Correlation of plate motions with continental tectonics: Laramide to basin‐range

Some of the major tectonic and magmatic events of the last 150 Ma in the Western Cordillera can be correlated with a new model for the displacement histories between western North America and adjacent oceanic plates. Sierra Nevada plutonism ended and Laramide compression began during increasingly rapid convergence of the Farallon plate with North America and during a moderate increase in the westward motion of North America in the hotspot reference frame. The end of the Laramide and beginning of widespread arc magmatism and extension correlates with slowing of both of these motions. The spectacular slowing of Faralion‐North America convergence is attributed to the decreasing age of the Farallon plate entering the trench and thus to a change from negative to positive buoyancy. The transition from widespread arc‐related magmatism and rapid extension to basaltic volcanism and moderate extension in the Basin and Range province finds no ready explanation in the plate motions of the Pacific basin. A change to oblique spreading in the Basin and Range province accompanied growth in length of the San Andreas fault as the Mendocino triple junction progressed northward.