These soils formed in residuum from weakly consolidated shales or massive clays of Permian Age. The climate is subhumid or moist subhumid. These are the Chickasha , Renfrow , and Zaneis series. Chickasha and Zaneis soils have less than 35 percent clay throughout the solum. Renfrow sils have solums more than 60 inches thick.
Infiltration is rapid when the soil is dry and cracked, but very slow when the soil is moist.
Native vegetation is tall and mid grass prairie. South central Oklahoma and possibly north central Texas. The series is of moderate extent. The Tamford soils were formerly included with the Staoford and Vernon soils and classified in the Grumusol great soil group.