Kinematic history of the Narragansett Basin, Massachusetts and Rhode Island: Constraints on Late Paleozoic plate reconstructions

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Abstract
The formation of the Narragansett Basin of Rhode Island and Massachusetts and the polyphase deformation geometry of the Pennsylvanian‐age basin sediments can be explained by collision and strike slip interactions between an Avalonian microcontinent, the European‐North American plate, and the African plate. During the late Paleozoic, sinistral movement between an Avalonian microcontinent and the European‐North American plate resulted in formation of pull apart basins. Subsequently, Africa moved toward North America along an east‐west trending, dextral megashear zone and collided with the eastern margin of southern North America. The Narragansett Basin is located on the Avalonian microcontinent near the suture with the North American continent and in the transition zone between the megashear and the collision tectonic regimes. The basin shape, stratigraphy, and sedimentary relationships can be explained by the coalescence of two composite grabens which formed at different times. The thicker northern graben is only affected by one deformation, whereas the southern graben shows evidence of four distinct phases of postrifting deformation. The first two coaxial folding deformations of the basin sediments are attributed to the closure of the basin complex during collision of Africa and North America. The third and fourth deformations are interpreted as sinistral R′ riedal and dextral shears, respectively, associated with the east‐west trending megashear system. A prograde Barrovian metamorphic front started in the western portion of the southern graben slightly after the first deformation and migrated northward and eastward, where it is synchronous with the second deformation.