The Gibbon series consists of very deep, somewhat poorly drained soils.
Permeability is moderate or moderately slow.
They formed in stratified, calcareous alluvium on flood plains. Slopes range from 0 to 2 percent. Mean annual temperature is 53 degrees F and mean annual precipitation is 23 inches at the type location. Gibbon silty clay loam - with a slope of less than 1 percent, in a cultivated field. The mollic epipedon ranges from 10 to 20 inches in thickness.