Wooster Geologist in Southwestern Utah (April 2018)

April 21st, 2018

St. George, Utah — I visited southwestern Utah for a week to prepare for an Independent Study expedition next month to study the Carmel Formation (Middle Jurassic). I wanted to update locality information I had collected in the 1990s (ancient times!), find different sections, and meet new people. It was much fun and very productive. The daily blog entries are linked below —

April 16: A Wooster Geologist returns to the Jurassic of southwestern Utah
April 17: Another geological scouting day in southwestern Utah
April 18: Another day in the shallow Jurassic seas of southwestern Utah
April 19: Delightful fossils in the Middle Jurassic Carmel Formation on my last field day

Next month we will have posts from the project!

New article: Paleoecology of an Upper Ordovician submarine cave-dwelling bryozoan fauna and its exposed equivalents in northern Kentucky, USA

April 20th, 2018

I’m happy to link to an article on Ordovician bryozoans that has just appeared in the Journal of Paleontology:

Paleoecology of an Upper Ordovician submarine cave-dwelling bryozoan fauna and its exposed equivalents in northern Kentucky, USA

It is work Caroline Buttler (Head of Palaeontology at the National Museum Wales, Cardiff) and I pursued as our first joint project. An early version is described in this blog post. Thank you to Caroline for her leadership, and the Luce Fund at The College of Wooster for its support. If you want a pdf of the paper, just send me an email note.

[I just noticed this is my 1000th post on this blog!]

Delightful fossils in the Middle Jurassic Carmel Formation on my last field day

April 19th, 2018

St. George, Utah — Today I met Jerry Harris, Professor of Geology at Dixie State University in St. George. He was very friendly, generous and knowledgeable, guiding me to two fantastic Carmel outcrops I would not have approached on my own. Shown above is one complete section of the Carmel Formation in the Dammeron Valley. The reddish rocks in the lower right are the underlying Temple Cap Formation; the top of the ridge is the end of the Carmel here — it is unconformably overlain by the Iron Springs Formation (Upper Cretaceous). This is an extensive exposure perfect for exploring.

The red unit here in the Dammeron section is the top of the Temple Cap Formation. I’m not sure if the Carmel commences with the green marls, but classic Carmel limestone is found immediately above.

A curious unit within the lower few meters of the Carmel is this bedded gypsum deposit. It represents a significant accumulation of evaporite minerals, and thus the evaporation of a lot of seawater in an enclosed basin.

The Carmel limestones show normal (but restricted) seawater and lots of evidence of high energy. These carbonate crossbeds are almost herringbone.

This is a view west from the top of the Dammeron Valley section. In the distant left you can see the familiar Square Top Mountain and pointy Jackson Peak. On the right is the majestic Veyo Volcano. The Gunlock exposures are just a few kilometers away, but no outcrops connect them to the Dammeron Valley.

Jerry Harris also showed me large exposures of the Carmel Formation in Diamond Valley, a few kilometers south of the Dammeron Valley location. It is not picturesque, but there is plenty of Carmel under that sagebrush. The excavation for that water tower turned out to be especially good for shelly fossils, so Jerry took me there right way.

The most common fossil is the pectenid bivalve Camptonectes. It has calcitic valves, so they are well preserved, unlike the numerous aragonite-shelled mollusks in the Carmel that are seen only as ghostly molds.

To my delight, some of the bivalves at this locality are encrusted by small cyclostome bryozoan colonies. Jurassic bryozoans are very rare in North America. In fact, Paul Taylor and I have described most of them from the Carmel! (Taylor, P.D. and Wilson, M.A. 1999. Middle Jurassic bryozoans from the Carmel Formation of southwestern Utah. Journal of Paleontology 73: 816-830.) The exquisite bryozoan colonies above are as good as any we’ve found before. A thorough study of all the Carmel sclerobionts is worth pursuing.

There are also nice wedge-shaped limid bivalves at the water tank exposure in Diamond Valley.

These fossiliferous slabs have lots of treasures. I only wish they were more common in the Carmel.

Here’s a simple Google Maps image of my three main areas of study north of St. George. 1 = Gunlock, 2 = Dammeron Valley, 3 = Diamond Valley. Curiously, the most fossiliferous part of the Carmel Formation (the upper unit of the Co-op Creek Limestone Member) differs significantly between Gunlock on the west and the two valleys on the east, even though they are only a few kilometers apart. The Gunlock area has oyster balls and hardgrounds, which are absent in the east. The trace fossils are also more abundant and diverse in Gunlock than in the other two sections. Shelly fossils, though, appear to be more common in the east. It will be fun to sort out these facies differences in more detail.

Finally, I wanted to include an image of the cinder cone and lava flows at the entrance to Diamond Valley. They are within Snow Canyon State Park and have been dated at an astonishingly young age of 32,000 years.

Great day, great scouting trip. Thanks again to Jerry Harris and Andrew Milner!

Another day in the shallow Jurassic seas of southwestern Utah

April 18th, 2018

St. George, Utah — Back to the Gunlock region for me to revisit old Carmel Formation research sites to check for access issues and new exposures. This trip has also given me a chance to update my images of the unit. Most of my previous images are shockingly on film. I’ve been in this business a long time.

Above is one of my favorite Carmel outcrops, the cliff at Eagle Mountain. The white and buff layers are the Co-op Creek Limestone Member of the Carmel Formation (Middle Jurassic). They are topped by a thick, well-cemented conglomeratic sandstone, The Iron Springs Formation (Upper Cretaceous). This is a nice example of an erosional disconformity between the units with an interval of time unrecorded (a hiatus). The cliff is on private land, so I’m in the process of finding the owners. The image was taken looking northeast from: 37°18.428’N, 113°44.408’W.

Today I looked at some smaller details in the Carmel sections. I found these exquisite mudcracks near the Eagle Mountain locality. This is solid rock, even though the cracks look modern. This shows, of course, that this patch of muddy seafloor dried out, producing the cracks by desiccation of clay minerals.

On top of the mudcracked layer is a thin carbonate bed with vugs and cracks filled with gypsum. This represents a hypersaline environment where gypsum and/or anhydrite was precipitated as evaporite minerals. We thus went in time from a dry seabed to one covered by shallow briny water.

Within the gypsum-rich layers are intraclasts of carbonate mud derived from the mudcracked layer below. When the seawater returned it had enough energy at times to rip up pieces of the hardened mud below.

Finally, on top of the gypsiferous layer is a limestone rich in star-shaped crinoid debris (ossicles of Isocrinus nicoletti). This represents the influx of normal marine water, albeit in a restricted context. As far as I can tell, there are multiple triplet layer sets like this near the middle of the Carmel in the Gunlock area. What was controlling these changes in sealevel and chemistry?

I would be neglecting my duties as a geologist if I didn’t mention that there is much more to the geology here than the Carmel Formation. Above we see the underlying Navajo Sandstone with its massive cross-bedded eolian dune features. The Navajo is topped here by thick basaltic lava flows of Pleistocene-Holocene age (the Santa Clara Volcanic Field).

Lovely place for a geologist!

Another geological scouting day in southwestern Utah

April 17th, 2018

Kanab, Utah — My day began with a visit to the St. George Dinosaur Discovery Site at Johnson Farm, where I met Andrew R.C. Milner, the Site Paleontologist and Curator. This museum is built over an extraordinary set of dinosaur trackways. These tracks were not even discovered when I started working in the area, and now this building houses a busy and productive center for vertebrate paleontology in the region.

Andrew is a dinosaur paleontologist and an expert on vertebrate trace fossils, and he also knows a lot about the Carmel Formation and its outcrops in Utah. He gave me local contacts, and will join us in the field when we start the official Utah Jurassic expedition next month. He has been very helpful.

I then drove to Mt. Carmel Junction on the eastern side of Zion National Park, about two hours from St. George. It is a small place with a surprisingly long Wikipedia page. It sits in the center of several extensive exposures of the Carmel Formation, including this cross-bedded unit made almost entirely of crinoid ossicles. These rocks are called encrinites. This particular Middle Jurassic encrinite is one of the youngest known. This exposure is at Stop #5 of Tang (1997). It is still easily accessible at the northwest corner of the junction.

Alas, this great expanse of Carmel Formation, known as Stop #6 in Tang (1997) is no longer accessible, at least not easily. If you look carefully you can see a barbed-wire fence at the base of the outcrop. I could find no evidence of who owns this land, and jumping a fence out here can have serious consequences! Unfortunately there are far more such fences here than were present in the easy-going 1990’s. This makes taking students here harder for casual examinations of the rocks.

I spent the night in nearby Kanab, Utah, where I got to spend excellent time with my Father, who was in the area hiking with two friends. I then drove back to St. George the next morning, passing through a long stretch of northern Arizona. This included driving by the storied Colorado City of FLDS fame. Follow those links if you don’t know the story!

A Wooster Geologist returns to the Jurassic of southwestern Utah

April 16th, 2018

St. George, Utah — This week I’m exploring the wonderful Middle Jurassic Carmel Formation exposed in southwestern Utah. It is a rare bit of solo fieldwork I’m doing to prepare for a Wooster Independent Study expedition here with students and Nick Wiesenberg in about a month. My colleagues, students and I last did research here almost two decades ago, so I wanted to make sure I knew how access and exposures have changed. Better to explore early than be surprised while leading a team! (One new thing in the above image: a lake where I used to wade across the Santa Clara River to get to the Carmel outcrops.)

The Carmel Formation is 100 to 300 meters thick, more or less, through parts of southern Utah. It is relatively thin by Utah Jurassic standards. It is a mostly marine unit, having been deposited in a narrow restricted seaway. I’ve long been fascinated by its fossils, which are almost entirely mollusks and traces of arthropods. It is time to revisit these exposures with new eyes and ideas.

This is a view looking north across typical Carmel Formation outcrops about a half-hour northwest of St. George. The rocks are exposed in strike valleys, which are great for finding bedding plane slabs with fossils and sedimentary features, but miserable for constructing stratigraphic columns. Luckily most of that tedious work is done. In the background are two iconic mountains for the area: Square Top and Jackson Peak. In April 1983, a B-52 bomber tragically crashed into Square Top.

The Carmel Formation is capped unconformably in this region by the Upper Cretaceous Iron Springs Formation, a conglomeratic sanadstone here. It is cemented well, capping the less resistant Carmel limestones and claystones below. This is a typical strike valley exposure of the top of the Carmel.

This is a Google Maps view of today’s field area, which is in the middle of the image stretching diagonally from the reservoir in the southeast (right) to where the dirt road bifurcates in the northwest.

One of the interesting features of the Carmel is a widespread carbonate hardground. Tim Palmer and I published on it a long time ago, but there are still many questions about its formation and the variety of borings on its surface. Above are two fragments found loose in a wadi.

The Carmel has beautiful sedimentary structures, like the ripples on the left, and cool trace fossils like the arthropod trackway (Gyrochorte) on the right.

I’m intrigued with the dominant oysters in the Carmel: Liostrea strigilecula. They formed “oyster balls” (ostreoliths) almost unique to the Carmel, and these large masses of unknown origin and significance. They seem to be small reef-like forms, but also show signs of occasional overturning. They hosted encrusting bryozoans and boring bivalves.

An early morning view of my field area. The reddish unit below is the Temple Cap Formation, with the base of the Carmel white turning into, shall we say, carmel-colored. The water is part of the Gunlock Reservoir.

Today I sorted out access to a few old localities, and found some new ones. Much has changed here in the last 20 years. There are new roads in and around the growing cities of St. George and Santa Clara, the Santa Clara river has been further managed with massive earthen works (in response to frequent flash floods, no doubt), and there seem to be new barbed-wire fences across some Carmel exposures. Nevertheless it felt like old times as I tramped across the gravelly hillsides scanning the ground for geological treasures.

I must add as a footnote an image of this ugly-but-simple bridge over the Santa Clara River at Miner’s Canyon. For years my students, colleagues and I waded through the river here because the water was too deep for our rental vehicles. This meant we had lots of walking to do once we were on the other side, including walking back loaded with rock samples. Now we can just drive across. I have a feeling, though, that this bridge will not survive the next flash flood!

A Wooster Paleontologist visits the Smithsonian’s National Museum of Natural History

April 5th, 2018

Washington, DC — I have the privilege this semester of being on a research leave from teaching, so I thought I’d report on one of my activities. Without classroom responsibilities I can travel for research opportunities, especially now as the weather in the northeastern US marginally improves. (Despite the sunny view above, it was freezing!)

I visited the Paleobiology Department of the National Museum of Natural History in Washington to examine some particular fossils in the collections, and give a departmental seminar. This is typical for paleontological research, and I’m grateful to the generations of museum scientists who make it possible.

The Collections Manager at the NMNH Paleobiology Department is our own Kathy Hollis (’03). She does such a fine job she’s on a poster board in front of the museum, and she was featured in an excellent Wooster Magazine article on museum science.

Kathy sets me up deep in the fossil collections, endless rows of cabinets. The Paleobiology Department, in fact, has more than 10,000 of these, each with multiple drawers of treasures.

My work is pretty simple at this stage. I find fossils of interest in the collections (most of which I’ve identified from publications) and photograph them for future reference. I use this copy stand, which is the best in the business. (I want one, Department Chair.) The paper tray is filled with lead shot which is useful for positioning specimens at any angle under the camera.

Here’s an example specimen: the ambonychid bivalve Claudeonychia from the Upper Ordovician of the Cincinnatian region. The scale is in centimeters. The dark color is actually an encrusting bryozoan, a story I’ll tell later.

I meet many cool fossils along the way, including this magnificent specimen of Wilsonoceras from Wyoming. It is a nautiloid cephalopod I’ve always wanted to see purely for its name!

Here is the poster for my presentation to the Paleobiology Department. It is a tradition for visiting researchers to present a talk on their work.

This is the Cooper Room where the talks are held. I love its Old School ambiance, and the paleontological history it represents. It is a superb place to present ideas to colleagues in the discipline.

The field season is about to begin for Wooster Earth Scientists, so expect more posts. Again, it is a privilege to have such opportunities.

A geological and archaeological hike in northeastern Ohio on the last day of winter

March 19th, 2018

It was a beautiful latest-winter day in Wooster. Nick Wiesenberg had the great idea of taking an afternoon to hike through Pee Wee Hollow, a wooded area of ravines, streams and rocky exposures a few miles northwest of Wooster near the village of Congress. Greg Wiles, his faithful dog Arrow, and I went along. We had an excellent time with no agenda but to explore. Above is Dr. Wiles standing at an outcrop of Lower Carboniferous sandstones, shales and conglomerates making up the Logan Formation. The rocks are similar to those exposed in Spangler Park.

Pee Wee Hollow has three small Native American mounds on an upper plateau. Nick and Arrow are standing on one above. They were excavated in the 1950s, and possibly pillaged long before that. Dr. Nick Kardulias, Dr. Wiles and several others wrote a paper on these mounds. I can quote the abstract entirely: “While a great deal is known about the many earthworks of central and southern Ohio, there is a gap in our data about such features in the northern part of the state. The present report is an effort to bring work on one such site in Wayne County into the literature. The Pee Wee Hollow Mound group consists of three small circular earthen structures and a possible fortification trench on a high bluff overlooking the main stream that drains the county. Systematic excavation by avocational archaeologists in the 1950s revealed the structure of the mounds and retrieved a small assemblage of artifacts, some charcoal, and pockets of red ochre. Recent analysis of the artifacts, coupled with radiocarbon dating, indicates that the site was a location of some local importance from the Late Archaic through the Middle to Late Woodland periods.” (Pennsylvania Archaeologist 84(1):62-75; 2014)

Another of the mounds with Greg and Arrow for scale.
The very fine sandstones of the Logan Formation are especially well exposed in the creek beds. Here are a set of joints our structural geologist Dr. Shelley Judge would appreciate.

There are even some nice Bigfoot field structures. Who knew?We spent most of our time walking up Shade Creek. The creek bed is mostly Logan Formation sandstones.

Greg is standing here on a bedding planes of sandstone with nice ancient ripple marks. Note, by the way, the chunk of ice above his head. Still winter, but not for long.

Here’s a closer view of those ripples.Arrow here contemplates a thick exposure of dark gray shale. Greg found some nice crinoid columns in it, and I found several molds of bivalves.

The more resistant units in the Logan have the best fossils. This slab of very fine sandstone cemented with iron carbonates (a type of siderite concretion) has several internal molds of brachiopods and white calcitic crinoid columns. I described the remarkable preservation of similar crinoids in an earlier series of blog posts.

A nice, uncomplicated walk in a beautiful bit of nature.

Wooster’s Fossil of the Week: Echinoid bite marks from the Upper Cretaceous of southwestern France

November 30th, 2017

Above is another beautiful image from Paul Taylor’s paleontological lab at the Natural History Museum, London. It is one of our fossil oysters (Pycnodonte vesicularis) from the French Type Campanian collected in the town of Archiac in southwestern France on our most enjoyable expedition this past summer. The fine crossing short grooves are bite marks produced by grazing regular echinoids (sea urchins). They form the trace fossil Gnathichnus pentax Bromley, 1975. You can learn more about this type of fossil in a previous blog entry describing Cretaceous Gnathichnus from southern Israel.

This is a good time to update our readers on the French Campanian sclerobiont project. Macy Conrad (’17) has done extraordinary work identifying the hundreds of encrusting bryozoans on our oysters. She is using a series of mugshots of Campanian bryozoans produced by our colleague Paul Taylor to name our specimens as accurately as possible. All the pink you see in these trays represents bryozoans that have been identified.

Here is a closer view. Very distinct patterns of diversification of bryozoans and trace fossils upward through the stratigraphic column are emerging. Macy will continue this work next semester as she finishes her Independent Study thesis. I will be doing my parts as well, but from a bit of a distance: I’ll be on a research leave next semester.

Which leads me to this announcement: Wooster’s Fossil of the Week will no longer be weekly. Since I’ll have other writing goals and travel plans over the next several months during my leave, I will contribute blog entries less frequently. The name “Fossil of the Week” has become a bit of a brand, so I’ll keep it, just no longer post every week (which I’ve been doing since January 2, 2011).

 

 

Wooster’s Fossils of the Week: Barnacle borings from the Cretaceous of southwestern France

November 24th, 2017

Small comma-shaped trace fossils this week in a Cretaceous (Upper Campanian) oyster (Pycnodonte vesicularis) from the Aubeterre Formation of southwestern France. (Locality C/W-747, Plage des Nonnes, to be exact.) These are borings produced by barnacles, which are sedentary crustaceans more typically found in multi-plated shells of their own making. We’ve seen this fine type of boring before in this blog, so some of this information is repeated.

These boring barnacles (yes, I know the joke) are still around today, so we know quite a bit about their biology. (More on how in a minute.) These acrothoracican barnacles drill into shells head-down and then kick their legs up through the opening to filter seawater for food. They’ve been doing it since the Devonian (Seilacher, 1969; Lambers and Boekschoten, 1986).

This particular trace fossil is Rogerella elliptica Codez & Saint-Seine, 1958. It is part of a diverse set of borings collected on our wonderful field trip this past summer to the Bordeaux region with Paul Taylor.

We know so much about boring barnacles because Charles Darwin himself took an almost obsessive interest in them early in his scientific career. While on his famous voyage on the HMS Beagle, Darwin noticed small holes in a conch shell, and he dug out from one of them a curious little animal shown in the diagram below.

Cryptophialus Darwin, 1854

He called it “Mr. Arthrobalanus” in his zoological notes. He figured out early that it was a barnacle, but he was astonished at how different it was from others of its kind. He later gave it a scientific name (Cryptophialus Darwin, 1854) and took on the problem of barnacle systematics and ecology. Eight years and four volumes later his young son would ask one of his friends, “Where does your father do his barnacles?” The diversity of barnacles played a large role in Darwin’s intellectual development and, consequently, his revolutionary ideas about evolution (Deutsch, 2009).

Burrowing barnacle diagram from an 1876 issue of Popular Science Monthly.

References:

Codez, J. and Saint-Seine, R. de. 1958. Révision des cirripedes acrothoracique fossiles. Bull. Soc. géol. France 7: 699-719.

Darwin, C.R. 1854. Living Cirripedia, The Balanidae, (or sessile cirripedes); the Verrucidae. Vol. 2. London: The Ray Society.

Deutsch, J.S. 2009. Darwin and the cirripedes: Insights and dreadful blunders. Integrative Zoology 4: 316–322.

Lambers, P. and Boekschoten, G.J. 1986. On fossil and recent borings produced by acrothoracic cirripeds. Geologie en Mijnbouw 65: 257–268.

Seilacher, A. 1969. Paleoecology of boring barnacles. American Zoologist 9: 705–719

 

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