Karst Unit Mapping Using Geographic Information System Technology, Mower County, Minnesota, Usa

Mower County is in southeastern Minnesota in the area underlain by the sedimentary bedrock of the Hollandale Embayment. These rocks are Middle Devonian and Middle Ordovician karstic limestone and dolomite. As part of the Minnesota Department of Natural Resources County Geologic Atlas mapping project, the karst features of the county are being inventoried. These features include sinkholes, disappearing streams, caves, dry valleys, and springs. Previous karst mapping efforts for other county atlases in Minnesota have produced sinkhole probability maps and a springshed map, In Mower County, we are trying to develop a new type of karst map using a Geographic Information System to produce a karst unit map. Karst units are discrete three-dimensional bodies in which solution of the bedrock has resulted in the integration of surface water and groundwater. While the field mapping and hydrologic investigations were done with conventional methods, the karst unit delineation was done using a Geographic Information System. Using this technology allowed us to examine the county's karst using two-dimensional and three-dimensional views. Many different overlays of the karst elements were combined to better understand the landscape dynamics. Ultimately, it was the overlay of the karst features, hydrologic information, and depth to bedrock mapping on a shaded relief base map that allowed us to best delineate the individual karst units.