Named for occurrences within valley of Monument Creek, U.S. Air Force Academy site, El Paso Co, CO in the Denver basin. These occurrences are designated the type locality. Found also along most of the streams flowing into Monument Creek and Kettle Creek. Lithologic content varies with drainage basin. Where derived from older gravels consists predominantly of unconsolidated interbedded fine gravel, sand, gravelly and sandy silt in layers 6 in to 6 ft thick, and silty clay in layers 4 in to 1 ft thick. Maximum dimension of pebbles is 1 in. Along Monument Creek where granitic material available, consists predominantly of sand and gravel, and has boulders and cobbles of granite. Two measured sections described. Is younger than Kettle Alluvium (new) and older than Husted Alluvium (new). Correlated with Broadway Alluvium of Denver area. Of Pleistocene, or late Wisconsin age. Geologic map.

Source: GNU records (USGS DDS-6; Denver GNULEX).