The Canadian Rockies are composed of sedimentary rock, including shale, sandstone, dolomite and limestone. The vast majority of geologic formations in Banff range in age from Precambrian to the Jurassic periods (600–145 m.y.a.). However, rocks as young as the lower Cretaceous (145–66 m.y.a.) can be found near the east entrance and on Cascade Mountain above the Banff townsite. These sedimentary rocks formed at the bottom of shallow seas between 600 and 175 m.y.a. and were pushed east during the Laramide orogeny. Mountain building in Banff National Park ended approximately 55 m.y.a.