This shows an eroded section of the tropic shale formation. Look closely and you can see at least 3 horizontal layers containing a scattering of boulders. These are places where sea levels remained stable long enough for more solid rocks to form.

It is in those more solid horizontal layers where invertebrate fossils can be found.

Much of the tropic shale is grey colored and consists of large amounts of loose volcanic ash that you can easily dig into with your hands. However, the fossils are found in solid rock concretions that must be broken open to reveal the fossil within.