Derrynane soils average greater than 20 percent sand in the lower part of the series control section. Okoboji soils have weaker structure in most or all subhorizons and commonly have carbonates at shallower depths. Wabash and Rantoul soils average greater than 45 percent clay in the particle-size control section. Zook soils have mollic epipedons greater than 36 inches thick. Peotone soils typically are in potholes and depressions on Wisconsinan till plains and have concave or plane surfaces.
Slopes are less than two percent.
These soils formed in colluvial sediments from adjacent or surrounding nearly level or gently undulating soils. These are the Andres , Ashkum , Elliott , and Flanagan soils. The somewhat poorly drained Andres, Elliott, and Flanagan soils are on higher parts of the till plains. The poorly drained Ashkum soils are on adjacent low-lying areas but have mollic epipedons less than 24 inches in thickness. Very poorly drained.