“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. The boulder with the markings is 3.5 to 4 feet high and about 5 feet long. Photos show a surface with numerous fissures. Some may be natural while others appear of human origin, but those forming what could be the petroglyph stood out, Holley said.
http://www.record-eagle.com/local/local_story_248101751.html/resources_printstory
http://dsc.discovery.com/news/2007/09/05/mastadon_arc.html?category=archaeology&guid=20070905101500

When mastodons ruled northern Michigan:
http://www.wzzm13.com/news/news_article.aspx?storyid=80355

Rare Find in GT Bay from IPR News Radio
(2007-08-13) John Bailey explains why an ancient rock carving in Grand Traverse Bay could bolster his view of the origins of Native Americans living in the Great Lakes:
http://www.publicbroadcasting.net/wiaa/news.newsmain?action=article&ARTICLE_ID=1129504

From another blog: “This would of course be very cool if true. I previously posted here and here and here on possible Pleistocene rock art and how rare it appears to be…” http://stephenbodio.blogspot.com/search?q=%22Mastodon+petroglyph