Just think back 20,000 years and you will find some spots. Really!
There is an old wildcat gravel pit/dump on the end of my road along a river that was a bank on a branch of the Ausable about 5000BC when the Lake Huron shoreline was almost at West Branch. In the 60's I dug some out and panned it. I got a few specs of flour gold every few pans. Figured 60 - 80 hours would give about 1/2 a gram. If you get lucky you may find a pocket.
The Ausable used to be a delta of branches that spread from alpena to standish. All the smaller rivers around it now in that area were branches. What are now hills between them were sandbars, islands and high banks on a ripping river system from melting glacers sitting above the roscommon area. Same thing happened to the west, Manistee, Pere Marquete and the Muskegon where pretty much channels then branches of 1 super river.
Most college libraries have reference geo books that map the river systems and lake shores back to the glacier age. For instance when your on I-75 in north Bay County or the thumb you see these sand ridges/treelines in the fields, some being used as sand pits, that were shoreline sanddunes 250 - 500 years ago. Some have been plowed under and are just a sandy smear in the middle of the field. We used to hunt them for arrowheads when I was a teen.
If you look north of the smiley face water tower when passing west branch you will see a huge sand bluff on the north horizon that was a monster shoreline sand dune, comparable to sleeping bear dunes.
There is a guy on ebay that sells bags of panning concentrate from the UP gold area starting at $10.00. You can pick your river but he may be out until spring. Never tried his stuff but until recently it looked almost cheaper that driving there.
