Stromatolites; WAY cool! We will see a lot of these on our geology tour tomorrow to Ahern Pass. FYI - there are living stromatolites off of Australia. As to this specimen, there is an article about it that I found online: https://epod.usra.edu/blog/2017/05/stro ... -park.html
The park is made almost entirely of rocks from the Belt Formation (also known as the Belt Supergroup) - layer upon layer of sandstones, shales and carbonates from the late Precambrian Era. At that time, there were no organisms with bones or shells, so stromatolites are the only fossils that can be found in Glacier Park. Fossils of different species of stromatolites can be found in different areas of the park.