Great lakes region inhabitants: I am looking for a special dig-site of mainly trenches in MI?

I remember once I had gone on a hike a couple of miles at least out to site. This was between 2003 and 05. This area out past many trees had numerous intertwining trenches. In these are fossils of some type of shell. If I remember correctly they were one to three inches across. It has been many years since I have been there and since I have been told no place like that exists near here by anyone I mention it too. I distinctly know that this is a real place yet forget where it was. The place I had lived at at this time was around a south-eastern michigan city. The site was about 60-120 minutes drive away.