Sinkholes and landuse in southwestern Wisconsin

The karst developed in the Ordovician carbonates of southwestern Wisconsin contains several hundred sinkholes, in response to which landowners have adopted landuse strategies to minimize personal inconvenience and risk. Of 263 field-documented sinkholes, 75% are formed in the Oneonta Formation dolostones of the Prairie du Chien Group, and the remaining 25% are in the Platteville and Galena dolostones of the Sinnipee Group. Sinkhole densities are generally low, but often individuals are clustered on the tops and sides of interfluvial ridges between dry valleys. Although contemporary dissolution rates are low, sinkholes are currently forming at a rate of 5 to 10 per year. Most sinkholes are small, but locally they are a significant hazard to livestock and farm machinery. Contemporary landowner response includes avoidance, fencing and infilling. During the nineteenth century some sinkholes, particularly on the Platteville and Galena dolostones, were mined in search of lead ores.