Active Tectonsm In Western North America Three major episodes of orogenies-mountain building-occured along the western margin of North America during the Mesozoic.The oldest orogeny was characterized by a tremendous number of igneous intrusions.Large bodies of granite called batholiths exist throughout the cordillera.The next orogeny was characterized by low-angle thrust faulting and folding.This was caused by a collisional tectonism along the western margin of North America.This type of deformation began in the Late Jurassic and continued through the Late Cretacious.The thrust faults run north-south and place older rocks on top of younger rocks in Utah,Wyoming,western Cananda,and Montana.The third Mesozioc orogenic event was characterized by vertical uplifts.This orogeny mainly affected the area east of the folds and faults caused by the second orogeny.Deformation caused by the third orogeny began during the Late Cretacious and continued into the Cenozoic.