Some areas of rock were exposed by rain and sun each causing snow to melt in small areas on this site. Lots of fossils were exposed, including this one, which may be a Nautiloid. These fossils may be around 200million+ years old. I should have mentioned when I posted all the other fossil photos, that the site where they are found is on the edge of a huge quarry. Enormous quantities of rock have been blasted away, exposing things buried for millenia, such as these fossils.