The Major series consists of very deep, well drained soils that formed in alluvium from mixed sources.
Major soils are on stream terraces and relict basin floors.
Slopes range from 0 to 5 percent. Major fine sandy loam - rangeland. Driest during May and June. Ustic aridic soil moisture regime. Thought to have formed from calcium and magnesium that precipitated out during fluctuating seasonal water tables under a climate much wetter than the present.