Complete Bouguer gravity and aeromagnetic maps of the Rattlesnake Roadless Area, Missoula County, Montana

The Rattlesnake Roadless Area was identified by the U.S. Forest Service as a possible addition to the Wilderness System.  This 120 square mile area is north of Missoula, Mont. (see index map); Rattlesnake Creek forms the major drainage to the south.

The rocks in the study area consist mainly of the Helena Formation and the Missoula Group of the Belt Supergroup (Proterozoic Y).  Rock units of less importance are diabase sills and dikes of probable Proterozoic Z age, Middle Cambrian rocks, and glacial deposits.  Structurally, the study area consists of the Rattlesnake thrust system in the south part and a parautochthonous area broken by vertical faults in the north part.