Mississippian comes from North American stratigraphy. In North America, where the early Carboniferous beds are primarily marine limestones, 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 epochs, subdivisions of the Carboniferous period.
All modern classes of fungi were present in the Late Carboniferous (Pennsylvanian epoch).
Subdivisions
The Pennsylvanian has been variously subdivided. The international timescale of the ICS follows the Russian subdivision into four stages:
- Bashkirian (oldest)
- Moscovian
- Kasimovian
- Gzhelian (youngest)
North American subdivision is also into four 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
- 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 (late). The Silesian starts earlier than the Pennsylvanian and is divided in three ages:
- Namurian (corresponding to Serpukhovian and early Bashkirian)
- Westphalian (corresponding to late Bashkirian, Moskovian and Kasimovian)
- Stephanian (corresponding to Gzelian).
External links
- Provides a picture of the world from this time period.
- Information on stratigraphies, localities, tectonics, and life.
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- US Geological Survey comparison of time scales
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