Pennsylvanian System
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| Pennsylvanian System | |
|---|---|
| Name | Pennsylvanian System |
| Time start | 323.2 |
| Time end | 298.9 |
| Era | Paleozoic |
| Period | Carboniferous |
| Region | Global usage (chiefly North America) |
Pennsylvanian System The Pennsylvanian System denotes a formal stratigraphic interval within the Carboniferous that is widely used in North American lithostratigraphy and regional geology. It is recognized in correlation with international stages such as the Bashkirian, Moscovian, Kasimovian, and Gzhelian and appears in mapping programs conducted by agencies like the United States Geological Survey and the British Geological Survey. Major basin studies by institutions including the Pennsylvania Geological Survey and the University of Illinois at Urbana–Champaign employ the term alongside regional chronostratigraphic schemes such as those of the Appalachian Basin, Illinois Basin, and Midcontinent Rift.
Definition and Stratigraphic Position
The Pennsylvanian System is defined as the upper subsystem of the Carboniferous in North American usage, overlying the Mississippian and underlying strata correlated with the Permian in western sections; stratigraphic resolution is refined by work at units studied by the Geological Society of America and calibrated against sections in the Moscovian and Kasimovian type localities. Formal boundary definitions reference type sections examined by geologists affiliated with the Smithsonian Institution, the Royal Society, and university departments such as the Ohio State University and University of Kansas; regional chronostratigraphic charts from the International Commission on Stratigraphy guide correlations with sections from the Donets Basin, Pennine Coal Measures, and the Huangshan region.
Nomenclature and Regional Usage
Usage of the Pennsylvanian label varies among organizations: North American stratigraphers in the United States Geological Survey tradition employ the term, whereas many European workers prefer the subdivision into Westphalian, Stephanian, and other regional stages used by the British Geological Survey and the International Commission on Stratigraphy. Regional names like Allegheny Group, Pottsville Formation, and Pará Group are used by state surveys including the Pennsylvania Geological Survey and the Illinois State Geological Survey and by international bodies such as the Geological Survey of Canada and the Bureau of Economic Geology at the University of Texas at Austin.
Lithology and Depositional Environments
Pennsylvanian strata display cyclic lithologies including coal seams, interbedded sandstones, siltstones, shales, and marine limestones documented in basin analyses by teams at the University of Pittsburgh, Louisiana State University, and the University of Missouri. Depositional settings range from coastal plain and deltaic systems studied in the Appalachian Basin and Illinois Basin to open-marine shelves recorded in sections near the Ouachita Mountains, Ankeny Limestone exposures, and carbonate platforms examined by researchers at the California Institute of Technology. Cyclothems and parasequences pervasive in the record have been interpreted using models advanced by the Paleontological Society and case studies in the Black Warrior Basin and the Paraná Basin.
Paleontology and Biostratigraphy
Fossil assemblages characteristic of the interval include abundant plant groups such as Lepidodendron, Calamites, and Sigillaria alongside invertebrates like fusulinids, Productida, and brachiopods used in biostratigraphic zonation developed by the Palaeontological Association and researchers at the Natural History Museum, London. Vertebrate remains, including early amniotes documented by teams from the University of Chicago and the Field Museum, and tetrapod assemblages from the Joggins Fossil Cliffs and the Red Beds of Texas, contribute to paleoecological reconstructions. Palynological work by groups at the Universität Göttingen and the University of Sheffield refines correlations with European stages like the Westphalian and Asian sections such as those in the Tien Shan.
Chronostratigraphy and Correlation
Absolute and relative dating frameworks integrate radiometric constraints from volcanic ash beds analyzed at labs in the Scripps Institution of Oceanography and the Geological Survey of Japan with biostratigraphic markers recognized by the International Commission on Stratigraphy and the American Geophysical Union. Correlation efforts link North American units such as the Allegheny Group and Conemaugh Group to global stages—Bashkirian, Moscovian, Kasimovian, Gzhelian—through multidisciplinary studies involving the Royal Society of Edinburgh and the Chinese Academy of Sciences.
Economic Resources and Uses
Pennsylvanian strata host significant coal deposits exploited historically by companies like Consolidation Coal Company and regions administered by state agencies including the Pennsylvania Department of Environmental Protection and the West Virginia Geological and Economic Survey. Hydrocarbon reservoirs in sandstone units have been targeted by firms such as ExxonMobil and Chevron and evaluated in reports by the United States Energy Information Administration and the Energy Information Administration equivalents in Canada. Industrial minerals—clays, building stone, and limestone—are quarried for use by corporations like US Steel and local municipalities including Pittsburgh and St. Louis.
Regional Examples and Key Formations
Key North American formations include the Pottsville Formation, Allegheny Group, Conemaugh Group, and Black Hand Sandstone studied by state surveys like the Ohio Geological Survey and the Kentucky Geological Survey. International analogues and correlated units include the Westphalian coal measures of the United Kingdom, the Paraná Basin coal-bearing intervals in Brazil, and Carboniferous successions in the Donets Basin and the Ural Mountains examined by research teams from the Russian Academy of Sciences and the Universidade de São Paulo. Field localities such as the Joggins Fossil Cliffs (a UNESCO World Heritage Site) and exposures in the Anthracite Region, Pennsylvania provide classic sections used by scholars from institutions like the University of Cambridge and the University of Edinburgh for teaching and research.