Chiefly maps.; "This project was funded by the Great Lakes Geologic Mapping Coalition surficial mapping grant program"--Page iv.; Includes bibliographical references (page 6).; "A digital elevation model (DEM), generated from LiDAR data, was used to create a map layer that identified low, enclosed areas. To locate potential sinkholes, these low spots were cross referenced with known karst points from previous studies, bedrock geology, aerial photography of multiple sources and ages, soil maps, glacial drift thickness maps, and water well logs. ... Suspected karst features were then visited in the field, evaluated, and photographed. Through this process some of the LiDAR-derived depressions were found not to be sinkholes; features such as building foundations, broken field tiles, steep-walled streams, road culverts, and glacial features often produced enclosed areas similar in shape to sinkholes. Springs do not typically show up as depressions unless a catch basin was built and subsequently failed, thus many were located during field work by spotting springhouses. Field visits are important for confirming sinkhole sizes and depths as well. ..."--Page 2.; Harvested from the web on 12/22/1
