The Grantfork series consists of very deep, somewhat poorly drained soils formed in loamy materials and the underlying glacial till, or entirely in till, on sideslopes of the Illinoian till plain. These soils contain a concentration of exchangeable sodium in the subsoil.
Permeability is slow.
Slope gradients range from 2 to 20 percent. Grantfork silty clay loam - on a severely eroded slope of 9 percent in a field of clover at an elevation of about 590 feet above mean sea level. 38 degrees 59 minutes 42 seconds N. and long. The depth to the base of the argillic horizon is 45 to 80 inches or more. The till commonly is at depths of 30 to 40 inches, but is as deep as 45 inches in some pedons and is at the surface in others.