Jo Daviess County Sinkholes

<div><b>Please see the individual layer below to access the detailed metadata.</b><br /></div><div>In order to support science-based water resource management, a systematic effort was undertaken to characterize the nature and function of the hydrogeology in Jo Daviess County, Illinois (County), which is a karst area. Karst is a geologically and hydrologically integrated or interconnected and self-organizing network of landforms and subsurface large-scale, secondary porosity created by a combination of fractured carbonate bedrock, the movement of water into and through the rock body as part of the hydrologic cycle, and physical and chemical weathering (Panno, S.V. et al, 2017). Springs, cover-collapse sinkholes, crevices, and caves are among the defining features of a karst terrain. Examples of all these features are found within the County and have been characterized by scientists at the Illinois State Geological and Water Surveys, Divisions of the Prairie Research Institute, University of Illinois at Urbana-Champaign. </div><div>Cover-collapse sinkholes within the County are developed in thin, fine-grained sediments above three bedrock formations: Ordovician-age Galena Dolomite and Maquoketa Shale, and Silurian-age dolomite. Sinkholes developed within the Galena Dolomite and Silurian dolomite form over crevices that can be as wide as 1 meter (m). Sinkholes developed within sediment overlying Galena Dolomite are typically the smallest ranging from about 1 m in diameter and less than 1 m deep to 5 m in diameter and less than 2 m deep. Sinkholes within sediment overlying Maquoketa Shale are much larger and include collapse of the shale as well. Maquoketa Shale hosted sinkholes are most often found in areas adjacent to the Apple River in the eastern part of the County where the water table has been lowered by discharge to the river. These sinkholes can be 8 m in diameter and 6 m deep, and are unique in that both soil and shale are collapsing into crevices within the underlying Galena Dolomite. Sinkholes within sediment overlying Silurian-age dolomite are typically the largest and can be up to 10 m wide and 7 m deep. These sinkholes typically form en echelon that follow the alignments of meter-wide linear crevices within the underlying dolomite. </div><div>Panno, S.V., Donald E. Luman, and Dennis R. Kolata. Characterization of karst terrain and regional tectonics using remotely sensed data in Jo Daviess County, Illinois. Circular 589, Illinois State Geological Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, 2015. https://www.isgs.illinois.edu/maps/county-maps/karst-terrain/jo-daviess</div><div>Panno, S.V., Philip G. Millhouse, Randy W. Nyboer, Daryl Watson, Walton R. Kelly, Lisa M. Anderson, Curtis C. Albert, and Donald E. Luman. Guide to the Geology, Hydrogeology, History, Archaeology, and Biotic Ecology of the Driftless area of Northwestern Illinois, Jo Daviess County.Illinois State Geological Survey Guidebook 42, 2016. https://www.isgs.illinois.edu/publications/gb042</div><div>Panno, S.V., Donald E. Luman, Walton R. Kelly, Timothy H. Larson, and Stephen J. Taylor. Karst of the Driftless Area of Jo Daviess County, Illinois. Circular 586, Illinois State Geological Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, 2017. https://isgs.illinois.edu/maps/county-maps/karst-terrain/jo-daviess-0</div>