The northern boundary marks the northern extent of loess deposits. There is also small outwash plain that marks the northern boundary. The western portion is a gently rolling glacial till plain that is covered by loess in places. This subsection consists of level to gently rolling older till plains. Topography is controlled by underlying glacial till along the western edge of the subsection, where loess is several feet thick.
Sinkholes are common in the southwestern portion of the subsection.
Bedrock exposures are common. In general, sediment thickness varies by landscape position. Large exposures of bedrock occur in the steep ravines. Devonian dolomite and limestone are more locally exposed along the western edge of the subsection. Cambrian siltstones, sandstones, and shales influence soil properties.