Glacial till is underlain by Cretaceous marine sedimentary rock. Soils include mesic and frigid Borolls and Ustolls, with poorly drained Aquolls in depressional areas. These soils are generally deep and range in texture from sandy to clayey. Potential Natural Vegetation. The natural prairie vegetation is mainly western wheatgrass, needleandthread, green needlegrass, and blue grama.
Little bluestem is important on sloping and thin soils.
Northern reedgrass, prairie cordgrass, big bluestem, and slim sedge are important species on wet soils. Northern flood plain forest occurs along major drainages. This Section is an important migration corridor for most species of waterfowl, but especially for American coots, snow goose, mallard, and blue-winged teal. Other typical species include greater prairie chicken, great crested flycatcher, eastern phoebe, blue jay, brown thrasher, dickcissel, and orchard oriole. Typical herbivores and carnivores include white-tailed deer, mule deer, and bobcat.