North American Apparent Polar Wander, Plate Motion and Left-oblique Convergence: Late Jurassic - Early Cretaceous Orogenic Consequences

The North American apparent polar wander (APW) path indicates an episode of unusually rapid absolute northward motion of western North America between 150 and 135 Ma. During this time the northward component of absolute motion of points along the Washington-Oregon-California coast was in excess of 150 km/m.y. and perhaps as high as 230 km/m.y. We believe that such high absolute northward velocity for North America probably ensures that relative motions of oceanic plates and terranes influenced by them were to the south at this time. The inception of rapid northward motion and left-oblique convergence was abrupt and should be recorded in the geology of the western Cordillera. It is tempting to correlate this period of unusual Pacific basin-North American interaction with the “Nevadan orogeny” in the Klamath Mountains as well as with left-lateral strike-slip structures such as the Pine Nut fault and Bear Mountains fault zone. Significant differences exist between North American plate motion recorded by the Late Jurassic-Cretaceous APW path and that predicted by a fixed hotspot model. We believe that this discrepancy reflects uncertainty associated with pre-Late Cretaceous hotspot tracks and poorly constrained relative plate motions during the Cretaceous normal polarity superchron