The Kickapoo valley lies in a region known as the Driftless area. This region of approximately 15,000 square miles, including parts of Minnesota, Illinois and Iowa, was missed by the last glacial advance during the Pleistocene era. The topography of the region is characterized by hills and valleys, and is believed to represent the topography of a pre-glacial Wisconsin.
Bedrock in the area consists of shallow marine sedimentary rocks of Cambrian and Ordovician age. The rock at the valley bottom primarily consists of sandstones, along with occasional beds of limestone and shale. These Cambrian layers include the Wonewoc and the Tunnel City Formations.
The Prairie du Chien group, consisting of Ordovician dolomite with minor amounts of sandstone and shale, is found towards the ridgetops. These layers are noted by the presence of rock quarries along several area roads. The St. Peter Sandstone overlies the Prairie du Chien group. Limited exposure can be found in the Viroqua and Westby areas.
An excellent resource for Wisconsin geology, the Roadside Geology of Wisconsin (Dott & Attig, 2004), is available through The Wisconsin Geological and Natural History Survey.