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The annual Wooster Paleontology field trip to the Upper Ordovician (Fall 2017 version)

September 10th, 2017

It’s not that I haven’t loved all my Invertebrate Paleontology classes, but the students this year are special because there are only ten of them. Lately I’ve had up to thirty students per class which is great for many reasons, but running field trips is not one of them. With ten students we can go places buses can’t, and I can pay closer attention to what each student is experiencing. Today’s field trip to an exposure of the Upper Ordovician upper Whitewater Formation near Richmond, Indiana, was delightful. (C/W-148; N 39.78722°, W 84.90166° — which has a nice Google Maps street view.)

The stratigraphy here is very simple and well delineated by generations of geologists. All the students need to do is collect fossils. They don’t know much about them yet because the course has just started, so their collections will be the basis of ongoing preservation and identification projects. Here we see Meredith Bruch and Victoria Race (below) finding goodies, while Fox Meyer climbs up the talus pursuing fabulous fossils.

Our geological technician Nick Wiesenberg went along as a driver and an ace fossil collector with an excellent eye, which I learned about when he helped Team Minnesota last year.

Ann Wilkinson enjoys the wonders of roadside geology in the Midwest.

Here’s a nice representative slab Fox collected of the fossils at this location. Brachiopods, bryozoans, and bivalves dominate the fauna.

Every student had a tray awaiting him or her on return to Wooster.

And the students did their work. Now each needs two trays. They will begin this week washing, labeling and sorting their specimens. Then they start identifying, using among other sources the excellent Digital Atlas of Ordovician Life and Cincinnatian Strata websites.

As a bonus, below is part of the 2007 Invertebrate Paleontology class on the same outcrop. Some alumni may recognize themselves, even though they are in classical paleontological poses.

Wooster’s Fossil of the Week: A rudist clam from the Upper Cretaceous of southwestern France

September 8th, 2017

When we picked up this beautiful fossil in southwestern France this summer, Paul Taylor immediately predicted it would become a Wooster Fossil of the Week. Macy Conrad (’18), Paul and I were on our wonderful expedition in the Type Campanian (Upper Cretaceous) of France. Paul took us to a most unpromising plowed field, claiming there were fossils here from the Maurens Formation. Sure enough we found a pile of large fossils that farmers had picked from their fields. They included probably the most distinctive invertebrate organism of the Late Cretaceous: the rudist clam. Hard to believe these conical objects were clams, but such is evolution. (They have the disconcerting shape and size of other objects found in some French fields: artillery shells!)

The cone itself is the right valve of these sedentary bivalves. The capping valve is the left, as seen here from the top. (Right and left make little sense unless you think of their more traditional bivalved ancestors.) Note that this valve has a reticulate, almost lacy pattern to the shell. Rudists were filter-feeders like most bivalves, but they may have also supplemented their nutrition with photosynthetic symbionts in their mantle tissue. The holes in the top valve may have allowed sunlight to hit the upper mantle.

This stratigraphic chart, courtesy of Platel et al. (1999) via Paul Taylor, shows the Maurens Formation at the top of the Campanian in southwestern France. Our primary Campanian work in SW France is with the three units below (the Biron, Barbezieux and Aubeterre formations).

A typical heterodont clam is in the upper left of this diagram; the rest are elaborate rudist clams. In the lower right is a drawing of the type of rudist photographed above. Diagram from Schumann & Steuber (1997).

Rudists flourished in Cretaceous seas right up until the mass extinction at the end of the period. They are often characterized as reef builders, but most were probably living on soft sediment substrates, like our friend here.


Gili, E., Masse, J.P. and Skelton, P.W. 1995. Rudists as gregarious sediment-dwellers, not reef-builders, on Cretaceous carbonate platforms. Palaeogeography, Palaeoclimatology, Palaeoecology 118: 245-267.

Platel, J.-P. 1996. Stratigraphie, seédimentologie et évolution géodynamique de la plate-forme carbonatée du Crétacé supérieur du nord du basin d’Aquitaine. Géologie de la France 4: 33-58.

Platel, J.-P., Faugeras, P., Mauroux, B., Spencer, C., Charnet, F., Célerier, G., Harielle, B. and Jacquement, P. 1999. Notice explicative, Carte géologie France (1/50 000), feuille Thenon, Orléans, BRGM, 128 p.

Schumann, D. and Steuber, T. 1997. Rudisten. Erfolgreiche Siedler und Riffbauer der Kreidezeit. Städte unter Wasser-2 Milliarden Jahre.-Kleine Senckenberg-Reihe 24: 117-122.

Steuber, T., Mitchell, S.F., Buhl, D., Gunter, G. and Kasper, H. U. 2002. Catastrophic extinction of Caribbean rudist bivalves at the Cretaceous-Tertiary boundary. Geology 30: 999-1002.

Unknown fossils for the Invertebrate Paleontology class at Wooster

September 1st, 2017

I start my Invertebrate Paleontology classes with an unknown fossil given to each student. I pick something I have enough examples of so that everyone gets the same species. As their first assignment, the students are asked to identify their fossils as specifically as possible using whatever method works, short of asking me or my teaching assistant. Once they’ve identified their specimens, they are then asked to provide an age and likely location of collection. The beautiful fossils above were the unknowns for this semester’s class. Do you know what they are?


These are specimens of the trepostome bryozoan Prasopora falesi (James, 1884) from the Decorah Formation (Katian, Upper Ordovician) of Decorah, Iowa. They were collected by Rachel Wetzel (’17) as part of our Team Minnesota expedition in 2016. Four of my current students figured this out to the species level! Most knew we were in bryozoan territory.

Jesse Davenport (’11) Returns to GeoClub

August 31st, 2017

Wooster, OH – GeoClub met for the first time in the 2017-2018 academic year, allowing us to catch up with old friends and meet new ones. It was our good fortune to host a special guest, Jesse Davenport, a 2011 Wooster Geology graduate. He joined us for GeoClub lunch in Lowry, reminiscing about his time at Wooster and sharing his story of life after graduation. As a special favor, he agreed to write a post about his experiences for the Wooster Geologists. Thanks, Jesse! If you’re a Wooster Geology graduate and would like to share your story, please contact Dr. Meagen Pollock.

Jesse Davenport (’11) visited the first meeting of GeoClub and shared his experiences of life after graduation.


Since Wooster, lots of thing have happened, traveling, seeing new places, meeting new, interesting people, discovering new cultures and many other things. After I graduated from Wooster, in 2011, I went on to the University of Notre Dame where I pursued a Masters degree in lunar geochemistry for two years. After this, I worked various jobs, but at the same time was searching for what would come next, whether it was a real job in some sort of geological field, a PhD program or even something else. After a few options fell through or where not that appealing I decided to apply for a PhD position that I had seen on the internet in Nancy, France (located between Paris and Strasbourg). I really didn’t know what to expect and to be honest, I thought that my skype interview with my potential advisors was the worst interview that I had ever done. But, despite this, they accepted me and with nothing else in mind that was interesting, I decided to accept this position. Now, I am not one to complain about things, but you do not know what paperwork is like until you have lived as a foreigner in France (or maybe just in any foreign country in general). It was nightmare, plus add on top of that not being able to speak French, all the culture shock and you get a scenario that would send most be people running. I stuck it out though and here I am four years later, I am almost finished with my thesis.

My PhD topic focuses around the  dynamics of weathering and erosion in the Himalayas. In the early 1990s a huge debate began, at the advent of the Ocean Drilling Program from which we now had access to oceanic records that spanned millions of years, about what are the interactions between climate, tectonics, erosion and weathering and whether that has spurred the changes we see on the Earth throughout the past 5 million years. One of the biggest questions in the Himalaya is that we would like to know how uplift and erosion has affected the global concentrations of carbon dioxide throughout the past 50 millions years. Silicate weathering (along with organic carbon burial) is one of the mechanism that mother nature uses to regulate the the amount of carbon dioxide in our atmosphere. Of course, we have had eras where these levels have been higher or lower, depending on the situation at that moment, but in general silicate weathering is the process that controls these levels. So, my PhD focuses on the isotope geochemistry of sediments, rivers and other material in the Himalaya to try to understand how the Himalaya, at present, function with respect to the dynamics between erosion, weathering and climate.

Wooster Geology Department 2017 Annual Report

August 28th, 2017

The Thirty-First Annual Report of the Geology Department is now available online with this link. Our Administrative Coordinator Patrice Reeder has once again done a magnificent job putting this document together, with amazing attention to detail and an artistic eye for format and style. Read and enjoy!

Wooster’s Fossils of the Week: Oysters from the Upper Cretaceous (Campanian) of southwestern France

August 22nd, 2017

Wooster’s Fossil of the Week returns from its summer hiatus. It is appropriate, then, to feature as our first fossil of the new season an oyster species prominent in our summer research. This is Pycnodonte vesicularis (Lamarck, 1806), a very common fossil in the Cretaceous around the world. These particular specimens are from the Aubeterre Formation (Upper Campanian, Upper Cretaceous) exposed in the town of Archiac in southwestern France. They were collected by Macy Conrad (’18), Paul Taylor (Natural History Museum, London) and me during our June 2017 expedition. Above is the interior of a deeply concave left valve. The large spot near the middle is the single adductor muscle scar (thus the oyster, like all oysters, is monomyarian). It was a free-living oyster in soft, shallow platform marine sediments. This species has been used for all sorts of studies, from investigating paleoecology and evolution to paleoseasonality (see references below for a start).

This is the interior of the right valve, showing the corresponding muscle scar. The valves are very different in size and shape, so this oyster is termed inequivalved.The exterior of the right valve, with characteristic faint radiating ridges. The tag, by the way, indicates the locality. Every one of our hundreds of oysters is tagged in this way.Macy Conrad (’18) is seen here at the Archiac outcrop collecting specimens of Pycnodonte vesicularis.

A typical bed of P. vesicularis in the Upper Campanian of SW France. This one is exposed along the sea cliffs at Pointe de Suzac.


Brezina, S.S., Romero, M.V., Casadío, S. and Bremec, C. 2014. Boring polychaetes associated with Pycnodonte (Phygraea) vesicularis (Lamarck) from the Upper Cretaceous of Patagonia. A case of commensalism? Ameghiniana 51129-140.

De Winter, N.J., Vellekoop, J., Vorsselmans, R., Golreihan, A., Petersen, S.V., Meyer, K.W., Speijer, R.P. and Claeys, P. 2017. Cretaceous honeycomb oysters (Pycnodonte vesicularis) as palaeoseasonality records: A multi-proxy study. EGU General Assembly Conference Abstracts 19: 4359.

Lamarck, J.B. 1806. Suite des mémoires sur les fossiles des environs de Paris. Annales du Muséum National d’Histoire Naturelle 7: 130-139.

Platel, J.-P. 1996. Stratigraphie, seédimentologie et évolution géodynamique de la plate-forme carbonatée du Crétacé supérieur du nord du basin d’Aquitaine. Géologie de la France 4: 33-58.

Videt, B. 2003. Dynamique des paléoenvironnements à huîtres du Crétacé supérieur nord-aquitain (SO France) et du Mio-Pliocène andalou (SE Espagne): biodiversité, analyse séquentielle, biogéochimie (Doctoral dissertation, Université Rennes 1).

Wooster Geology Professor Frederick W. Cropp III (1932-2017)

August 11th, 2017

Professor Fred Cropp taught geology at Wooster from 1964 to 1997. He was an extraordinary teacher and, in his own words, “a cheerleader for geology”. Many, many Wooster students became geologists in response to his enthusiasm, energy and spirit. I was one of them. His obituary and memorial page is here.

The Cooper Plots – Ecological Succession in Glacier Bay National Park and Preserve, Alaska

August 9th, 2017

I recently had the pleasure to work with a team of ecologists for eight days in Glacier Bay National Park and Preserve. The point of the trip was to reoccupy and expand investigations of the Cooper Plots established over 100 years ago in the wake of the retreating ice in the West Arm. A nice rundown of this ecological succession work is presented here on Glacier Hub. The ecology team recently published on their rediscovery of the plots, which was heroic considering the immense lands, intense brush and  sometimes cryptic description of the plot locations.

The accommodations and views in the West Arm of Glacier Bay were spectacular. Logistics of the project were supported by the National Park Service, who we gratefully acknowledge.

The team of ecologists included (left to right) Drs. Allison Bidlack (Director, Alaska Coastal Rainforest Center, University of Alaska Southeast), Sarah Bisbing (University of Nevada – Reno) and Brian Buma (University of Alaska Southeast). I was along to core trees at the sites (Wooster Tree Ring Lab) and to measure the size of alders.

Sarah and Brian cordon off one of Cooper’s 1-meter plots with string so we don’t trample the vegetation. Sarah reals out a 15-meter tape with Allison on the end somewhere deep in the alders. The group then carefully described the species present at each site among other observations and measurements.

The Russell Island raft served as headquarters for much of the trip.

Chasing Brian across the fjord was the typical start of a day working the Cooper Plots.

As it turns out there are multiple species of willow and distinguishing them from each other is not as straightforward as one might imagine.

Allison pauses in the West Arm on the way over to view Reid Glacier.

Not only did I learn more about the biosphere of Southeast Alaska, but I also learned something about cooking in the field and Wooster trips may benefit from this in the future.

This grizzly visited us a few times – quite possibly the most adorable bear in the region.

An excellent view of Marble Mountain looms in the distance.

Wooster Geologist in Idaho: Adventures in granite

July 26th, 2017

Gloria and I traveled out west this summer to see family and a bit of scenery. Of course, geologists are always looking for geological attractions, and we found a delightful one at City of Rocks National Reserve in southern Idaho. We visited this granite wonderland with my parents, Gary and Corinne Wilson. The weather was perfect and the rocks spectacular. Above is a view of Granite Peak on the left and Steinfells Dome on the right.

The City of Rocks (great name!) is along the California Trail of the 19th Century. Its distinctive geology is described in many emigrant journals, and several travelers left their names smeared in axle grease on some of the overhanging granite outcrops. These inscriptions are at Camp Rock.

The granite overhangs provide shelter for hundreds of mud nests constructed by American Cliff Swallows. Note the baby peeking out on the left.

There are two granites present in the City of Rocks reserve. Above is the porphyritic Green Creek granite, part of the Green Creek complex of granite, gneiss, and schist that is Archean in age, an astounding 2.5 billion years old. This is one of the oldest rocks exposed in the United States. The term porphyritic means there are large crystals interspersed with small crystals. The visible white crystals here are potassium feldspar. (Dr. Meagen Pollock, Wooster’s petrologist, will be very proud of me.)

Above is the Almo Granite, which has a more even grain size distribution. It was intruded into the Green Creek Complex only around 28 million years ago.

Here is a contact of the Almo Granite above and the Green Creek Complex granite below, with my Dad’s arm for scale. This is the igneous equivalent to an unconformity, with an almost 2500 million year difference in age between the two rocks.

A closer view of the contact. The angled dikes in the unit below are made of fine-grained quartz and feldspar, a mix called aplite.

The Almo Granite shows a peculiar kind of weathering called tafoni. The outer surface of the rock acquires a resistant crust through weathering, a process called case-hardening. Apparently in this case the hardening is due to the dissolution of silicate minerals, which reprecipitate as hard silica-rich minerals. The softer rock underneath is then dissolved by salty water (the salt probably coming through dust blown from evaporative salt flats), resulting in small cavities and caves like the one above.

The tafoni and case-hardening is also visible in this Green Creek granite outcrop.

The case-hardened layer can slip off rounded surfaces through exfoliation of the granite domes, sometimes leaving a small resistant remnant on the very top. These remnants are called pickelhauben because of the resemblance to the spiked World War I German helmets. This monolith is termed, in fact, Kaiser’s Helmet.

Another distinctive form of chemical weathering of the granite produces panholes. These have flat bottoms rather than the rounded bottoms of potholes.

Dr. Shelley Judge, Wooster’s structural geologist, will love the joints visible in this granite body. Joints are fracture sets along which there is no movement (thus they are not faults). The joints here are complex and probably related to thermal contraction as the granite pluton slowly cooled underground.

This is my favorite monolith in the reserve. It shows a combination of the spherical exfoliation of the granite dome and a consistent set of joints cutting through it.

Joints dominate the Almo Granite exposed at our picnic site.

Finally, the granite outcrops at City of Rocks National Reserve are a famous destination for rock climbers. In the center here is one of the best-known climbing sites, Morning Glory Spire. At the tippy top you might be able to see two climbers standing there enjoying the view and their accomplishment.

Thank you to my parents for suggesting this trip (and Dad for driving). It is a geological paradise, even if there isn’t a fossil for miles.


Meanwhile, what are the Wooster Paleontologists up to?

July 19th, 2017

Wooster, Ohio — The igneous petrology team has a thorough and entertaining report about their activities in the Wooster geology labs this summer. It has encouraged the summer paleontologists (that would be me and Macy Conrad ’18) to give a progress report. Compared to the high-temperature geochemistry going on in the basement, we are decidedly low-tech upstairs in the Paleo Lab!

Above is our set of fossil oysters (Pycnodonte vesicularis) from the Campanian (Upper Cretaceous) of southwestern France we collected this summer. Each oyster has been cleaned, labeled, and given its own tray. We’ve examined each specimen in a preliminary way to sort out the prominent sclerobionts (hard-substrate dwellers, like encrusters and borings). So far we’ve determined which have bryozoans, serpulids, sabellids, foraminiferans and bivalves attached to them, and we’ve recorded the types of borings we see on each, which makes an impressive list: Entobia, Rogerella, Maeandropolydora, Gnathichnus, Radulichnus, Talpina, Belichnus, Oichnus, and maybe Podichnus.

The diverse encrusting bryozoans are the greatest challenge, and they will produce the most interesting and rich data for our paleoecological and evolutionary hypotheses. These fine creatures are difficult to identify, but we have one of the world’s greatest bryozoologists on our side: Paul Taylor of the Natural History Museum. He gave us a large computer file of scanning electron microscope (SEM) images of the most likely bryozoans we will encounter. We printed each of the 232 images as our “mugshots”. We have started with the uniserial and multiserial cyclostome bryozoans because they’re the easiest recognize. When we see one, we identify the specimen with a pink tag.

This microscope is our most sophisticated equipment so far! Later we will scan our best specimens in London on Paul’s SEM.

Here’s a tray of oysters from the Aubeterre Formation with the beginning of our colorful tagging. Laborious, detailed work, but already we see that the diversity of sclerobionts will generate some good stories.

Future updates will include some of our own photomicrographs!

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