Glaciation of the Michigan River Basin, North Park, Colorado

Evidence was found of four glacial advances in the Michigan River Basin in the southeastern corner of North Park, Colorado. The earliest of these advances (Owl Mountain) is considered to be pre-Wisconsin, probably Illinoian. The three later glacial advances-named Gould, Silver Creek, and American Lakes, respectively-likely represent substages of the Wisconsin. A still later period of more rigorous climate is evidenced by cirque moraines, protalus ramparts, and rock streams found at the head of several of the tributary valleys, some of which were occupied by ice during the American Lakes glaciation. Two terraces, 35-50 feet and 20-25 feet above the Michigan River, can be directly correlated with the Gould and Silver Creek moraines. A still lower indistinct terrace may have been deposited during the American Lakes advance. No terrace can be definitely correlated with the deposits of till of Owl Mountain age.