A productive first day for Wooster Geologists in Utah

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.

About Mark Wilson

Mark Wilson is a Professor of Geology at The College of Wooster. He specializes in invertebrate paleontology, carbonate sedimentology, and stratigraphy. He also is an expert on pseudoscience, especially creationism.
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