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Avalonia was an ancient microcontinent or terrane. The name is derived from the Avalon Peninsula in Newfoundland.
Development
In the early Cambrian, the supercontinent Pannotia broke up and Avalonia drifted off northwards from Gondwana. This independent movement of Avalonia started from a latitude of about 60° South. The eastern end of Avalonia collided with Baltica, a continental plate occupying the latitudes from about 30°S to 55°S, as the latter slowly rotated anticlockwise towards it. This happened at the end of the Ordovician and during the early Silurian. This collision is represented by the Caledonian folding.
In the late Silurian and lower Devonian, the combined Baltica and Avalonia collided progressively, with Laurentia, beginning with the long extremity of Avalonia which is now attached to America. The result of this was the formation of Euramerica. At the completion of this stage, the site of Britain was at 30°S and Nova Scotia at about 45°S.
In the Permian, the new continent and another terrane from Gondwana then came together trapping Avalonia between them and adding Iberia/Armorica to Euramerica. This collision is represented by the Variscan folding. This was happening at around the Equator during the later Carboniferous.forming Pangaea in such a way that Avalonia was near its centre. It was as part of this stage that the Iberia and Avalonia came together.
In the Jurassic, Pangaea split into Laurasia and Gondwana, with Avalonia as part of Laurasia. In the Cretaceous, Laurasia broke up into North America and Eurasia with Avalonia split between them.
Consequences
In the modern world, we see Avalonia as forming the basic structure of the Ardennes of Belgium and north-eastern France, north Germany, north-western Poland, England, Wales, south-eastern Ireland, the south-western edge of the Iberian Peninsula, the Avalon Peninsula, much of Nova Scotia, southern New Brunswick and parts of New England. See map 2, Acadian Orogeny and The Acadian orogeny.
The Avalonian part of Britain almost exactly coincides with England and Wales. Part of this which had formed an island in the Carboniferous, so affecting the disposition of coalfields, is known by names such as the 'London-Brabant Island'. Its bulk had an effect on the geological structure between the Ardennes and the English Midlands by influencing the subsequent crustal folding resulting from the Variscan collision.
Maps
- * These maps show the relative positions of the terranes and continental plates at various stages in the Ordovician, Silurian and Devonian respectively. The names shown are in their German forms.
External links
- Article about Avalonia at Palaeos.Com (licensed under Attribution-NonCommercial 1.0 complete with pictures)
- The context of Avalonia's movements
Geology of England | Geology of Wales | Historical continents | Paleozoic | Mesozoic | Natural history of Nova Scotia
"Avalonia"