Wooster Geologists

Hurricane, Utah — Our expedition had its final official fieldwork today, which we marked with a group photo overlooking the magnificent Snow Canyon. See the end of this post for alternative flag group images!

Tomorrow the group visits Zion National Park. The next day will be spent exploring the local geology and culture, and then it is packing up our samples for shipment to Wooster. Today, though, The Carmel Formation calls one last time!

We returned to the extensive Carmel outcrops in Dammeron Valley, looking at the northernmost extension of the ooid shoal facies. Here is our short shoal section at Dammeron Valley North (DVN), which consists entirely of cross-bedded limestones placed in four subunits (A-D).

This exposure weathered into many loose slabs from the upper subunit D. The trace fossils are well preserved, including this Planolites with rare branching. It is convex hyporelief.

The traces here include a sinuous bilobed Gyrochorte and a thick trace in the left foreground I can’t yet identify. Anna found this rippled slab.

This big trace Evan found is almost certainly Rhizocorallium.

We originally thought that our section today (DVN) was an extension 638 meters to the west of the DV shoal unit. Nick and Shelley did excellent stratigraphic detective work to show that DVN is about 15 meters below the DV measured unit. We thus found the eastern equivalent of DVN at the DV location, measured and sampled it. For now we call it “DVN at DV”. More detail than anyone wants to know, but these blog entries are also a kind of field notes!

The traditional Wooster flag group photo as taken by Shelley.

The flag group photo taken by Nick.

Hurricane, Utah — Today Team Jurassic Utah traveled to Mt. Carmel Junction, east of Zion National Park, to examine the extensive outcrops of the Carmel Formation in the region. The most famous location is in Mt. Carmel Junction itself (MCJ: N 37.22521°, W 112.68095°). It is this crinoid-rich limestone that is reported to be the youngest encrinite in the geological record.

Anna and I measured a two-meter column in this unit to collect samples for thin-section analysis. Four subunits (A-D) start at the bottom of the ruler here.

This is the base of subunit D. It is full of the star-shaped columnals of the crinoid Isocrinus nicoleti. It is one of only three Jurassic crinoid species in North America.

Fieldwork! Love it. Photo by Nick.

Shelley again measured cross-beds to determine current directions here. This was a complicated task because at least three joint sets intersect in these rocks.

Lunch along the Virgin River. Photo by Nick.

After lunch we went just a bit south of Mt. Carmel Junction to examine a Carmel Formation outcrop that looked superficially like it would be identical to the previous unit. We call the place Carmel Cove (CC: N 37.21548°, W 112.68215°). Turns out the limestone here is very different: no crinoids, no ooids, and relatively abundant bivalves. Amazing variability in sections within sight of each other.

Hurricane, Utah — Well, maybe not fully polar, but it was very cold and windy in southern Utah today. Our glove-less fingers were numb, and the bitter gusts penetrated our pitiful parkas. We collected some samples but put off measuring columns (which inevitably requires working fingers) for a warmer day.

Our mission, as before, was to find ooid-rich units for Anna and mollusk fossils for Evan. We were at the “Water Tank” locality (C/W-751) of last year. It is our least attractive site, having a blue water tower and all.

The bivalves here are numerous and diverse, but only in a narrow horizon (so far). They are certainly more species-rich than at yesterday’s Eagle Mountain Ranch site.Anna found a cross-bedded ooid-rich limestone along the road to the water tank. We will be back to measure and sample this section in detail.For lunch we went to nearby Snow Canyon State Park, where we hoped it would be a tad warmer. (It was — barely.) The sun was out and the colors vivid. This is the Petrified Dunes walk. All you see here is the glorious Navajo Sandstone (Jurassic — beneath the Temple Cap and Carmel Formations).I was entranced by the Moqui Marbles, a kind of iron oxide concretion that weathers out of the Navajo Sandstone. They accumulate in large numbers on the flat surfaces here.

Nick with Moqui Marbles eroded out of the Navajo.Here are Moqui Marbles in place in cross-beds of the Navajo. (Guess whose legs are the scale.) These concretions are diagenetic, forming in the sandstone long after deposition. You can read the latest ideas on their formation in this Moqui Marbles article.

The cold, cold group in Snow Canyon. Image by Shelley.

Hurricane, Utah — Team Jurassic Utah 2019 started its fieldwork on a cloudy March day with a bit of a chill and some light rain, but it didn’t rain again and the cooler temperatures were comfortable. We worked on the Eagle Mountain Ranch site (C/W-142) looking for ooids (Anna’s Independent Study project) and mollusks (Evan’s I.S. work). Thank you again to ranch owners Hyrum and Gail Smith for permission to work on this important outcrop. (Photo by Nick Wiesenberg.)

Anna and Evan are here describing a critical meter-thick resistant limestone in an otherwise clay-dominated portion of the Co-Op Creek Limestone Member of the Carmel Formation. We think it represents a normal marine incursion into an otherwise restricted lagoonal environment. This is where most of the fossils and ooids at Location C/W-142 come from.

The base of the unit has these very nice wave ripples indicating shallow water.

Nick and Shelley did excellent work measuring the 39 meters of our Carmel interval. They used a Jacob’s Staff with a Brunton compass attached to account for the rock attitude (strike and dip).

Shelley and Nick are the colored dots at the top of our Eagle Mountain Ranch section. They sampled the top of the Carmel here, finding it to be a brecciated limestone below an unconformity with the overlying Upper Cretaceous Iron Springs Formation. The grey wedge of rock thickening to the left is a mysterious claystone. With the breccia discover, we at least know it is above the Carmel.

The team at lunch overlooking the Eagle Mountain Ranch. The slope seemed much steeper than this! (Photo by Nick.)

I know it doesn’t look like much, but Evan found this internal mold of an ammonite at C/W-142. It is the first I’ve seen in the Carmel. (Later Andrew Milner will show us another ammonite from the same location.)

This is the venter view. Definite ammonite, but unidentifiable beyond this!

On the walk back from our main locality, we examined a laminated micritic part of the Co-Op Creek Limestone Member (Location Strom-mat at N 37.30882°, W 113.73883°). This is just below our main section of interest. (Photo by Nick.)

Anna is photographing close details of this unit.

The laminations are spectacular, apparently representing microbial mats. Another future Independent Study project!

Finally, on our drive back to Hurricane we checked out our access to the classic oyster ball localities on the west side of the Santa Clara River. Here is an image of the bridge last year.

The bridge today! A flood destroyed it last month. No way we’re crossing here. Time to explore other options.

Team Jurassic Utah at the Gunlock Reservoir, with the fantastic Carmel Formation in the background.