"In a surprisingly under-reported story from 2007, Mark Holley, a professor of underwater archaeology at Northwestern Michigan College, discovered a series of stones – some of them arranged in a circle..."
The find, near Traverse City, includes a stone that may have a prehistoric carving.
"The granite rock has markings that resemble a mastodon - an elephant-like creature that once inhabited parts of North America - with what could be a spear in its side, say divers who have seen it.
It was part of a row of stones of varying sizes that might have marked the shoreline 6,000 to 10,000 years ago, Holley said.
Some - although not the boulder - were arranged in a circle. That could indicate human manipulation although it's unclear, said Rob Houston, a geology instructor at the college who has inspected the site."
Of course, further study and research is needed, but I think this is very interesting and wanted to share it.