The greatest amount of relief occurs along the Mississippi River, where relief is up to 600 ft. In the east, loess lies directly on bedrock. Paleozoic sedimentary rocks crop out in valley walls, but are generally mantled with colluvium or loess. 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 is exposed in river and stream valleys.
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. The subsection has a continental climate.