The name game . . .
The Belt Supergroup is named after the Belt Mountains where the rocks were first identified. The Belt Mountains are named after the town of Belt, located about 20 miles southeast of Great Falls . . . and the town of Belt is named after a horizontal exposure of rocks on the side of a hill overlooking the town (above photo). The rocks on the side of the hill resemble a belt worn by "husky" man. The town of Belt sits in a valley to the left of the hill.

Below: This photo was taken along I-15 north of Helena, another place to see interesting exposures of Belt rocks.. The red color of these Belt rocks exposed in this roadcut suggest that they are made of sediment deposited in shallow water where oxygen from the atmosphere was available to combine with iron in the sediments.