When Ryan Bernard with his metal detector found a hunk of metal buried 2 feet beneath his backyard last summer, he almost threw it in the trash. Upon further examination, it may be an artifact from a prehistoric culture. Ray Reser, director of the Central Wisconsin Archaeology Center at the University of Wisconsin-Stevens Point (USA), described the object as a copper 'celt,' a type of ax blade with no perforations or grooves. He said the celt was probably a functioning tool. The piece probably dates from 3,000 to 5,000 years ago.
     Similar findings have been made throughout the Upper Midwest, most notably in Oconto, Wis., where a site unearthed in 1952 now known as Copper Culture State Park yielded several burial plots and artifacts. Thomas Pleger, a professor at the University of Wisconsin-Baraboo/Sauk County, wrote his doctoral dissertation on the Old Copper Complex. He described these prehistoric societies as seasonally-mobile people whose temporary homes were based on abundance of particular resources. Hunting, fishing and trade were the basis of their lives. The Old Copper Complex is one of the oldest metal-working societies in the world.
     The copper likely started out in the Keweenaw Peninsula. Bernard believes it could have been 'float' copper, that is, deposited by retreating glaciers. Pleger said it was more likely acquired via trade. Keweenaw copper from this era is easily identifiable because of its exceptional 99 percent purity, making it suitable for forming right out of the ground. Reser said Keweenaw copper artifacts have been found in Mexico, the Rockies and the East Coast. "This stuff was highly coveted. It was intensively traded up and down the Mississippi River valley," he said. For the first thousands of years, most copper artifacts from this culture were used as tools. By 1000 BCE, Pleger said more pristine items, such as jewelry, can be found.
     Pleger said because those people were fairly mobile, and due to the perishable nature of their materials, archaeologists have yet to excavate well-preserved habitation sites connected to the Old Copper Complex, but the nature of their finds does retain some clues. "One of the other nice things about copper artifacts is that it tends to preserve organic material that it comes into contact with," he said. The oxide created in the copper over time retards bacterial growth.
     Metal detecting technology has resulted in many similar finds, but not all people have taken as much care with what they found. "Collectors find these things and will often clean them up, destroying the evidence we can use to date them," Pleger said. Pleger said there are many unknown elements of the Old Copper Complex, but archaeologists, both professional and impromptu, must be smart with what they find. "It's important to understand that the archaeological resources of Michigan, Wisconsin, Canada are non-renewable," he said.

Source: Record-Eagle (9 April 2008)