Finnmarkian, Athollian, Caledonian Orogenies
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Euramerica showing the Caledonian orogeny
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The branches of the Caledonian/Acadian belts at the end of the Caledonian orogeny (Early Devonian). Present-day coastlines are in gray.
The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic. The Paleozoic era spanned from roughly 542 to 251 million years ago (ICS, 2004), and is subdivided into six geologic periods; from oldest to youngest they are: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.
Finnmarkian orogeny affected northern Norway in the early palaeozoic era. In the late Ordovician period, Avalonia collided with Baltica creating the Tornquist Margin. This corresponds to the suture of the north German-Polish Caledonides. By the end of the Ordovician the Tornquist Sea had been eliminated. The Tornquist-Tesseyre fault system also had its beginnings in the orogeny closing the Tornquist Sea. Baltica subducted below Avalonia.
The Atthollian Orogeny was a collision between the Scottish Highlands and a Midland Valley area which very likely created the Highland Boundary Fault.
During the late Silurian period Baltica then collided with Laurentia which is named the Scandian phase of the Caledonian Orogeny. Baltica was subducted below Laurentia forming the Caledonian Belt. The Caledonian Orogeny caused the closure of the Iapetus Ocean when the continents and terranes of Laurentia, Baltica and Avalonia collided. The combined mass of the three continents formed a "new" continent: Laurussia or Euramerica. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian, roughly 490–390 Ma. The basement formations of the North Sea were roughly formed during this Caledonian geosynclinal stage of the Cambrian - Devonian eras. The Caledonian mountains range helped create the ‘Old Red Sandstone’ continent at the joining of the tectonic plates. The Rheic Ocean began to open to the south.
Read more about this topic: Geology Of The North Sea