It was a beautiful Saturday, so we decided to take a few friends out to go fossil hunting. We packed a picnic in the cooler, hopped in the car, and set out for Sanpete Valley. I had heard that you could go just about anywhere in the Wasatch Range and find decent fossils, so assumed it would be easy to find something.
We drove south on I-15 and headed off into Spanish Fork Canyon. The scenery there is very beautiful and the geology is quite diverse–the road cuts through multicolored hills high above a scenic valley. We soon came to Thistle Junction and turned off toward Manti.
In 1983 Thistle was the scene of a landslide that forever changed the economy of Utah. The river was damned up, swamping the town and covering the railroad line as well. After months of costly excavation the trains were able to go through again, but many industries in Utah had withered on the vine and the town of Thistle remains partially submerged in water. It’s an interesting spot to take a few pictures.
After Thistle you pass through Birdseye, named after an oolitic limestone called Birdseye Marble. This stone was quarried for many historic buildings around Utah, including the Capital Building. I have heard that although the quarry itself is closed off, it’s possible to collect material on the side of the road heading up the hill to the quarry.
We were on the lookout for fossil beds, but the scenery was fairly monotonous. I was getting a little nervous by the time we passed Fairview. No promising road cuts so far. We knew there had to be something there, so we turned around and backtracked a little. Just north of the turnoff to Milburn, we saw a side road to the west ending in a long, deep excavation in a hill. That had to be as good a place as any, so we got out the shovel and investigated.
The hillside turned out to be a very good fossil bed. We found layers of clay alternating with what looked like half-inch thick shale. It made for very interesting digging. I stuck my chisel in a crack and started pounding away–each hammer blow cracked through another layer of mudstone, and in between each layer there were little black fossils of what appeared to be ostracodes–small sea creatures that looked like seeds. The clay was cool and fairly dry, and the ostracodes seemed preserved instead of fossilized. They were easy to separate from the clay, and crumbled under pressure. We had fun gathering the best ones, sliding down the hill and breaking mudstone like dinner plates. All in all, I think the trip was a success.
I’ve looked online, and I think our specimens are much more attractive that the others I’ve seen. The black of the fossils contrasts nicely with the yellowish-tan clay, and the matrix is easy to trim away. Some of the specimens are isolated, and others are packed together in patterns. I’ll probably go back sometime soon to get more.
I’m intrigued that people spend their lives studying tiny niches of natural science. I didn’t realize that they hold symposiums on ostracodes. Check out this book I saw on Amazon–I guess these little critters have a devoted following…