Wooster Geologists

I was so impressed with the post by Professor Greg Wiles about his Fall 2022 Geomorphology class that I decided to highlight the Fall 2022 Paleoecology class as well. It was a great group of students, and we did an extraordinary amount of scholarly work: 26 quizzes, two tests, one final exam, two essays, a research paper, a research presentation, an extensive field project, and three other lab reports. They flourished and in turn through their research taught me quite a bit about many paleoecology topics. We were assisted throughout by our brilliant, patient, tireless, cheerful Teaching Assistant Brianna Lyman.

Early in the course we had a day-long field trip to southeastern Indiana (locality C/W-148 near Richmond) described in an earlier post. The goal was for each student to make a large collection of fossils from the upper Whitewater Formation (Upper Ordovician) that would be the raw material for a detailed paleoecological report due at the end of the semester. Nick Wiesenberg, our geological technician, was invaluable in the planning and successful completion of this little expedition.

These are the filled sample bags from the field trip, one for each student.

The next step was to wash the specimens for further analysis.

One of the student trays with typical specimens from the trip, including brachiopods, bryozoans, bivalves, gastropods, corals, cephalopods, monoplacophorans, and a few rare trilobites. There were also trace fossils, including numerous borings in the calcitic shells.

This is a completed tray at the end of the semester. Specimens are cleaned, labeled, and identified. Each student made at least two acetate peels, one from a rugose coral and the other from a bryozoan. Each student then wrote a report on the taxonomy, taphonomy, and paleoecology of their collection, supplementing their observations with the discoveries and ideas of their classmates. It was a nice mix of individual research and group discussions.

Another lab exercise detailed the ontogeny of the rugose coral Grewingkia canadensis from the same field site. We clearly have enough specimens for each student to measure the dimensions of numerous corals. They then used a statistical package (Past4) to make various graphs for interpretations.

We also had a foraminiferan “picking” exercise. Each student had a vial of sediment from a drill hole in the Gulf of Mexico (Frio Formation, Oligocene). They then collected foraminiferan tests with a thin wet brush and placed them on slide covered with water-soluble glue.

The process required careful hand-eye coordination to not lose the little critters in the transfer from sediment to tray!

This image shows a sediment vial, a picking brush, and a completed slide. Each number on the slide has a tiny specimen glued by it. The students then identified the foraminiferans and assessed the likely depth that the benthic forms lived.

The final exercise involved identifying shark teeth from the Cretaceous Menuha Formation of southern Israel. We have a large collection of these teeth from the Independent Study thesis of Andrew Retzler (’11). We used Retzler et al. (2013) as our guide for identification of these sharks and their paleoecological context.

I had an excellent time in this course with these creative, hard-working, resilient, happy students.

This is a post outlining some of the work we did in Wooster’s class in Geomorphology. One of the early labs was Browns Lake Bog and the Soil Catena.

The landforms in the area are spectacular – here is a kame, a photo taken  as we ventured down into the bog.

The group shares a light moment before the 20+ species of mosquitos descended on them in the forest.

The soils from the top of the kame to the base varied more than the group predicted.

We also sampled soils just east of the campus golf course.

Nick and Jerry in the soil pit measuring magnetic susceptibility as Des records the data.

The C-horizon on the left is a sandy, silt gravel – the B-horizon in the middle is blocky loam and the A is a more brown silty material.

The team coring an old growth (300+ year) tree growing on top of the soil site. The landform is a kame terrace that has likely been weathering in place for the last 14,000 years with additional windblown silt being added (or removed) from time to time during the Holocene.

At Zollinger’s Sand and Gravel – posing at the base of the section which is Mississippian bedrock. A big thank you to the Zollinger family for allowing us to work here and for showing us around.

This side of the pit is still being mined, whereas other portions serve as land fill. We learned that lodgement till can be fractured and that it also can be mined and serve as a landfill liner.

On the way back to campus we stopped at the artesian spring near the Wayne County Airport.

Of course not class would be complete without a trip to Spangler. Here the group is standing inf ront of one of the unconformities, which is composed of a lodgement till overlain by fluvial and alluvial sediments.  The interface of these units is where the geochmistry is just right to generate concretions.

The increasingly greater precipitation events are moving larger and large block of bedrock. Here the Wooster Shale is being excavated by 1-2 inch storm events. Our hypothesis is that erosion rates over the last few decades are unprecedented perhaps over much of the Holocene.
Big blocks are moved routinely – they are plucked out by the stream along planes of weakness (fractures). Note how the shales break up readily. A block like those above will be mud again in a matter of months. Swelling clays and strong wetting and drying does the job.

Here is a series of debris flows (gray sediment) – we obtained two radiocarbon ages that show intervals of mass movements about 2.5 ka, these are dates on charcoal that may be from fires used in land management by native Americans at the time.

Stream gaging along Apple Creek. The group gets some hand-on experience with the equipment and puzzles over the various facies of a fining upward fluvial sequence.

Nick and Tyrell take turns in the deep end.

Jack giving the group the rundown on riparian vegetation.

As it turn out the floods here get pretty high, this tree was scarred when a log (or a washing machine) floated by during a high flow.

The class at Fern Valley standing in front of Columbia Gas’ well-head for the natural gas storage field. The group was investigating the possibility that mass movements at the site might impact the infrastructure and pipelines in the area.

The slump block at Fern Valley is clearly seen from above. It is a series of glacial ice-contact stratified drift deposits overlain by a thick (40+ foot) layer of varved lacustrine clays. What you see in the woods is a major 2-3 meter scarp (normal fault) as the block descends into the valley.

The class at Fern Valley. A big thank you Nick Wiesenberg for arranging the logistic for the trips. We would also like to thank bus drivers Mark Livengood and Fred Potter for getting us to and from the sites safely. A special thanks to Fred who will be retiring soon – we appreciate your expertise and knowledge of the Wooster area.

Our hard-working and observant Estonian colleagues (Olev Vinn and Ursula Toom) recently made a remarkable discovery among Estonian early Silurian fossils: an attachment structure of a stalked crinoid that apparently bioeroded its way into a calcitic stromatoporoid skeleton.

There’s a lot packed into that opening sentence. (And you’ve noticed that “remarkable” is a relative term depending on your interests!) For orientation, a crinoid is an arm-bearing, filter-feeding marine echinoderm with a very long evolutionary history to the present day. They have skeletons of calcite typically consisting of a flower-like crown with feeding appendages, a stem (or stalk) made of stacked disks, and some sort of holdfast structure. That holdfast can be quite variable, from roots in muddy sediments to thick disks cemented to hard substrates.

Generalized diagram of a crinoid drawn by our coauthor Bill Ausich.

Bioerosion is the biological erosion of a hard substrate by either mechanical means (grinding, rasping, scraping, biting, drilling) or chemical (such as acidic dissolution) producing structures like borings, grooves, drillholes, etc. Until this work, no crinoids living or extinct have been known to bioerode their substrates. Here, though, as you can see in the top image, we appear to have a crinoid that has done just that way back in the Silurian.

The top image is of a thin-section cut through a crinoid holdfast attached to a stromatoporoid, which is a kind of calcareous sponge with a dense, layered skeleton of calcite. The whitish vertical portion is the crinoid stem partially buried in sediment. The yellow arrows show the radices (essentially “roots”) of the crinoid penetrating into the stromatoporoid skeleton, cutting through its topmost layers. It is clear that the crinoid was not simply embedded in the skeleton by stromatoporoid growth — the radices cut through the layers. This crinoid bored into the stromatoporoid (probably chemically) and held on tenaciously. Remarkable. The first indication that a crinoid could do this sort of thing.

Thus far it is only one specimen, so there is the inevitable question mark in the title of this paper. We put it out there as a first report hoping that other such cases may be found. Or, of course, someone could show that our interpretation is not correct.

I love these paleoecological stories! Thank you again to our Estonian friends and colleagues Olev Vinn and Ursula Toom. Bill Ausich and I treasure our friendship and collaboration with them.

For the record, this is the location of the boring crinoid find (from the paper).

And this is the stratigraphy (from the paper).

Reference:

Vinn, O., Ausich, W.I., Wilson, M.A. and Toom, U. 2022. Did stalked echinoderms bioerode calcareous substrates? A possible boring crinoid attachment structure in a stromatoporoid from the early Silurian (Telychian) of Estonia. Paläontologische Zeitschrift (https://doi.org/10.1007/s12542-022-00637-3)