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Abstract

Mesozoic and early Cenozoic magmatism in eastern North America produced distinct provinces with characteristic igneous and tectonic styles. This discussion is arranged in order of age and province size and is primarily descriptive in nature. Some of the igneous events are not well dated and thorough chemical and petrographic analyses may also be lacking. Our aim is to outline present knowledge of the provinces, gathered from many scattered published and unpublished studies, and to synthesize some of the more important aspects of the rocks and events that produced them. More definitive models will eventually be developed, which we believe can show fundamental relationships between lithospheric tectonism and resulting intraplate-to-rift zone magmatism in eastern North America.

Exposed flood basalts and sills of early Jurassic age are confined mainly to grabens of the "Newark" rift system. The "Newark" rift system encompasses a series of fault-bound basins extending from Florida to Nova Scotia (Fig. 1). Newark-type basins occur farther north (east Greenland, Surlyk, 1978a, b) and east (Morocco-Portugal, Manspeizer, 1981), indicating that Mesozoic rifting followed both the Caledonian and Hercynian sutures (Ziegler, 1975). "Newark" rift zones consistently step eastward as one proceeds north and south from Virginia. Their regional distribution thus mimics that of the ocean floor anomalies, which show a dominant sense of right lateral offset to the north and left lateral offset to the south of the Bermuda flowline (Sundvik and others, 1984).

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