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| Alleghenian–Hercynian | |
|---|---|
| Name | Alleghenian–Hercynian |
| Period | Late Paleozoic |
| Type | Orogeny |
| Region | Appalachians, Variscides, Ouachitas |
Alleghenian–Hercynian The Alleghenian–Hercynian orogeny denotes a suite of Late Paleozoic mountain-building events that affected the North American and Eurasian continental margins and interior, producing orogenic belts such as the Appalachians, the Variscides, and the Ouachitas, and involving interactions among plate margins including the Laurentia, Gondwana, and Armorica microcontinents during the assembly of Pangea. The term synthesizes regional nomenclature used in the literature by researchers affiliated with institutions such as the USGS, the GSA, and the BGS and appears in comparative tectonic studies alongside concepts advanced by scientists like E. Suess, A. Wegener, and A. Holmes.
The compound label unites Appalachian-stage descriptions from investigators at the Smithsonian Institution and USGS with European usage rooted in work by geologists at the BGS and the Geological Society of London, where the Variscan term originated, while continental reconstructions by teams at the IPGP and GFZ use correlated chronostratigraphic frameworks such as the Pennsylvanian and Permian to align stratigraphic units described by researchers from the University of Oxford, Harvard University, and Columbia University. Historical debates between proponents at the Royal Society and the American Philosophical Society over nomenclature echo methodological contrasts documented in syntheses from the IUGS.
The principal deformation phases are constrained to the Late Mississippian, Pennsylvanian, and Permian as established in radiometric studies by researchers at Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory, and integrated with biostratigraphic zonations refined by paleontologists at the Smithsonian Institution and Natural History Museum, London. Plate reconstructions produced by teams at Lamont–Doherty and the Potsdam Institute model the convergence of Laurentia, Gondwana, and intervening terranes such as Avalonia and Armorica, invoking processes parallel to those documented for the Caledonian orogeny and the Alleghanian orogeny in regional syntheses curated by the GSA and the BGS.
Mechanisms invoked include continent–continent collision, subduction rollback, slab breakoff, and lithospheric delamination discussed in numerical models from MIT, ETH Zurich, and Stanford University, with analogues drawn from studies of the Himalayas, Alps, and Cordillera. Thermomechanical simulations developed at Columbia University and the University of Cambridge integrate constraints from seismic tomography undertaken by collaborations among IRIS, USGS, and GFZ to resolve crustal shortening, thickening, and lateral extrusion that generated fold-and-thrust systems noted by field teams from the University of Tennessee, University of Pennsylvania, and the University of Munich.
In eastern North America the Appalachian orogen exhibits foreland basins and thrust belts studied by investigators at Penn State University and the U.S. Geological Survey, while in western Europe the Variscides show collisional suture zones and ophiolitic remnants mapped by researchers from the BGS, University of Barcelona, and Charles University in Prague. Peripheral belts such as the Ouachitas and the Cantabrian Mountains record transpressional regimes documented by fieldwork coordinated by the University of Arkansas, University of Leeds, and CSIC teams, and were correlated through stratigraphic compilations assembled by the IUGS and regional geological surveys like the Geological Survey of Canada.
Structural architectures comprise thin- and thick-skinned thrust systems, megafolds, and crustal-scale nappes characterized in seismic profiles from the USGS and the European Seismic Network, and in analogue experiments at ETH Zurich and CNRS. Metamorphic gradients ranging from greenschist to granulite facies have been dated using techniques refined at Max Planck Institute for Chemistry and Carnegie Institution for Science, with pressure–temperature–time paths interpreted by metamorphic petrologists at UCL, Scripps Institution of Oceanography, and the University of Bern to reconstruct burial and exhumation histories tied to collision and post-orogenic collapse phases described by researchers from the University of Bergen and University of Salamanca.
Paleogeographic maps synthesized by teams at Paleomap Project collaborators and the University of Chicago integrate sediment provenance studies using detrital zircon geochronology from laboratories at New Mexico Tech and Arizona State University, linking source areas across reconstructions that position Laurentia adjacent to Gondwana during Pangea assembly as argued in reconstructions by Ron Blakey and modelers at the University of Sydney and GFZ. Paleoclimatic indicators logged by researchers at the British Antarctic Survey and UCL further constrain terrestrial environments and glacio-eustatic influences on basin evolution during the Late Paleozoic.
Mineralization associated with Alleghenian–Hercynian tectonism includes coal in Appalachian basins studied by the USGS and Pennsylvania Geological Survey, metallogenic provinces bearing lead–zinc–barite in the Variscides documented by the BGS and Spanish Geological Survey (IGME), and orogenic gold and tin–tungsten mineralization explored by teams at University of Colorado and INRAP, with hydrocarbon potential assessed in foreland basins by energy research groups at Chevron, BP, and national geological surveys such as the Norwegian Petroleum Directorate.
Category:Orogenies