Avalonia
noun
Av·a·lo·nia ˌa-və-ˈlō-nyə 
-nē-ə
geology
: 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
Chet Raymo and Maureen E. Raymo, Boston Globe, 11 Dec. 1988
Word History
Etymology
probably back-formation from Avalonian (by analogy with other paleogeographical entities such as Laurentia), as in Avalonian orogeny, Avalonian platform, etc., from Avalon Peninsula, Newfoundland + -ian
First Known Use
1979, in the meaning defined above