This area used to be under the sea, quite a while back. The salt domes trap oil, which Michigan has a little of. A water well driller mentioned that all the wells he drills 7 miles or so west of here are shallow, because if he goes too deep he always hits salt water. That’s been done there a loooong time.
I think that the halites below the Great Lakes are a great deal older than the Gulf of Mexico salt domes. The Great Lakes salt is associated with the Niagara Escarpment, which was formed when very shallow, hypersaline seas evaporated about 400+ million years ago (Silurian?). I think the Gulf coast salt domes are Cretaceous, less than 100 million years.