Mt. Yamnuska is one of the most recognizable thrust faults in the Rocky Mountains. The McConnel thrust that formed Mt. Yamnuska occurred during plate convergence, causing reversed stratigraphic succession as the older Cambrian layer was thrust on top of the younger Cretaceous layer. This is an erosional unconformity missing around 150 million years of sediment deposits. The Cambrian layer of rock seen in A-1 forming the cliff edge is composed of Eldon formation limestone. This limestone came from a marine environment, specifically the shallow sea that once covered most of Western Canada. Belly River formation sandstones and dispersed beds of coal and shale comprise the lower Cretaceous layer. This sandstone was deposited as a delta that surrounded the sea that covered central North America during the Late Cretaceous. The shale and coal beds are from swaps and estuaries that were present along the delta, like seen in image B-1.