Variscan orogeny
The Variscan or Hercynian orogeny was a geologic mountain-building event caused by Late
.Nomenclature
The name Variscan comes from the Medieval
Hercynian, on the other hand, derives from the
One of the pioneers in research on the Variscan fold belt was the German geologist Franz Kossmat, establishing a still valid division of the European Variscides in 1927.[2]
The other direction, Hercynian, for the direction of the Harz Mountains in Germany, saw a similar shift in meaning. Today, Hercynian is often used as a synonym for Variscan but is somewhat less used than the latter.[3] In the United States, it is used only for European orogenies; the contemporaneous and genetically linked mountain-building phases in the Appalachian Mountains have different names.[4][5]
The regional term Variscan underwent a further meaning shift since the 1960s. Geologists generally began to use it to characterize late Paleozoic fold-belts and orogenic phases having an age of approximately 380 to 280 Ma.
Some publications use the term Variscan for fold belts of even younger age,[6] deviating from the meaning as a term for the North American and European orogeny related to the Gondwana-Laurasia collision.
Distribution
The North American and European Variscan Belt includes the mountains of Portugal and Spain (Galicia, and Pyrenees), southwestern Ireland (i.e. Munster), Cornwall, Devon, Pembrokeshire, the Gower Peninsula and the Vale of Glamorgan. Its effects are present in France from Brittany, below the Paris Basin to the Ardennes, the Massif Central, the Vosges and Corsica.
The Variscan Belt reappears in
In the Czech Republic and southwestern Poland the
The Variscan was contemporaneous with the
Formation
The Variscan orogeny involved a complicated heterogeneous assembly of different microplates and heterochronous collisions, making the exact reconstruction of the plate tectonic processes difficult. Plate convergence that caused the Caledonian orogeny in the Silurian continued to form the Variscan orogeny in the succeeding Devonian and Carboniferous Periods. Both orogenies resulted in the assembly of a super-continent, Pangaea, which was essentially complete by the end of the Carboniferous.
In the Ordovician Period, a land mass, which has been named Gondwana (present day South America, Africa, Antarctica, Arabia, the Indian subcontinent, Zealandia and Australia), straddled the space between the South Pole and the Equator on one side of the globe. Off to the west were three other masses: Laurentia, Siberia and Baltica, located as if on the vertices of a triangle. To the south of them was a large archipelago, the terrane Avalonia, rifted off the north Gondwana margin in early Ordovician.
By the end of the
In late Devonian and in the Carboniferous the archipelago Armorica of southern Europe, which had rifted off Gondwana after Avalonia later in the Ordovician, was pushed into Avalonia, creating a second range, the North American/European Variscan, to the east of the Caledonide/Appalachian. The collision of Gondwana proper with Laurussia followed in the early Carboniferous, when the Variscan belt was already in place and actively developing.
By the end of the Carboniferous, Gondwana had united with Laurussia on its western end through northern South America and northwestern Africa. Siberia was approaching from the northeast, separated from Laurussia only by shallow waters. Collision with Siberia produced the
Era, animals could move without oceanic impediment from Siberia over the North Pole to Antarctica over the South Pole. In the Mesozoic Era, rifting and subsequent opening of the Atlantic split Pangaea. As a consequence, the Variscan Belt around the then periphery of Baltica ended up many hundreds of miles from the Appalachians.Notes
- ^ Based on Matte 2001 and Ziegler 1990
- ^ Kossmat, F. (1927). "Gliederung des varistischen Gebirgsbaus". Abh. Sächs. Geol. L.-A. 1. Leipzig: 1–39.
- ^ Google search on December 29, 2007: ca. 44.500 for Variscan orogeny, ca. 15.000 Hercynian orogeny. In German: 1.170 for "variszische Orogenese", 154 for "herzynische Orogenese".
- ^ Tectonics of the Devonian. Website of University of California Museum of Paleontology. Accessed on December 29, 2007.
- ^ "The Hercynian Orogeny". Historical Geology, University of North Texas.
- ^ Lee, K. Y. (1989). "Geology of petroleum and coal deposits in the North China Basin, Eastern China". USGS Bulletin 1871. Archived from the original on 2019-09-13. Retrieved 2017-09-17. Table 1, p. 3.
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: CS1 maint: postscript (link) - S2CID 195334509.
- S2CID 128688878.
- ^ Tectonic Map of the western Tethysides Archived 2008-04-23 at the Wayback Machine. Institute of Geology and Paleontology of the University of Lausanne, Switzerland. Accessed on December 29, 2007.
- . Retrieved 1 November 2015.
- ^ Paleotethys. Paleogeographic reconstructions for the Devonian and Carboniferous Archived 2011-06-08 at the Wayback Machine. Tethyan Plate Tectonic Working Group of the University of Lausanne, Switzerland. Accessed on December 29, 2007.
- ^ Paleogeographic configuration Lower Carboniferous. Paleomap Project by C.Scotese. Accessed on December 29, 2007.
Further reading
- Matte, P. (2001). "The Variscan collage and orogeny (480 ±290 Ma) and the tectonic definition of the Armorica microplate: a review". Terra Nova. 13 (2): 122–128. S2CID 129727506.
- ISBN 978-90-6644-125-5.
- von Raumer, J.; Stampfli, G.M.; Borel, G.D.; Bussy, F. (2002). "The organisation of pre-Variscan basement areas at the north-Gondwanan margin" (PDF). International Journal of Earth Sciences. 91 (1): 35–52. S2CID 131617311.
- von Raumer, J.; Stampfli, G.M.; Bussy, F. (2003). "Gondwana-derived microcontinents - the constituents of the Variscan and Alpine collisional orogens". Tectonophysics. 365 (1–4): 7–22. .
- Stampfli, GM; Borel, GD (2004). "The TRANSMED Transects in Space and Time: Constraints on the Paleotectonic Evolution of the Mediterranean Domain". In Cavazza W; Roure F; Spakman W; Stampfli GM; Ziegler P (eds.). The TRANSMED Atlas: the Mediterranean Region from Crust to Mantle. Springer Verlag. ISBN 978-3-540-22181-4.
External links
- Christopher R. Scotese, Paleomap Project:
- Ronald Blakey, Colorado Plateau Geosystems Inc: Europe in the Late Carboniferous Archived 2015-09-22 at the Wayback Machine