Variscan orogeny

Both words were descriptive terms of strike directions observed by geologists in the field, variscan for southwest to northeast, hercynian for northwest to southeast.

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.

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.

In southern Iberia it is marked by a classic strike-slip suture zone between very distinct suspect terranes, and clear evidence can be seen of ductile shearing between high-grade metamorphic rocks and lower grade sedimentary rocks in a wide belt north of the Algarve and extending into the northernmost part the autonomous region of Andalusia and southern Extremadura.

[8][9] In the Czech Republic and southwestern Poland the Bohemian Massif is the eastern end of the unmodified Variscan belt of crustal deformation in Europe.

[10] The Variscan was contemporaneous with the Acadian and Alleghenian orogeny in the United States and Canada, responsible for forming the Ouachita and Appalachian Mountains.

[12][13] The Variscan orogeny involved a complicated heterogeneous assembly of different microplates and heterochronous collisions, making the exact reconstruction of the plate tectonic processes difficult.

They collided in the Caledonian orogeny and formed the Caledonide mountains of North America, Greenland, the British Isles and Norway.

Seafloor spreading to the south of Avalonia pushed the latter into north Laurentia and thrust up the northern Appalachian Mountains in the acadian phase of the Caledonian orogeny.