Abstract

It has been suggested that during the lower Paleozoic the Appalachian Piedmont Province formed not as part of North America, but on the south or east side of the Iapetus Ocean. The results of a previous paleomagnetic study of the Arden pluton from the Piedmont of northern Delaware are in agreement with this hypothesis. For the present study, several metamorphic and igneous rocks were sampled across a wide area of the northern Delaware Piedmont. The Late Ordovician poles determined in this study, like the Arden pluton pole, lie close to their sites and do not agree with Ordovician paleopoles for cratonic North America. Tilting of the sampled rocks after the acquisition of magnetization is considered unlikely because the same steep direction is found in rocks collected over a wide area. The interpretation of these results is that the Piedmont of northern Delaware formed as part of the African plate and later became sutured to North America when the Iapetus Ocean closed and Pangea was assembled.

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