Bedrock work uncovers new info, ancient faults

Geoscience Prof. John Luczaj is the man responsible for the first comprehensive map of Brown County’s bedrock, part of a statewide project commissioned by the State of Wisconsin and the U.S. Geologic Survey.

The resultant map should be of value to citizens concerned about bacterial contamination in shallow wells; to those who mine crushed stone; and to land-use planners considering aquifer issues, groundwater recharge, and the potential for water and pollutants to travel comparatively quickly through fractured bedrock.

“There are a number of people who need to know about the subsurface: People who are putting in utilities like water pipelines or gas pipelines, they need to know how deep it is to bedrock. People who are operating quarries, they want to know where resources are. People who are trying to figure our groundwater resources and how groundwater contaminates might move. If you don’t understand the subsurface geology you’re not going to have a handle on what those groundwater characteristics look like, how the groundwater is going to move,” Luczaj says.

Luczaj (pronounced LOOCH-eye) and his team inspected outcrops and quarries, core samples from drilling, and well-construction reports. His grant also allowed for a visit by a heavy-duty, earth-shaking “vibra” truck — perhaps the first seismic testing of its kind in Wisconsin, Luczaj says.

The in-ground sonogram helped confirm the existence of long-suspected faults — no longer active and likely millions of years old — in the sedimentary rock that underlies much of Brown County.

Despite roughly 100 feet of vertical displacement, the plates are entirely stable and of direct interest only to groundwater researchers… and, indirectly, to Packers fans, as a curiosity. One of the faults, several hundred feet deep, is believed to run in the general vicinity of Lambeau Field.

Luczaj’s research team included geologists and GIS/database specialists, as well as UW-Green Bay students. The project, more than two years in the making, was supported by $250,000 in grants from the US. Geologic Survey and the UW-Extension state survey, known as the Wisconsin Geological and Natural History Survey.

Luczaj joined the UW-Green Bay faculty in 2005. He was previously a senior scientist and data manager with American Hydrogeology Corp. He holds a Ph.D. and master’s in geology from Johns Hopkins University in addition to a master’s from the University of Kansas and a bachelor’s from UW-Oshkosh.

His mapping project began in the eastern half of Brown County, where relatively less was known about the stratigraphy of sedimentary rocks that are up to nearly 1,500 feet thick in places, and where few wells are deep enough to approach the pre-Cambrian “basement.” The second-year investigation centered mainly on western parts of the county.

A simple version of Luczaj’s Brown County map can be found online.

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