Pennsylvanian

Pennsylvanian
Name	Pennsylvanian
Color	#7FB3D5
Time start	323.2
Time end	298.9
Unit	Subperiod
Era	Carboniferous
Period	Carboniferous
Used in	International

Pennsylvanian The Pennsylvanian is a formal subperiod of the Carboniferous known for extensive coal-bearing strata, diverse terrestrial faunas, and major tectono-sedimentary basins across what are now North America, Europe, and parts of Asia. It succeeds the Mississippian and precedes the Permian, recording critical shifts in paleoclimate, sea level, and biotic composition during the Late Paleozoic Ice Age. Its highly fossiliferous deposits have been central to studies involving Charles Lyell-era stratigraphy, industrial coal exploitation by entities such as the Pennsylvania Railroad era companies, and modern chronostratigraphic frameworks developed by organizations like the International Commission on Stratigraphy.

Definition and Etymology

The name derives from the state of Pennsylvania, where classic coal measures were described in 19th-century surveys by geologists linked to institutions such as the U.S. Geological Survey, the British Geological Survey, and regional academies. Early stratigraphers including William Smith and later workers like James Hall and Elias Huntington helped formalize the Pennsylvanian concept within the broader Carboniferous chronostratigraphy. Debates over nomenclature involved comparative work between the Coal Measures Group of Great Britain, the Westphalian stages of Germany, and American series defined in basins exploited by companies like Bethlehem Steel Corporation and surveyed by the Geological Society of London.

Geological Time and Stratigraphy

The Pennsylvanian is formally bounded at approximately 323.2 to 298.9 million years ago in the International Chronostratigraphic Chart endorsed by the International Union of Geological Sciences. Stratigraphically, it includes regional stages such as the Bashkirian, Moscovian, Kasimovian, and Gzhelian recognized across Eurasia, and correlates with North American series defined in basins like the Appalachian Basin, the Midcontinent Rift, and the Ancestral Rocky Mountains-related basins. Key type sections and reference profiles are preserved in outcrops such as the Pocono Formation and the Allegheny Formation in stratotypes used by university departments including University of Pennsylvania and Pennsylvania State University. Radiometric constraints derived from interbedded volcanic ash beds tied to labs at institutions like the United States Geological Survey and the Geological Survey of Canada refine age models and allow correlation with marine stages used in studies by researchers affiliated with the Museum für Naturkunde, Berlin and the Natural History Museum, London.

Paleoenvironments and Climate

During the Pennsylvanian, plate configurations involving Laurussia and Gondwana promoted formation of extensive tropical and subtropical coal swamps, deltaic complexes, and epeiric seas. Climatic oscillations associated with the Late Paleozoic Ice Age influenced glacioeustatic cycles recorded in cyclothems first characterized in the Midcontinent of United States and in the North Sea Basin. These cycles produced alternating marine limestones, shales, and coal seams preserved in formations investigated by teams from Stanford University, Yale University, and the University of Glasgow. Continental settings hosted peat-accumulating wetlands later studied in palynological work by researchers at Smithsonian Institution and in isotopic studies led by groups at ETH Zurich.

Paleontology and Fossil Fauna

Fossil assemblages of the Pennsylvanian are famed for lush lycopsid forests including Lepidodendron and Sigillaria, diverse sphenopsids such as Calamites, and early seed ferns like Medullosa. Vertebrate faunas include primitive synapsids represented in collections at the American Museum of Natural History and early reptiliomorphs documented by researchers at the University of Chicago and the Field Museum of Natural History. Invertebrates and marine faunas such as Ammonoidea, Crinoidea, and brachiopods occur in offshore facies correlated with assemblages housed at the Natural History Museum, London and the National Museum of Natural History (Smithsonian). Trace fossils and ichnofossils from sites studied by the Paleontological Society and described by paleontologists like Richard Fortey and M. J. Benton inform behavior, while plant-insect interaction records tied to work at Carnegie Museum of Natural History and University of Kansas Natural History Museum show early complex ecosystems.

Economic Importance and Resources

The Pennsylvanian hosts the majority of economically significant coal seams that fueled the industrial revolutions of United Kingdom, United States, and Germany, and that supported industries including United States Steel Corporation, Royal Dutch Shell, and regional mining companies. Major coalfields such as the Appalachian Basin coalfields, the Donets Basin, and the Silesian Coal Basin yield bituminous and anthracite deposits exploited by corporations and national energy programs. Beyond coal, Pennsylvanian strata contain reservoirs of hydrocarbons in basin plays explored by companies like ExxonMobil, BP, and Chevron Corporation, as well as economically important ironstone and carbonate resources used by firms such as ArcelorMittal and chemical feedstock industries. Environmental legacies from extraction have been addressed in policy frameworks involving agencies such as the Environmental Protection Agency and reclamation projects coordinated with regional universities.

Regional Correlation and Global Context

Correlation of Pennsylvanian sequences integrates regional chronostratigraphic schemes from North America, Europe, and Russia with global frameworks advanced by the International Commission on Stratigraphy and synthesized in compilations by the Paleobiology Database and national surveys. Paleogeographic reconstructions by teams at institutions like the University of Chicago and University of Texas at Austin place Pennsylvanian basins within tectonic episodes including the Alleghanian orogeny and the assembly of Pangaea. Global environmental perturbations recorded in Pennsylvanian strata—sea-level changes, glaciation events, and carbon-cycle shifts—are subjects of interdisciplinary research linking paleoclimatologists at Columbia University and geochemists at Scripps Institution of Oceanography to paleontologists at major museums and societies.

Category:Carboniferous