Early Rifting in the Narragansett Basin, Massachusetts–Rhode Island: Evidence from Late Devonian Bimodal Volcanic Rocks

• Published in: The Journal of geology 2003-09, Vol.111 (5), p.597-604
• Main Authors: Thompson, Margaret D., Hermes, O. Don
• Format: Article
• Language: English
• Subjects: Basalt; Basement rocks; Coal; Conglomerates; Geological Notes; Geology; Plate tectonics; Plutons; Rhyolite; Sediments; Shear zones; Stone; Subsidence; Tectonics; Volcanic rocks
• ISSN: 0022-1376; 1537-5269
• DOI: 10.1086/376768

The basal Wamsutta Formation of the Narragansett Basin, Massachusetts–Rhode Island, contains \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $373\pm 2$ \end{document} Ma rhyolite that is unexpectedly 60 m.yr. older than sedimentary strata containing late Pennsylvanian floras higher in the basin fill. The transitional alkalic geochemistry of the rhyolite and associated basalt signifies Late Devonian rifting pre‐dating major basin subsidence. Surface rifting was accompanied by voluminous alkalic intrusions of the 380–370 Ma Scituate Igneous Suite into Neoproterozoic basement west of the basin and by ductile extension along shear zones confined to the pluton and neighboring units. The Maritimes Basin and adjoining areas in Atlantic Canada experienced a similar mid‐Paleozoic history.