Herald JournalHerald Journal, Oct. 18, 2004

Waverly considered ‘geologically unique’

By Ryan Gueningsman

More than 60 geologists from eight states and Canada arrived in Waverly Oct. 8 to explore glacial deposits from past ice ages.

They were in town to attend a continuing education course “Improving the Description and Characterization of Glacial Successions for Environmental and Engineering Projects” conducted by the Midwest GeoSciences Group and the University of Minnesota.

Directed by Dan Kelleher from Waverly and Tim Kemmis from Sheboygan, Wisc., the group has been conducting these types of courses since 1996.

Waverly (actually south-central Wright County) is unique geologically because two continental ice sheets (glaciers) collided and moved southward side-by-side during an early ice age (called the early Wisconsinan Age) in this area, according to Kelleher. Each ice sheet deposited distinctly different sediments.

The western ice sheet is referred to as the Wadena Lobe and it deposited gray clay-like sediment, whereas the eastern ice sheet, referred to as the Superior Lobe, deposited red sandy sediment. The Minnesota Geological Survey did not know the precise boundary where these lobe collided and moved together.

The most interesting geologic fact discovered in the 115-foot deep boring was the evidence of two separate ice advances during the most recent ice age.

The most recent sediments were deposited during the Late Wisconsinan Age from an ice sheet called the Des Moines Lobe (named after the city located at the end of the ice movement).

This is the first confirmation of two Des Moines Lobe advances in Minnesota, although this is well verified in Iowa. Nonetheless, Kelleher considered this finding “awesome.”

“The goal of the course is to help practicing hydrogeologists and geotechnical engineers unravel the complexities of glacial deposits and improve our understanding of the local geology,” Kelleher said. He is a hydrogeologist and one of the five course instructors.

The Minnesota Geological Survey explained the glacial history of Minnesota, focusing on Wright County.

“Geologic information from the drilling will provide new insight to past glacial episodes and will be used to revise the state-wide geologic model,” said Harvey Thorleifson, the director of the Minnesota Geological Survey.

The morning classroom sessions summarized the principles of glacial depositional environments and provided a geologic model based on research by the Minnesota Geological Survey.

The afternoon outdoor sessions featured a newly developed drilling method called “Sonic Drilling” by Boart Longyear from Little Falls. Dr. Paul Kesich from Fermi National Accelerator Laboratory stated that sonic drilling is changing the drilling industry, due to large and dependable core samples.

In addition, American Engineering Testing from St. Paul was on-site to update procedures using its new cone penetrometer testing tools.

The drilling rig was one of only 21 of its kind in North America. The new drilling technology is called sonic where the core barrel is advanced using a high-frequency vibration, instead of the traditional water circulation. Boart Longyear Company from Little Falls (the rig was from Cape Cod, Mass.) conducted the drilling, and American Engineering Testing from St. Paul used its cone penetration testing rig to drill 50 feet on two different locations in the yard.

The instructors indicated that the courses are gaining popularity due to their practical nature. The courses are planned on a year-to-year basis and pictures can be seen at www.midwestgeo.com.

“We had a great time doing this course and it was an overwhelming success, based on the feedback from the attendees,” Kelleher said.

Another interesting observation is that deep boring confirmed the sediments comprising the hill south of Waverly are derived from a retreating ice margin.

“In other words, a block of the retreating ice sheet stagnated in the location of present-day Waverly,” Kelleher said. “Slow-melting ice blocks eventually left depressions, forming the present-day lakes, and the sediments cascading from the ancient ice formed the hills surrounding the lakes. This is the landscape model used by the Minnesota Geological Survey which was confirmed and verified by our boring.”


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