Abstract

Paleomagnetic data from 104 sites (3 samples per site) in terrestrial sedimentary rocks of the Nacimiento Formation in the San Juan Basin were analyzed to determine a paleomagnetic pole for middle Paleocene time. Alternating-field demagnetization to 300-Oe peak field was sufficient to erase secondary viscous components. The mean direction of magnetization (inclination = 51.3°, declination = 343.9°) was calculated by averaging the site mean directions for the 42 normal polarity sites along with the antipoles of the site means of the 62 reversed polarity sites. The middle Paleocene pole position is at lat 75.9°N, long 147.7°E (δp = 2.7°, δm = 4.1°). The revised apparent polar wander path for North America shows a sharp turn for Late Cretaceous time that correlates with the onset of the Laramide orogeny.

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