Tectonic significance of dikes of Westerly Granite, southeastern Connecticut and southwestern Rhode Island

Abstract

Undeformed Early Permian Westerly Granite dikes cut gneisses of the southeastern New England Avalon zone along coastal southeastern Connecticut and adjacent Rhode Island. Most dikes dip southward at a low angle. The Westerly dikes were emplaced in relatively warm rock penecontemporaneously with the Narragansett Pier Granite during a narrow time interval shortly after cessation of pervasive Alleghanian ductile deformation but probably before final localized movement on major shear zones. The gentle dips indicate subhorizontal release at the end stage of the Alleghanian compressive event. Doming, intrusion of granite, and subsequent rapid uplift and cooling are attributed to the underplating of Avalonian crust by an African plate during the Alleghanian. -Author