Definition of Avalonia
: a tectonic plate that was an independent continent about 500 million years ago and is currently divided between southwestern Great Britain and eastern North America A strip of the Maine coast south of Bangor is part of Avalonia. So too is eastern Massachusetts and all of Rhode Island. … Fossil trilobites found in outcrops at Braintree, Massachusetts, are also found in the Carolinas, the Canadian Maritime Provinces, southern Ireland, and parts of England and Wales—but nowhere else on Earth.— Chet Raymo and Maureen E. Raymo, Boston Globe, 11 Dec. 1988
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