Abstract

The bedded succession in Newport, Rhode Island, consists of the metavolcanic Price's Neck formation and the older metasedimentary Newport formation. The Newport formation consists of turbidites, sandstone and conglomerate, slate, phyllite, bedded ash, and olistostromes. The Price's Neck formation consists of agglomeratic breccia, conglomerate, coarse to fine tuff, and graded tuffite merging into tuffaceous sedimentary rock.

Both sequences have been affected by two principal fold-generating deformations. The Price's Neck formation was first folded into upright to overturned folds (F1), whereas the Newport formation was folded into overturned to recumbent folds. In the Price's Neck formation, the F1 folds trend east-west to north-northeast-south-southwest, Whereas the F2 folds trend approximately east-west. In the main outcrop area the F1 folds in the Newport formation are dominantly north-south trending, are strongly overturned toward the east, and in the west are recumbent and subisoclinal to isoclinal. The second deformation produced a low-lying cleavage and relatively small folds that verge toward the east. The difference in the style of folding is attributed to ductility contrast between the rocks of the two stratigraphic sequences.

The Newport granite, which intrudes the Price's Neck and Newport formations, has a metamorphic aureole. The granite was emplaced prior to the F2 movements but after the F1 movements. The succession therefore is late Precambrian in age, because the granite is about 600 m.y. old. The deformation of the sediments may be attributed to the “Avalonian orogeny” that is manifested in Anglesey, Wales, and northern France as the Cadomian. There are strong similarities between Anglesey and Newport in lithologies, stratigraphic succession, and plutonic history.

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