In addition, limestone bedrock is at depths of less than 40 inches in Calmar and Rockton soils and greater than 40 inches in Atkinson soils. Durand soils have less sand in the upper part of the B2 horizon which formed in loess that ranges from 15 to 25 inches in thickness. Joslin soils contain more clay in the lower part of the sola which formed in reddish clayey lacustrine deposits. Morrill soils have thinner sola and are underlain by Kansan or Nebraska glacial till that has a low content of illite. Pana soils contain more sand and gravel in the lwer part of the sola, are more acid, and are deeper to free carbonates.
Winnebago soils are moderately to steeply sloping on uplands.
Slopes range from 2 to 30 percent. Winnebago soils formed in layer of Wisconsin age loess less than 15 inches thick, and in exhumed paleosols of Sangamon Age formed in sandy loam drift of Illinoian Age. The fresh glacial drift contains illite as the dominant clay mineral. It is believed that the part of the sola in drift was formed before the loess was deposited and that the climate may have been unlike the modern climate. Mean annual temperature ranges from 45 to 53 degrees F, and mean annual precipitation from 30 to 40 inches.