Wooster Geologists

Our field work is now done, so we had a day of cultural and natural sites. Our morning started with a visit to the Visitor’s Center at the LDS Temple in St. George. There the students learned at least one perspective on the Mormon faith and Mormon history of the area. It was so intense at times I forgot to take photographs!

Afterwards we went to a different kind of temple — a temple of science built over an extraordinary series of Jurassic trackways and sedimentary features. We’ve been coming to the St. George Dinosaur Discovery Site every year since it was established (except for one wretched covid summer). We met our friend Andrew Milner, who is the curator and a spectacular guide to the fossils.

Vicky is here demonstrating how the famous swimming dinosaur tracks were made. (Yes, we were the only people there with masks.)

Andrew took us into the fossil preparatory lab. One of the highlights was watching a live scorpion (wrangled here by arachnidologist Zach Valois) make tracks in sand which could later be compared to fossil equivalents. With Zach holding the stinger, we were each able to pat the scorpion (a unique experience for me, at least).

After lunch we visited our friends Judy and Jay Leavitt in Gunlock, had more pie in Veyo, and then had a brief hike in Snow Canyon State Park. (Image by Nick.)

Nick also took this picture of what appears to be a hike with maintenance of strict social distancing!

Finally the Wooster flag moment with Vicky and Lucie. A kind of graduation event to mark the successful completion of their first geological field work. They were wonderful field colleagues with sharp observations, strong work ethics, and tolerance for gnats and rattlesnakes!

This morning the Wooster Geologists visited the westernmost exposure of the lower Carmel Formation at Nielson’s (1990) Jackson Peak section. Nick and Vicky are shown above on the road towards the conical Jackson Peak in the background. The site was as buggy as any other on this trip, with not a breath of wind to relieve us.

Nick took this image of our team hiking up a wadi in search of a good place to make a stratigraphic column. Jackson Peak looms in the background.

We established the base of the section in a wadi at N 37.327356°, W 113.858144°. Because of the rough terrain, the gnats, and the mostly-covered nature of the stratigraphy here, we decided to use Nielson’s (1990) original measurements and then sample along his column. Note that burned trees give very little shade.

Another image by Nick of Wooster Geologists at work. In the background is Square Top Mountain, which is most notable as the site of a B-52G crash in 1983.

This is the highest in-place outcropping of the typical lower Carmel Formation stromatolitic micrite beds. You can see the fine microbial layering on the weathered surfaces of the rock. Sampled as JP-1.

Like an old friend, the distinctive sandstone we saw in the Manganese Wash section showed up here at Jackson Peak. It has the same weathering appearance and, at the handlens level, the same lithological composition. Sampled as JP-2.

Unlike at the Manganese Wash section, the sandstone at Jackson Peak has an ooid shoal biosparite/grainstone directly above it, our sample JP-3.

This ooid shoal deposit as the same low-angle cross-bedding and current ripple marks as we’ve seen in all our Carmel Formation sections.

At the top of the ridge we were studying, Lucie and Vicky came across our second rattlesnake of the trip. It buzzed immediately, so Lucie and Vicky moved away quickly. Nick got this great image.

On our way back from the Jackson Peak section we met two Bureau of Land Management officers on horseback. Now there’s a cool job. (Photo by Nick.)

As is our tradition on these southwestern Utah expeditions, after we finished our work at Jackson Peak, we visited the 1857 Mountain Meadows Massacre site a few miles to the north.

This is the cairn marking the mass grave of 34 of the victims buried on the massacre site. It is a sad and enraging story we encourage you to read at the link above.

Today Team Utah 2022 climbed the outcrops in Dammeron Valley, north of St. George, to collect trace fossils from the Co-op Creek Limestone Member of the Carmel Formation (Middle Jurassic). It was a bit of a slog up the rubbly talus cones that provided passage over the cliffs, but the trace fossils up there were worth it. Beautiful day, but our friends the gnats lurked in the shadows. Thanks to Nick for the image.

The very base of the section is the gypsum-bearing red claystone and siltstone Temple Cap Formation, shown here with Lucie for scale.

About midway up the slope, just above the highest stromatolitic unit, abundant trace fossils appear. Vicky is ready to collect!

The trace-bearing outcrop is not very photogenic, but those brown slabs on the surface have numerous ichnofossils. Location: N 37.276667°, W 113.640350°.

The red marker shows our study site in Dammeron Valley. Note it is just above the boundary between the whitish lower part and brown upper part of the member.

I was particularly interested in these funnel-shaped traces (the circular pits), which were abundant, along with the familiar Gyrochorte. We haven’t seen these elsewhere in the Carmel Formation in SW Utah.

This slab shows a thick mass of Planolites trace fossils. Each stripe on the Jacob’s Staff is 10 cm.

And that was it for the day. Later we’ll report here on what we found after our lab analyses back in Wooster.

Many veterans of the Wooster Geology expeditions to southwestern Utah will remember the insatiable, abundant, nearly overwhelming biting gnats that occasionally proliferated during our fieldwork. We’ve suffered them each day, but this was the worst experience thus far, mainly because we were collecting data in a nearly windless wadi at their mercy. (Image by Nick.)

But first, our day began with another section for Lucie’s Independent Study project, this one on the Eagle Mountain Ranch at N 37.307688°, W 113.739697°. Above is a ghostly, pensive Lucie in the shadows waiting to scramble up from the base of her section. It is again a stromatolitic sequence, this time with desiccation cracks and a top layer of calcitized gypsum nodules. Above this we eventually reached the lower oolitic shoal deposits of the upper unit. It all went as planned, with critical stratigraphic measurements (and structural observations) from Nick and Shlley.

After lunch was our descent into Buggy Gulch, otherwise known as the Manganese Wash section we measured, sampled and described on Sunday (N 37.283125°; W 113.803696). Beautiful day for us and, unfortunately, the clouds of gnats. We were stuck in place measuring current ripples and cross-bedding in the main oolitic shoal deposits. Shelley showed us how to do the work with her mad structural geology skills. We collected a boatload of data at the expense of our sanity. I’m scratching bites as I write this.

Bug complaints aside, the sedimentary structures here are well developed. Here is a set of current ripples with easily-measured crests and clear directional indicators.

The cross-sections through the shoals display complex cross-bedding, the product of multiple changes in current directions and velocities. This is important data for our paleoenvironmental reconstructions.

Finally, we’ll end the day with a gorgeous prickly pear cactus flower, suitably crawling with insects.

One of my favorite Jurassic outcrops in all the world is found on the Eagle Mountain Ranch north of Gunlock, Utah (locality C/W-142; EMR). It has an exposure of the Carmel Formation with the perfect orientation to produce fossils weathered out of the matrix, yet not dissolved. We met the new owners of the ranch, Layne and Betsy Bangerter, who could not have been more friendly and accommodating. It was also a beautiful, cool day. Nick took the above image during lunch.

The main task we had today was collect trace fossil data and specimens for Vicky’s Senior Independent Study project. The star was the common Gyrochorte, of course.

This large trace fossil, with its two lobes of curved spreiten (essentially internal laminae) confuses me. I’ll have to spend some time thinking about it before hazarding an identification.

We found a couple of these odd gouges along bedding planes. I like to think they represent ichthyosaurs running their snouts through the sediment. (I have zero evidence for this interpretation.)

We found many other fossils as well, including a rare coral (good work, Lucie) and nicely-bored bivalves.

Tomorrow we return and dig (literally) into the lower part of the member for Lucie’s project. Here we see it nicely exposed along a cutbank of the Santa Clara River. (The water level is so low we can’t see it from here.)