north end of the canyon, at Mann Gulch and further north, alternating ridges and valleys reflect the alternating resistance of younger rock layers overlying the Madison Limestone. The entire canyon is an example of a superposed or antecedent stream, in which the river pre-dates the uplift of the rocks and kept pace with erosion as uplift occurred. References External links Wilderness areas of Montana Canyons and gorges of Montana Helena National Forest Protected areas of Lewis and Clark County, Montana Protected areas established in 1964 1964 establishments in Montana