Abstract

The tectonostratigraphic record of the Avalon terrane in southern New Brunswick is interpreted as that of a Wilson cycle that followed the Grenvillian and preceded the opening of lapetus. Development of a late Precambrian continental shelf is attributed to the ?Cadomian ocean whose initial subduction at ∼800 Ma led to platform collapse, regional metamorphism, and minor mafic to ultramafic plutonism, in response to back-arc extension and crustal separation. Oblique subduction of the resulting back-arc basin at ∼600–630 Ma produced calcalkaline plutonism and cogenetic volcanism that ended in dextral transtension and the emplacement of a bimodal dike complex. Initial rifting of lapetus, which isolated this record from cratonic North America, is recorded in Eocambrian redbeds and bimodal volcanics and produced a Cambro-Ordovician overlap sequence bearing Acado-Baltic fauna.

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