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Chapter 21: Paleomagnetism of North America; The craton, its margins, and the Appalachian Belt

By
Rob Van der Voo
Rob Van der Voo
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Published:
January 01, 1989

This chapter examines, with a new set of reliability criteria, the data base of paleomagnetic poles available for the North American craton. If it is deemed desirable that all paleopoles used in the construction of an apparent polar wander path meet these criteria, then these criteria can be considered as very stringent; indeed, only four Phanerozoic results pass all seven criteria. On the other hand, more than 115 pass three or more of the criteria. Thus, the usefulness of these criteria lies in the flexibility with which they can be applied, the ease with which researchers can apply their own weighting of importance to the data base, and the ease with which a given polar wander path can be constructed (and constrained) for different purposes with different reliability filters.

The polar wander paths, so constructed, are only as interesting as the use that is being made of them. In this review, paleopoles obtained from the thrust belt margins of the craton are discussed in terms of rotations of thrust sheets and blocks such as in the Wyoming-Montana overthrust belt and the Colorado Plateau, whereas the Appalachian belt is discussed in terms of displaced and exotic terranes. New insights in the cratonic data base, particularly as they pertain to the now-recognized ubiquitous remagnetizations, have clarified some previously controversial issues, such as the hypothesis of a displaced Acadia terrane that was postulated to have moved during Carboniferous time. With the presently available reference poles, displacements can now be documented only for pre-Middle Devonian time. The Avalon basement terranes, in particular, have yielded a reliable data set that reveals their allochthonous nature for early Paleozoic time. It is paleomagnetically plausible to postulate that Avalon and Hercynian Europe constituted an Armorica plate that collided with the North American craton by Early Devonian time. Ordovician and older paleopoles from Avalon show high southerly paleolatitudes and have strong affinities with those for Hercynian Europe, as well as Gondwanaland, suggesting that Armorica was located adjacent to Gondwanaland before it broke off in Ordovician time and traveled northward.

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GSA Memoirs

Geophysical Framework of the Continental United States

L. C. Pakiser
L. C. Pakiser
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Walter D. Mooney
Walter D. Mooney
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Geological Society of America
Volume
172
ISBN print:
9780813711720
Publication date:
January 01, 1989

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