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.

References:

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!

High-Temperature Geochemistry in Action

July 18th, 2017

WOOSTER, OH – Over the last couple of weeks, our Keck Geology Team Utah has been hard at work in the College of Wooster Geology labs. We collected a dozen samples from Ice Springs Volcanic Field in the Black Rock Desert, Utah to understand the eruption history and the age of the lava flows.

The first processing step is to powder the sample. Addison Thompson (’20, Pitzer College) uses the rock saw to isolate pieces of fresh rock.

Addison and Madison Rosen (’19, Mt. Holyoke College) use a sledge to break the sawn pieces into smaller bits.

Sam Patzkowsky (’20, Franklin and Marshall) cleans the chips so that we can crush them in the shatterbox.

Emily Randall (’20, College of Wooster) sieves the powder and makes sure all of it is small enough for the next step. We sent some of this powder to the Purdue PRIME Lab, where they’ll measure the abundance of 36Cl in our rocks.

Pa Nhia Moua (’20, Carleton College) pulls samples out of a red-hot oven so that we can measure Loss on Ignition (LOI) to determine how much H2O might be in the samples.

Sam and Addison weigh out accurate amounts of the oxidized sample and flux, which lowers the melting temperature and helps our samples melt so that we can make glass discs.

The samples get melted in the fluxer and poured into molds to make glass discs.

The glass discs are loaded in the XRF and analyzed for their major element chemistry. We use the chemistry along with the data from Purdue and the location and orientation of the sample to calculate an age for the lava flow.

We’re using another method called Varnish MicroLamination (VML) dating to provide an independent estimate of the age of the lava. Desert varnish is a dark coating of clays and iron- and manganese-oxides that accumulates on the surface of samples in arid environments. You may have seen ancient petroglyphs carved into the desert varnish. Researchers use the layering in VML to date pieces of rock art. In order to use the VML method, we have to make ultra-thin slides of our rocks so that we can see through the varnish.

Addison pours epoxy into plastic molds to mount the VML samples.

Pa Nhia has been sanding her VML sample for days to grind it to the correct thickness without grinding away the varnish. It’s dirty, delicate work.

By the end of the week, we should have age estimates for the lava flows and a better idea of the sequence of eruptive events that formed Ice Springs Volcanic Field. Check back later for our GSA abstract!

Exploring the Geosciences at Zion National Park

July 10th, 2017

Zion National Park – Dr. Wiles and I are directing a 5-week undergraduate research project through the Keck Geology Consortium‘s Gateway Program. The Gateway Program has two goals: engage the students in an authentic research experience while exploring the intersections between the geosciences and society. Three weeks into the project, the students have collected tree cores and lava samples in Alaska and Utah, respectively, and are hard at work processing those samples in the Wooster labs. In the meantime, the students have explored the geosciences by talking with geoscience professionals and visiting locations like the Utah Geological Survey and Zion National Park. Here are Team Utah’s reflections on the intersections between geoscience and society, in their own words:

Pa Nhia Moua (’20, Carleton College)

On June 27th, 2017, Team Utah from the Keck Geology Consortium visited Zion National Park. Before Keck, I had never visited a national park before, so I was really excited to see how a national park differed from a “regular” city/town park. To my surprise, when we first arrived, I felt like I was at Disney world again or at the state zoo (Minnesota Zoo). As we continued into Zion, I realized how commercialized Zion was. Gift shops greeted customers on their way in and out, park rangers available for information (but to me they seemed like tour guides), and the long line of people (waiting for shuttles). The amount of commercialization astounded me as I was not aware how popular a national park could be. After splitting up, part of Team Utah traveled to venture the Riverside Walk, where we had our lunch. We sat on the riverbank, on rocks and trees, under the shade. As I ate, I found myself often wondering about the formation of the landscape. I wondered how much things had withered away, and what was originally there and what had come later. After lunch, we walked the riverside path and we continued onto the Narrows. It was here where I really got a good look at how other people interacted with the landscape and everything else around them. Majority of the people would look up at the sky in admiration of the stone walls that created the “narrows” and kept the formation of the river. But, as I ventured deeper into the Narrows, I noticed that the only time people took in the scenery was in the beginning. Majority of the people interacted with the water, as they were trying to keep from falling while catching up with their groups. I feel that because of the Keck Geology Consortium program, my experience at Zion has been enriched by the knowledge I have acquired (while in the program). Since my participation in the program, I have become more conscience about the world around me. I wonder more about the history of where I go and what I see. Because of such thoughts, I feel that my knowledge deepened my meaning and experience at Zion.

Pa Nhia stands in the Narrows in Zion National Park.

Sam Patzkowsky (’20, Franklin and Marshall)

Zion National Park is one of the most beautiful places that I have visited in the 19 years I have been on this Earth.  The geology of the park was unlike anything I have ever seen before and I was blown away by the amount of people who were at the park.  Geology plays a huge role in the National Park Service; since there are many national parks that are centered around geology.  What astounds me is that people know how appealing these parks are to people and that there are those who know take advantage of this and make a living of it.  When I think of the word “tourism,” I think of hotels on white sand beaches during prime summer hours.  This, however, isn’t the case with a place like Zion National Park.  There are the typical hotels and inns located in the town just outside of the park, but there are also shops that try to take advantage of people’s curiosity about the rocks and the geology.  I am really happy to see this because it means that if a shop can sell someone a cool looking rock, then maybe they’ll start to ask questions like: “how did this form?” “what is this made up of?” “where can I find things like this?”.  If even one person’s life changes because of looking at these tourist shops, I will be forever grateful because the seed of geology is being planted in their mind and hopefully it’ll grow into something breathtaking.  Tourism is something that is crucial to the interaction between the public and geology and I hope it can help change lives for the better.

Team Utah at the Zion National Park entrance.

Emily Randall (’20, College of Wooster)

One of the biggest things I noticed at Zion National Park was what seemed to be the lack of interest in the geology. When people arrived at each location they would glance at the features surrounding them a few times before proceeding to a task that then took all of their attention. Where I was, this was either playing in or wading through the river, but I’m not sure about other locations. Luckily, whether people realized it or not, these types of tasks forced them to interact with the geology around them. I also appreciated that the Parks Services had audio about the park and its geologic features playing on the bus, which some people listened to but a lot seemed to talk over. I’m not sure what could be done to make the, what I see as impressive, rocks beat out the water on a scorching summer day like the one we visited during, but I hope my impression was skewed since I visited the river. Though, this was to view the impressive narrows and the striking cliffs as opposed to play in the water.

Hiking the Narrows at Zion on a 100+ degree day.

Madison Rosen (’19, Mt. Holyoke)

Utah is a beautiful state filled with many different types of geology, from 20 feet high dinosaurs to brine shrimp that are less than a inch long. During my weeklong stay in Utah, I was able to experience most of what it was famous for. This included, Zion National Park, Salt Lake, Natural History Museum of Utah and the Geological Survey of Utah. My favorite was Zion National Park, because of its enormity and beauty. At Zion National Park the erosional effects of water on sandstone was easily seen, but the average park goer was not focused on the geology of the park. Instead thousands of people would stand in a theme park like line to get the perfect picture on top of these geological landforms. On the shuttle bus, a quick description of how Zion was developed was announced, but not everyone was paying attention to the 30 second long segment. Unlike other parks that I have been to, many of the people were rushing to get from one spot to the next, making for an almost chaotic atmosphere at times on the popular trails. The sheer number of people was overwhelming, but I had a wonderful time seeing enormous sedimentary structures and learning about Zion. Geology and society interact minimally, but not limited to if the visitor wants to learn more by asking employees of the park. People who visit the Natural History Museum are more open to learning how things happened in an interactive setting. While at the Geological Survey certain groups or companies go there with the purpose of learning about a particular core. The audience’s intention of visiting a certain place really determines how much knowledge that they will gain from that experience. It was really special to get to see the geological features of Black Rock Desert, Zion National Park, Salt Lake and what the Natural History Museum of Utah and Geological Survey of Utah does to interact and involve the public.

Team Utah learning about the cores stored at the Geological Survey of Utah.

A picture of Zion National Park on the 100-degree day Team Utah visited.

Addison Thompson (’20, Pitzer College)

How does geoscience intersect with society?

Water is one of the most basic needs to a human.  When examining a map, it is easy to recognize that most major cities have been constructed in close proximity to a substantial water source due to the ease of access.  When visiting my relatives in the small rural town of Biglerville, PA, I was never quite sure how they acquired their water.  They are near no river nor suitable water source, yet water flows from their tap just as it does in my home, Baltimore.  The answer for their water source is a well.  Far beneath their town is an aquifer, which can be tapped for water.  The aquifer is usually made of sandstone and water can remain in the sandstone because of the stone’s high porosity.  To create the well, a pipe system is drilled into the porous sandstone and the water in extracted.  The geologic phenomenon of the creation of an aquifer enables my cousins to live in their small rural town and sustains thousands of other towns which lay far away from usable surface water sources.  This usage of aquifers as a water source has allowed people to move where they please and into more remote places previously believed to be uninhabitable because of the lack of water, however it has always been just below us.  The presence of aquifers has helped humanity spread to the corners of the world.

While in Zion, Sam Patzkowsky and I witnessed the aquifer process from an interesting vantage point.  Usually the sandstone that comprises an aquifer is underground, however during our hike, there were sandstone slabs above ground in which it could be seen that water was seeping through.  Most notable of these being weeping rock, a sandstone block from which water seeps thus personifying weeping.

 

 

The Northern Pacific Coastal Temperate Rainforest (PCTR)

July 4th, 2017

The high rainfall and high coastal ranges nourish the icefields of southern Alaska along and with the extensive carbon-rich forests and ecosystems of the Northern Pacific Coastal Temperate Rainforest (PCTR).

Chris surveys the North Pacific noting the extensive moisture source and ocean pasture that is just offshore of the terrestrial ecosystems we are studying.

Malisse sits atop a shore pine, another slow growing coastal species that is experiencing potential decline.

Kerensa sites atop an obducted ophiolite – we were 71% sure that there were pillows in the basalt.

Josh cores another Alaska Yellow cedar – we were able to sample three sites in the Juneau area. These cedars are in decline due to warming and loss of snowpack, which makes their fine roots vulnerable to frost. Our objective is to work up the tree-ring record of the sites to contribute to our understanding of the decline.

Alora takes a break from taking notes and GPS coordinates for each tree.

Ice caves fund to explore and act as a conduit to meltwater and warm air accelerating the melt.

Blue the dog – takes a break from pursuing porcupines in the muskeg.

Nick of the Ophiolite.

Kerensa wades through the deep texture of coastal carbon.

Buried forests emerge from the wasting margin of the Mendenhall Glacier.

Nugget Falls – this is a classic hanging valley that has been revealed by the Mendenhall Glacier over the past 80 years.

A granite erratic just offshore.

A marmot sites on a stone in front of the emerging shoreline and new stands of Sitka Spruce.

A recently stripped cedar. The Tlingit strip the trees for a variety of reasons, primarily to procure the inner bark for weaving.

The field group taking a rest on the way back from Cedar Lake. The group is now working intensively on the Yellow Cedar cores to develop the tree ring record.

Thank you Jesse Wiles for your excellent photography and logistical support.

Team Alaska’s Last Day

July 3rd, 2017

To wrap up an incredible journey, Team Alaska scrambled over glacially-scoured rock faces and occasionally bush-whacked through thick shrubbery to Mendenhall Glacier. Small glimpses of the glacier that were periodically revealed through high points or gaps in the forest

Approaching Mendenhall Glacier…can you spot the people for scale?

Subglacial hydrology, captured within an ice cave #NoFilter

Malisse, Chris and Kerensa explore the Ice Caves beneath the Mendenhall Glacier.

Jesse treks out onto the vast, icy terrain

Team Alaska plays follow the leader to get off the glacier safely

Alora coring subfossil snag trees from the Little Ice Age.

Taking in the immensity of the glacier

French oysters. Aged to perfection.

June 30th, 2017

Wooster, Ohio — After our glorious fieldwork in France earlier this month, the Campanian (Upper Cretaceous) oysters Macy Conrad (’18), Paul Taylor (Natural History Museum, London), and I collected are now in our cozy Wooster Paleontology Lab. Now the less glamorous work begins: washing, sorting and labeling the specimens. Macy is shown at work with the collection arranged by localities.

This part of the work requires very low-tech equipment: scissors, paper, and water-soluble white glue. Generations of Wooster students know this procedure. Every specimen must be labelled with a number indicating its locality, even if we have hundreds of them. Paleontologists worry a lot about losing the context of a specimen, so we are obsessive about labelling. First we give a C/W code to each locality, print the numbers by the hundreds, cut them out, and then glue them to appropriate places on each fossil. White glue is great because it is easy to use, non-toxic, and it dissolves in water in case we need to remove or change a label. I learned this simple process in graduate school.Here are some fossil oysters with our coding sheet above.
A close-up of labeled specimens. We place the labels on matrix stuck to the fossil if possible.

These are the customized tags we’ll eventually fill out for each specimen recording our observations of the sclerobionts (hard-substrate dwellers like encrusters and borings). This will keep Macy and me busy for a long time. It’s not dramatic work, but we thought you might like to see all aspects of paleontological research through this project. More to come!

« Prev - Next »