I was just reading an old geological survery online. The subject was Hubbard County geology. Hubbard county is where I live. It is quite dull, and not referenced even once in my new Minnesota geology book. To begin, there is no exposed bedrock. The line of moraines running east to west may tell a little about the history of the movement of glaciers, to someone who can read the signs. In the southeast corner there are a few pieces of soft, impure limestone, indicating there might be late cambrian era strata underneath the surface.
I suppose one could dig deeper and look into the geochemical interaction between ground and lake water. There are also soil surveys, aerial maps, and charts of bedrock geology. There is also the study of sediment from lakes that were left behind by melted ice glacier.