Karst and shallow carbonate bedrock in Wisconsin Wisconsin Geological and Natural History Survey Factsheet 02 | 2009 Areas with carbonate bedrock within 50 feet of the land surface are particularly vulnerable to groundwater contamination.
NORTH 0 20 40 miles
0 20 40 kilometers
DOUGLAS BAYFIELD
ASHLAND IRON VILAS
BURNETT FLORENCE WASHBURN SAWYER MARINETTE ONEIDA
PRICE LANGLADE FOREST RUSK POLK BARRON DUNN LINCOLN TAYLOR MENOMINEE
ST. CROIX CHIPPEWA OCONTO PIERCE
MARATHON SHAWANO DOOR PEPIN EAU CLAIRE BUFFALO OUTAGAMIE UNEE CLARK A KEW WOOD PORTAGE WAUPACA BROWN JACKSON ADAMS WAUSHARA WINNEBAGO MANITOWOC TREMPEALEAU
LA CROSSE ALUMET
MARQUETTE GREEN C LAKE SHEBOYGAN MONROE VERNON JUNEAU FOND DU LAC
RICHLAND WASH-
CARBONATE BEDROCK INGTON UKEE CRAWFORD (in depth below surface) COLUMBIA OZA DODGE 0–50 feet SAUK GRANT JEFFERSON WAUKESHA
> 50 feet KEE
WAU IL
DANE M IOWA
RACINE
LAFAYETTE GREEN ROCK WALWORTH KENOSHA
Wisconsin Geological and Natural History Survey 3817 Mineral Point Road • Madison, Wisconsin 53705-5100 Tel 608.263.7389 • Fax 608.262.8086 • WisconsinGeologicalSurvey.org Director and State Geologist: James M. Robertson Karst and shallow carbonate bedrock in Wisconsin
Wisconsin Geological and Natural History Survey Factsheet 02 | 2009
Carbonate aquifers are exception- Types of questions to ask: ally vulnerable to contamination n Is carbonate bedrock present in for two reasons: the subsurface? n Groundwater flow in fractured n How deeply is it buried? In other rocks and karst systems can be Fracturing and bedding in an exposure of words, what is the thickness of extremely rapid—tens to hun- carbonate bedrock near Sturgeon Bay in the overlying material? Door County. dreds of feet per day. n What is the nature of the over n Carbonate rocks are poor at lying material? For example, Carbonate bedrock, rock for- filtering or otherwise removing what is its origin, composition, mations composed primarily of contaminants. limestone or dolomite, underlie grain size, etc? the southern third of Wisconsin in Some site-specific questions to Water- and land-use management a V-shaped belt (see map on other ask about carbonate aquifers plans in areas with carbonate bed- side). These rocks are commonly rock should always address these fractured, with the fractures provid- Carbonate aquifers are particu- sorts of questions as they seek to ing primary pathways for ground- larly vulnerable where overlying protect groundwater quantity and water movement. soils are thin or absent. There are quality. numerous examples of ground- Carbonate rocks are soluble, and water contamination of carbon- percolating surface water can For more information, contact ate aquifers in such settings in Kenneth R. Bradbury, Ph.D. enlarge fractures to form conduits, Wisconsin. Consequently, land-use Wisconsin Geological and caves, and sinkholes that are the activities in areas of carbonate Natural History Survey hallmarks of a karst system and its 608.263.7921, [email protected] rock must be carefully managed to related karst landscape. avoid the release of contaminants In Wisconsin, karst landscapes are to groundwater. direct evidence of underlying shal- low, fractured carbonate bedrock. But the lack of classic karst features Typical features of a karst sytem and landscape: in a landscape does not mean Seepages, sinkholes, caves, fractures, springs, and stream sinks. that shallow fractured carbon- ate bedrock is absent, or that the groundwater is potentially any less vulnerable to contamination. Carbonate bedrock and groundwater contamination Carbonate formations are impor- tant aquifers in Wisconsin. These aquifers supply water for homes, farms, cities, industries, and other human uses as well as maintaining water levels in lakes and wetlands and flows in streams and springs. Runkel and others, 2003