 The current southern Rockies were forced upwards through the layers of Pennsylvanian and Permian sedimentary remnants of the Ancestral Rocky Mountains.Such sedimentary remnants were often tilted at steep angles along the flanks of the modern range; they are now visible in many places throughout the Rockies, and are prominently shown along the Dakota Hogback, an early Cretaceous sandstone formation that runs along the eastern flank of the modern Rockies.Immediately after the Laramide orogeny, the Rockies were like Tibet