They form.d in old alluvium from Cretaceous shales and quartzites and argillite rocks. Annual snowfall ranges from 50 to 150 inches. These are the Adel , Gelkie , Pinedale, Pishkun , and Redchief series. Adel soils have mollic epipedons more than 16 inches thick and lack argillic horizons. Gelkie soils lack calcic horizons.
Pinedale soils have sandy-skeletal substrata.
Pishkun soils have ochric epipedons in loamy-skeletal profiles. Redchief soils have more than 35 percent coarse fragments in the control section. Native grasses are western wheatgrass, bluebunch wheatgrass, rough fescue and Idaho fescue. The Michelson series is moderately extensive. Michelson soils were formerly classified as Chernozems.