Researchers expanding geologic atlases to inform counties, land and well owners

16 sediment cores hold clues to available water resources in three counties

MINNEAPOLIS / ST. PAUL (05/12/2026) — Roughly four million Minnesotans get their drinking water from wells or groundwater held in natural aquifers. Researchers at the University of Minnesota Twin Cities recently collected 16 sediment cores that hold clues to available water resources in three counties. 

The findings, by the Minnesota Geological Survey (MGS) within the University's School of Earth and Environmental Sciences, will result in new geologic atlases for Koochiching, Freeborn and Cottonwood counties. 

The County Geologic Atlas Series is an ongoing coordinated effort between MGS and the Minnesota Department of Natural Resources (DNR). It consists of an updated water-well database with geologic interpretations and 1:100,000-scale geologic maps showing the properties and distribution of sediments and rocks in the subsurface. The MGS contribution — considered the “container” — is followed by the DNR contribution, which maps water movement and water quality by aquifer. Together, the two parts form a complete County Geologic Atlas.

Currently, atlases are complete or underway for 81 of the 87 counties in Minnesota.

“By combining fieldwork with laboratory analyses, we create accurate, data-driven maps that support the sustainable management of our groundwater and geologic resources,” said Dr. Robert Tipping, director of the Minnesota Geological Survey.

Drilling for sediment cores is among the first steps in the multi-year atlas production. The work to compile and analyze data on Koochiching, Freeborn and Cottonwood counties will run through 2029.

“Each core is like a time machine, providing glimpses into past events both as we see it today, and as it appeared over many tens of thousands of years ago,” said Jordan Van Berkel. 

Van Berkel, a glacial scientist at the Minnesota Geological Survey, is one of the authors on the Atlas series who helped coordinate the core drilling. 

“These core samples help define the geometry and chemistry of both buried aquifers and aquifers well-connected to the land surface,” he explained. “They reveal what these areas were like before, during and after glaciers covered most of Minnesota.”

In coming months, the researchers will continue to interpret and map the subsurface using data from drill core, field observations, geochronologic age-dating tools and geophysical equipment at the Minnesota Geological Survey lab in St. Paul. 

“Our maps have a practical aspect regarding groundwater quantity and quality,” said Tipping.

“Glacial clays, which include lake sediment from historic lakes, commonly cap the top of an aquifer,” Tipping added. “If you are a private well owner, knowing what’s on top of your aquifer — what the “roof” is made of and its thickness — is important. That tells you how widespread your water resource is, how well-connected it is to the land surface.”

The research was funded by the U.S. Geological Survey Great Lakes Geologic Mapping Coalition, the Minnesota Environmental and Natural Resources Trust Fund and the Minnesota Clean Water, Land and Legacy Amendment.

The Minnesota Geological Survey—County Geologic Atlas Series is available online for public viewing on the University of Minnesota Digital Conservancy website. 

Atlases and reports are also available for purchase at the Minnesota Geological Survey office.