Sedimentary rocks were deposited in a geosyncline in the Cordilleran region from late Precambrian to Tertiary time. The present tectonic framework of the Rocky Mountain region began to form during the Late Cretaceous and early Tertiary with the development of uplifts and intermontane basins (Laramide orogeny). Volcanic activity was moderately important on the west during the Cretaceous, but igneous intrusion and volcanic activity became widespread throughout the Rockies in the Tertiary.

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