THE HERCYNIAN OROGENY: The Dawn of PangaeaOnce upon a time… in the lower Paleozoic (say before aroun
THE HERCYNIAN OROGENY: The Dawn of PangaeaOnce upon a time… in the lower Paleozoic (say before around 400 million years ago), there was a scattering of continental tectonic plates upon the face of the Earth. In the mid to late Paleozoic (from ~ 400 to about 300 million years ago), these plates amalgamated to form the super-continent of Pangaea. The geologic event held responsible for this gathering of the continents into one giant continent is called The Hercynian and/or the Variscan Orogeny.An orogeny is an assortment of active geologic processes that work in tandem and result in the building of a mountain range. Today’s ongoing orogenies usually involve two tectonic plates: the plates are in collision (as is India mushing into Asia and building the Himalayas) or one plate is “subducted” beneath the other plate (as for the construction of the Andes above the zone where the Nazca plate is underriding the South American Plate). The Hercynian Orogeny apparently was a more complex affair: essentially the southern continental group (Gondwana) was heading for the northern continental group (given the name Laurussia or Euramerica), but in doing so numerous tectonic fragments were involved, all moving in such a way as to ram one into another. The result seems to be a juxtaposition of continental crusts separated by “suture zones,” essentially the mishmash of material caught up between the continental remnants.While terminology varies between calling this orogeny the Hercynian or Variscan, the marvelous folds produced within the suture zones are famous as Variscan folding, while the continental granites of this mid-late Paleozoic age are usually referred to as “Hercynian.” (I don’t know why. Some folk are sensitive to terminology and I would rather not argue about it.) Anyway, Variscan folds can be seen in a 3000 km zone extending from Ireland, Portugal, Spain, Great Britain, France and on through the Balkans and Carpathians. Great granite massifs are found in the zone, and perhaps one of the greatest is in Bavaria…Which brings us to the lovely photo by my colleague Bob Myhill, showing us the Hercynian granite at Plattengipfel, Germany, at sunrise, reminding us of the dawn of a former age at the birth of Pangaea…Annie RPhoto with thanks to Bob Myhill.Further knowledge:http://myweb.tiscali.co.uk/geologyofcornwall/Variscan.htmhttp://www.britannica.com/EBchecked/topic/262841/Hercynian-orogenic-belthttp://link.springer.com/article/10.1007%2FBF01821154http://www.sciencedirect.com/science/article/pii/S1342937X13000981__ -- source link
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