Pennsylvanian subperiod

Pennsylvanian subperiod
Name	Pennsylvanian subperiod
Time start mya	323.2
Time end mya	298.9
Color	#89CFF0
Preceding	Mississippian subperiod
Following	Permian period
Era	Carboniferous period

Pennsylvanian subperiod The Pennsylvanian subperiod is a formal chronostratigraphic interval of the Carboniferous period characterized by widespread coal deposition, glacioeustatic sea-level changes, and the diversification of terrestrial ecosystems. It encompasses major stratigraphic units and tectonic events recorded across North America, Europe, Asia, and Gondwana-derived terranes, and it is integral to understanding Paleozoic paleogeography, basin evolution, and the early radiation of amniotes.

Definition and Chronostratigraphy

The Pennsylvanian subperiod was defined through stratigraphic work in the United States Geological Survey and by stratigraphers associated with the International Commission on Stratigraphy and regional bodies such as the Geological Society of America and the British Geological Survey. Its boundaries are defined by chronostratigraphic stages correlating to global stages used by the International Chronostratigraphic Chart and tie to biostratigraphic markers used by researchers from institutions like the Smithsonian Institution and the Natural History Museum, London. Correlations employ radiometric dates from igneous units studied by geochronologists at universities such as University of California, Berkeley and University of Oxford and integrate paleomagnetic data gathered by teams at the Scripps Institution of Oceanography and the Max Planck Institute for Chemistry.

Geology and Paleoenvironments

Pennsylvanian depositional systems record interactions between tectonics related to the Alleghenian orogeny, Variscan orogeny, and Hercynian orogeny and glacial episodes linked to the Late Paleozoic Ice Age. Basin analyses by researchers from Ohio State University and University of Michigan document cyclothems and clastic wedges tied to foreland basins adjacent to orogens such as the Appalachian Mountains and the Central Pangean Mountains. Sea-level reconstructions, informed by studies at the United States Geological Survey and the British Geological Survey, indicate repeated transgressions and regressions that produced complex facies mosaics across platforms like the Illinois Basin, Midcontinent Rift System, and Paris Basin.

Paleontology and Key Faunas

Fossil assemblages from Pennsylvanian strata include diverse invertebrate faunas, early amniote lineages, and tetrapod radiations documented by paleontologists at the American Museum of Natural History, Carnegie Museum of Natural History, and Natural History Museum, London. Iconic taxa and groups studied across museums and universities include representatives cited in collections at the Field Museum and Smithsonian Institution that illuminate evolutionary patterns found in formations such as the Mazon Creek fossil beds, Hamilton Group, and Joggins Fossil Cliffs. Research by teams from Yale University and the University of Chicago has clarified the ecology of arthropods, mollusks, and brachiopods preserved in marine shelves adjacent to deltas feeding into basins like the Permian Basin precursor systems.

Paleobotany and Coal Formation

Pennsylvanian floras dominated by lycopsids, sphenopsids, ferns, and early gymnosperms produced the extensive peatlands that later formed coal seams exploited in regions administered by bodies like the U.S. Bureau of Mines and companies such as Consol Energy. Studies by paleobotanists at Royal Botanic Gardens, Kew and University of Göttingen document genera including members of the Lepidodendrales and Calamites preserved in the Carboniferous coal measures of the Donets Basin, Silesian Basin, and Sydney Basin. Coal petrography and basin modeling performed at the International Energy Agency and petroleum geology groups at Statoil and BP connect peat accumulation to autogenic landscape evolution in deltas and coastal mires influenced by glacioeustatic cycles.

Regional Stratigraphy and Correlations

Regional stratigraphic frameworks for the Pennsylvanian have been developed for North America, Europe, Asia, and Australasia by mapping agencies including the Geological Survey of Canada, Geological Survey of Japan, and Geological Survey of India. Correlations link North American cyclothems to European sequences in the United Kingdom and Belgium, and to marine successions in the Russian Platform and China via biostratigraphy and isotope stratigraphy practiced at institutions such as the Institute of Geology and Paleontology, Nanjing and the Paleontological Institute, Moscow. Key regional units include the Pottsville Formation, Allegheny Formation, Upper Silesian Coal Basin, and the Kasimovian–Gzhelian equivalent sequences used by stratigraphers at the University of Warsaw and Charles University.

Economic Importance and Resources

The Pennsylvanian is economically significant for its coal, hydrocarbons, and industrial minerals exploited by corporations and regulated by authorities such as the U.S. Energy Information Administration and the Department of Energy (United States). Major mining and energy provinces include the Appalachian Basin, Illinois Basin, Donets Basin, and the Silesian Coal Basin, which have been investigated by petroleum geologists at firms like ExxonMobil and Chevron and by mining engineers trained at the Colorado School of Mines. Petrographic and geochemical studies from laboratories at Imperial College London and Massachusetts Institute of Technology inform resource assessments and environmental remediation overseen by agencies including the Environmental Protection Agency.

History of Study and Nomenclature

The term "Pennsylvanian" originated in 19th-century stratigraphic practice in the United States and was formalized through work by geologists associated with the U.S. Geological Survey and academics at institutions like University of Pennsylvania and Harvard University. European correlations were advanced by figures linked to the British Association for the Advancement of Science and the Prussian Geological Survey, while Soviet and Chinese stratigraphers integrated regional nomenclature via organizations such as the Academy of Sciences of the USSR and the Chinese Academy of Sciences. Ongoing revisions and international standardization involve the International Union of Geological Sciences and the International Commission on Stratigraphy, reflecting decades of fieldwork published in outlets like the Journal of Geology and the Geological Society Special Publications.

Category:Carboniferous subperiods