Matthew Kuchta pulled on blue laboratory gloves and placed a brittle piece of black and brown charcoal, about the size of a dime, under a microscope. “This probably was a hardwood tree,” he said as he examined the magnified wood fibers.
The tree likely burned sometime after the last Ice Age ended, he said. Then, over the course of the next few thousand years, pieces of the charred wood ended up embedded along what now is a stream bank in the lower Red Cedar River valley.
Kuchta, a physics department professor at University of Wisconsin-Stout, along with a student intern found the charcoal last summer while looking for clues to a natural mystery.
The many chunks of charcoal they dug out were a good start. The samples ranged from 400 to 9,000 years old and helped them begin to see the big picture — the haystack, as Kuchta calls it — of how the river has behaved in recent millennia.
Their goal is to get to the bottom of the lower Red Cedar River’s history, literally and figuratively, and learn valuable lessons from the research.
The Red Cedar River starts in Sawyer County and flows 85 miles before it empties into the Chippewa River northeast of Durand. The watershed drains nearly 1,900 square miles in parts of eight counties, including Dunn County as it passes through Menomonie and near UW-Stout.
Last summer was the initial stage of a research project Kuchta hopes will continue for several years. It is the first geology study of the lower Red Cedar. The geology of other major rivers in the region has been studied, but the lower Red Cedar has been virtually overlooked by scientists for the last 100 years, he said.
This fall, students in Kuchta’s Soil Science class and Conservation and Soil Mechanics class are moving the research forward by further studying the samples collected last summer.
“It isn’t just research for research sake. It goes beyond the classroom and makes a contribution to understanding the environment we’re living in. Maybe we can use this to help identify potential conservation priorities in the future,” Kuchta said.
“We want to tie the Red Cedar River’s past to today. Where is it shoving sediment around now? What is the impact of the last 150 years of agriculture on the river?”
Kuchta will present his study to date, “Fluvial Development of the Lower Red Cedar River Valley,” at the Geological Society of America annual meeting Sunday and Monday, Oct. 9-10, at the Minneapolis Convention Center. His intern, Kate Gurke from Lawrence University in Appleton, also will attend and present a poster at the event. More than 6,000 scientists will be on hand.
“One of the most surprising things we've found this summer is that postglacial erosion in the Red Cedar Valley may have had a strong impact on the (much bigger) Chippewa River. All the sediment being transported from the Red Cedar may have delayed erosion along the Chippewa River upstream in eastern Dunn County by over 1,000 years,” Kuchta said.
“We often think of rivers as fairly simple systems where big changes are needed to control a river's ability to erode or deposit sediment on the floodplain and that bigger rivers just take the water and sediment from their tributaries and move it further downstream. The response of the Red Cedar to past changes was complex. After the Ice Age, relatively small changes in water and sediment supply resulted in large, long-lasting changes to the river's landscape.”
The right tools
Tangible evidence of the summer research resides in what Kuchta affectionately calls the Dirt Lab in Jarvis Hall Science Wing. The lab is filled with buckets of river sediment, glass beakers with cloudy water and scientific tools for studying sediment.
Kuchta and Gurke used:
• Large topographical maps to plot the river’s terraces. Most of UW-Stout’s campus, for example, is on one terrace or floodplain. The university’s Challenge Course, on higher ground to the south on 17th Avenue, is on another terrace that is about 1,000 years older.
Kuchta and Gurke mapped eight river terraces below Menomonie High School. The current riverbed near the city is about 100 feet lower than it was at the end of the last Ice Age about 15,000 years ago, Kuchta said.
• Radiocarbon-dating. Charcoal samples, sent off campus to be dated, helped reveal what was happening to the river and when. “If we get a radiocarbon date from charcoal buried beneath one terrace and a younger date from charcoal buried in a lower terrace, it gives us time brackets for when the river changed,” Kuchta said.
Charcoal samples came from eroding banks and abandoned stream channels along the Red Cedar River and Irving and Galloway creeks. Some charcoal samples were from trees and others from plant matter. “The presence or absence of wood helped determine the timing of an important ecological transition period. Forests yielded to prairies and grasslands,” Gurke said.
• An auger and hydrometer. The auger was used to take soil cores of river sediment. The cores were analyzed with a hydrometer, whereby a sediment sample with sand, silt and clay is suspended in water, revealing the relative proportion of large and small sedimentary particles. Bigger pieces are deposited in fast-moving water and smaller pieces in slow-moving water, helping piece together the river’s history when the samples from different terraces and streams are compared.
Gurke, a senior majoring in geology, came to UW-Stout for the summer as part of a program that matches Lawrence students with alumni at other universities. Kuchta graduated from Lawrence in 1998; he is in his third year teaching at UW-Stout.
Most of the funding for the summer project came from a Faculty Research Initiative grant through Research Services at UW-Stout.
Kuchta wrote his doctoral thesis on the geology of the Upper Mississippi River. “This summer represented a big step forward in understanding the Red Cedar,” Kuchta said.
To see a related video about Kuchta’s study, go to UW-Stout’s YouTube channel at http://www.youtube.com/user/uwstoutvideos.