Ordered a couple books yesterday on Michigan mines and native copper, planning to detect some native copper this summer...
I don't know what it's like on your side of the state , but stuff is buried deep here near waterways. Spring sediment distributions ect..
Forested areas have the accumulated loam from centuries of leaves.
One site I've left alone is downstream of some mounds.
There are mounds farther downstream , none of which were burial type.
(Yes , we;re getting away from copper culture . but maybe the woodland cultures found the same sites as good camps? Or had relics from earlier times?)
Anyways...An old Sioux now passed on to a camp in the sky (yes ,a Sioux in Mi.) used to poke around downstream of the upper mounds and found relics eroded out and tumbled downstream.
You have a source of lithic material near the Sag. bay that saw travel ,and material relayed away from.
Maybe the copper from further NorthWest found an intersection /route through your area.
Some writings confuse the goins ons. I don't want to insult the authors who mention a cache relay system ,or routes copper followed ,or who "mined" copper....
But I'll hold that copper found mobility through hand to hand for a very long ways.
Finding thin historic layers of loam or erosion might help.
I've not found copper relics , but a couple small pieces of suspected float copper.
An "Uncle" recovered copper knives. He's gone now so I can't ask the hows and whys of the site , but it was long attended by earlier people.
It was lake and small stream related. Not unlike another area not far from it (an easy days warm season travel) where a "pickle" field turned up lots of relics when first turned.
What that field looked like thousands of years ago we didn't know. But the water was far enough away that humans camped near it would not bother (by detection) that field area.
Dad always wanted to search around two giant white pines near. For some reason suspecting relics near them.
Never heard of him detecting it. And unlikely just walking it would reveal anything sighted.
One of a few sites now out of reach...With varied stories associated.
Good researching is wished to you on your interest into the copper culture. It ranged far...