Wallace Formation  search
BTChronostratigraphic Units
 .Precambrian
 ..Proterozoic
 ...Mesoproterozoic
 ....Wallace Formation
RTIdaho
 Montana
 Belt Supergroup
 Newland Limestone
SNIn Piegan Group of Belt Supergroup. Thin-bedded bluish and greenish more or less calcareous shales, underlain by rapidly alternating thin beds of argillite, calcareous sandstone, and impure limestone. NE Idaho, and W Montana.