At the posted coordinates you will be at the head waters of an artificial creek in the harbor area. Along the creek are metal plaques embedded in the ground. Search the plaques for clues to the final at :
N39 16.96Y W84 23.44V
Find a plaque with a giant dragonfly.
It's wingspan is 29 2V inches
"Going further back 2Y0 to 280 millions years...."
You are looking for a small lock-n-lock behind a maple on the lake side of the tree