They are similar enough in composition and elevation to be equivalents of the nonmarine Cretaceous rocks in Minnesota, although no fossils have been found in them. This is the only deposit in Wisconsin between the Paleozoic and the Pleistocene. If there are any dinosaur fossils in Wisconsin, they will probably be here. It's a long shot, but not out of the question that there may be a few fossil fragments. Given the location of the Windrow formation on very high summits, it's pretty unlikely that any Cretaceous rocks might be hidden further east beneath glacial deposits.
Erosion is a fact of life in geology, and when the last outcrop of a unit is eroded away, it's gone.