Fossil Butte National Monument: a geology nerd heaven: Cokeville to Kemmerer
Monday June 24, 2013, 38 miles (61 km) – Total so far: 2,263 miles (3,642 km)
There is not much to Cokeville. There is a diner that’s for sale, two motels, one truck stop, one out-of-business truck stop, a post office and a school. A man bombed the school in 1986, and that may have been the last event of any consequence to occur in this town. It is pretty dead.
The road south out of town is federal highway 30, so there are a decent amount of trucks on the road. They are all moving way over for me this very early morning, though, as I head down the Bear River Valley. Thanks, guys!
The valley is long, and fairly flat. The river lazily winds it way through the flats to the west. You can see the road ahead rise and fall far into the distance as it hugs the edge of the valley. I keep trying to see where the road heads east, thinking there will be a climb in that to get over the row of hills that the road has been paralleling since leaving Cokeville. As a sidenote, we are also paralleling the Crawford thrust fault here. It is the westernmost major overthrust in the state.
Eventually, the road does curve east, but there is no climb. The road zigs and zags through these overthrust hills as it follows a creek. Not only is there no climbing, really, but it is mostly downhill. The wind is funneling west though, so I’ve got a stiff headwind to battle. Down in the depths of the canyon, I gaze up at the rounded hills above me. There are no trees here, just grass, sagebrush and other bushes able to survive in a semi-arid climate. The Oregon Trail follows through this canyon; there are markers denoting its trace. It all feels quite desolate and lonely. The high hills above the road look like they could just swallow a person whole. We ride across another overthrust fault, a small one called the Tunp fault. The high, rounded hills are the Tunp Range – the fault trace can be seen in one of the roadcuts. Very cool. Don’t ask how long I stood there looking at that one!
The canyon finally deposits me into an open, semi-arid basin surround by high ridges of sagebrush. Just before the end of the canyon, the county road that runs in front of the national monument turns off from Hwy 30. It is unpaved, but I should have taken that one instead of following official signs. It would have been much quicker. Instead I ride three miles or so east on Hwy 30 then have to back track those 3 miles on the paved portion of the county road. Ah well.
I have been anticipating my visit here for nearly two years. This site was one of the first additions to my initial route planning back in early 2011. I have seen fossil fish from this area in rock shops for as long as I’ve been going in rock shops. So I’m excited to finally go see the “Kemmerer fish”.
I slowly climb the hill to the visitor centre. I look off to the famous butte, going over the formation names, ages and deposition sequence in my head. I try to remember the story that goes with this place. I must have read it a dozen times over the past two years. I also think about the time scales of Earth’s history as I follow the interpretive signs up the hill. Can you hear the clink as the leash is unclipped – Nerd Em is on the loose!
The diversity and detail found in the fossils here is phenomenal! The beauty and the abundance just blows my little brain. There is even a crocodile behind the information desk. I am so in awe – I just can’t get enough. My poor Mom just sorta follows me around, marveling at me marveling at all these intricately detailed plant and animals so perfectly preserved. While fish by far show the greatest abundance and variety here (over 20 species), the monument also has the oldest complete bats in the world, snakes, turtles, birds, many plants and more.
About 50 million years ago, this part of Wyoming was covered by three lakes – Lake Gosiute, Lake Uinta and the lake found here – Fossil Lake. In a warm and subtropical climate, the lakes slowly filled with river deposits, chemical precipitates such as trona and layers of oil shale. These deposits are today known as the Green River formation which is 200-300-feet thick. It is the vertical, tan layer in the photo above and where most of the fossils are found. (The Historic Quarry trail also features the pink Wasatch formation – a river deposit where they’ve found many mammal fossils).
My mom and I drive up to the top of the monument on a dirt, switch-backed road. We then hike along an old 4WD track to the edge of the butte, overlooking the famous formation here at the monument and in the distant hills. We can also look west to the hills of the overthrust belt. It is very windy up here, but my mom is gracious and allows me all the time I want to stand up here and try to imagine this as a small, subtropical lake teeming with life (in and out of the water) 50-55 million years ago. I also imagine being here 150 million years ago, looking west to the overthrust belt, knowing the ocean lies not too far beyond. It is all such a contrast to the dry, cool and high semi-arid landscape of today!
After a picnic lunch at the Chicken Creek trail, we go off to do the Historic Quarry trail. If you visit this monument, make sure you do this trail. The trail climbs Fossil Butte to the Green River formation to a quarry that was worked in the 1960s. Exhibits all along the track give a great history of the area, how the fossils formed and how to look for them in the rock. Once you get your eye in for finding the red edges in the thin laminates, you will be amazed at just how plentiful these fossils really are. Truly outstanding! My mom, non-nerd and non-geology lover, is very impressed, too, though I think most of the time she’s just worried about being blown off the cliff by the hefty wind.
What an amazing day! I am one happy chick to have finally seen the site where all the fossil fish come from. However, I do feel a sadness as I think about this beauty. Given the extensive deposition of the Green River formation throughout southwestern Wyoming, there is only this one tiny area that is protected. The Green River formation is not only fossil rich, but it is also resource rich. It deeply saddens me to think of all the fossils destroyed all over southwest Wyoming as the trona deposits and oil shale are mined. Oh yes, there are billions of fossils, but I cannot help but think what amazing things we are destroying going after the oil shale. All of that life, all of those beautiful and intricate fossils destroyed… for a hydrocarbon that is associated with significant air quality, waste disposal and water quantity issues in its processing. This afternoon, as I catch a ride to Kemmerer with my mom, my heart feels heavy at the same time that my soul feels whole and connected. Such is life.