fossiliferous adj. bearing or containing fossils; "fossiliferous strata"
I can think of no better way to describe the area I got to explore today with the director of the Bryce Canyon Natural History Association (the park's bookstore). Though we were outside of the park on private land, the Tropic Shale is one of the oldest sedimentary layers exposed within Bryce, and it is home to lots of fossils. The Tropic Shale are marine sediments that represent the period when the Western Interior Seaway (also called the Mid-Cretaceous Seaway) was at its greatest extent during the Cretaceous Period.
Mostly a dark gray dirt, I learned that you look around for "concretions" of limestone exposed as the dirt is carried down the hillside - this is where you look for fossils. These first 2 images are ammonites: cephalopods related to modern squids and octopi. The first is one with a coiled outer shell, the second with a slightly curved shell. Sometimes you find them just lying on the ground, sometimes they are embedded in the rocks. In the case of this second ammonite, I first found a rock containing the fossil's impression, then found the fossil itself after several minutes looking around in the rubble. An interesting fact about ammonites is that they are never found above the K-T Boundary: they became extinct at the same time as the dinosaurs 65 million years ago. The first measures about 5.25 cm (2 in.), the second 3.75 cm (1.5 in.).
Unfortunately I don't remember any of the exact names of the fossils I collected today (I have over 20 pounds of rocks and individual fossils), I'll be be getting all of that once I've had a chance to clean and sort. This is
some kind of shellfish a Turritella species, a gastropod family that arose in the Cretaceous and still around today, measuring 3.2 cm (1.3 in.), very well preserved and still attached to the rock on one side. The rock that underlies the Tropic Shale is called the Dakota Formation and, across the highway from where we were working, radiometric dating determined the Dakota to be 93 million years old, making these fossils younger than that, but older than 65 million years. To me that is just amazing!
This is a small collection of some other examples; the three at the top are Pycnodonte sp., a type of extinct oyster. The first (left to right) is the outside top portion of the shell, the middle shows the inside of another shell, the one on the the right is the bottom part of a shell. The Pycnodonte are just everywhere - in one spot where I was standing there were thousands just lying there on the ground. These measure roughly 2.75 cm. (1.5 in.) On the bottom row we have another ammonite (4.25 cm., 1.75 in), a small clam (also 2.75 cm., 1.5 in.) and a gastropod - in this case a small marine snail type creature (2.5 cm., 1 in.).
All in all, it was a very interesting day (in the next few days I'll try to get the names and, when I do, I'll update the post).