I wanted to check it out before wrapping up my bird field season. My friend Sze Wing Yu, a graduate student studying how bison affect streamside vegetation, surveyed the area last year and saw a lot of baculites — extinct, Cretaceous-era sea creatures that look like uncoiled nautiluses with long, tapered shells. These baculite fossils are pretty common, and they are great markers for areas of soil that might be rich in other fossilized, ancient sea creatures.
When I arrived at the creek, I quickly realized that the bulk of the baculites occurred within ironstone concretions, which are basically balls of hard rock within lots of crumbly mudstone. I broke apart three or four concretions using a nearby granite boulder as an anvil and was picking through shards of rock when I noticed one piece with a pattern too uniform to be normal rock. It was covered in mud, but underneath I thought I could see regular, raised bands about 5 inches long — a possible fossil. I threw it in my backpack and continued the hunt.