Named for Monroe Canyon in secs 32 and 33, T7S, R40E, as the upper formation of the Chesterfield Range Group (new name). Type section measured approximately at elevation 6,200 ft on northwest-trending spur in NW1/4 sec 20, T7S, R20E, Bannock Co., ID in the Snake River basin. Is a replacement term for Brazer Limestone. Is a massive-bedded, fine- to medium-grained, brownish-gray to olive-gray, fossiliferous limestone. Is 923 ft thick at the type section where it is divisible into a 408 ft thick massive limestone member, at base, 204 ft thick, medium-bedded limestone member in the middle , and 311 ft thick cherty limestone member at top. Overlies Little Flat Formation (new name); underlies Wells Formation. Contains brachiopods and corals of Meramec and Chester age. Assigned to the Late Mississippian.

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