The Emigrant Springs Formation was designated by Kellogg (1963) for exposures in Sec. 8, T. 9 N., R. 62 E. , in the southern Egan Range.

The Emigrant Springs Formation is Late Cambrian in age. It overlies the Patterson Pass Shale and conformably underlies the Dunderberg Shale at its type locality in the southern Egan Range.

The Emigrant Springs Formation is composed of thin-bedded silty or oolitic limestone, and massive gray limestone and highly deformed varicolored mudstone with a basal intraformational limestone conglomerate. Fossils include echinoderm and crinoid debris, and agnostid trilobites (Kellogg, 1963).

A stratigraphically equivalent section in the northern Schell Creek Range was designated as Hamburg Dolomite by Dechert (1967) or Raiff Limestone (Young, 1960) and is here described as the Emigrant Springs Formation. The formation consists of a lower 1,100 feet of dark gray to black, fine to medium-grained, thick-bedded to massive limestone which is locally silty and dolomitic in the upper portion of the unit (Dechert, 1967). This is overlain by an upper unit of about 1,380 feet of dark gray dolomitic limestone, thin-bedded silty limestone, and oolitic limestone with rare dark chert nodules and lenses. The upper beds are commonly light blue-gray medium-grained, platy and silty limestone (Dechert, 1967).

The Emigrant Springs Formation is 2,064 to 2,232 feet thick at its type locality in the southern Egan Range (Kellogg, 1963), and 2,540 feet in the northern Schell Creek Range (Dechert, 1967).

The Emigrant Springs Formation is exposed in the southern Egan Range and is present in the Schell Creek, Fairview and Bristol Ranges where it is not differentiated from other Late Cambrian units.

The presence of intraformational conglomerates, echinoid and crinoid debris, suggest that the Emigrant Springs Formation represents shallow marine shelf sedimentation.