Wooster’s Fossils of the Week: A molluscan assemblage from the Miocene of Maryland

July 15th, 2016

1 Calvert Zone 10 Calvert Co MD 585Earlier this month a gentleman stopped by The Department of Geology and donated the above beautiful slab of fossils to our program. Dale Chadwick of Lancaster, Pennsylvania, is an avid amateur fossil collector with a very useful website and considerable generosity. His gift to the department makes an excellent Fossils of the Week entry. Later I’ll show you the equally-impressive other side of this specimen!

We have here a fine sandstone from the famous Calvert Formation (lower to middle Miocene) exposed at the Calvert Cliffs, Plum Point, Calvert County, Maryland, in the stratigraphic Shattuck Zone 10. As you can see, some horizons are densely fossiliferous with large numbers of gastropods and bivalves. This is what we refer to us a death assemblage, meaning these shells are not preserved in their life positions but how they accumulated just before final burial. These rocks and their fossils were the initial basis of Susan Kidwell’s important work on taphonomic feedback, or how shell accumulations affect the succeeding living communities.

So what are the prominent fossils in this slab? Dale has the answers on his website. I’ve annotated the image and made a list below:

2 Calvert Zone 10 Calvert Co MD 585 labeledA Turretilla variabilis (a turritellid gastropod)
B Stewartia sp. (a lucinid bivalve)
C Turritella plebia (a turritellid gastropod)
D Cardium laqueatum (a carditid bivalve)
E Siphonalia devexa (a buccinid gastropod)

So how did several of these animals die on that seafloor long ago? You’ve probably guessed predation by looking at that round hole in specimen B, a lucinid bivalve.

3 Naticid borehole Calvert 585The beveled nature of this round drillhole tells us it was made by a predatory naticid gastropod, which used its radula (a tongue-like device with sharp teeth) to penetrate the calcareous shell and damage the muscles holding it tight against the attack. About half the specimens in this slab show similar predatory penetrations. Wooster alumna Tricia Kelley did critical work on predation styles, intensities and evolutionary patterns with Calvert specimens like these.

Thank you again to Dale Chadwick for his gift!


Kelley, P.H., 1983, Evolutionary patterns of eight Chesapeake Group molluscs: Evidence for the model of punctuated equilibria: Journal of Paleontology 57: 581–598.

Kelley, P.H. 1988. Predation by Miocene gastropods of the Chesapeake Group: stereotyped and predictable. Palaios 3: 436-448.

Kidwell, S.M. 1986. Taphonomic feedback in Miocene assemblages: Testing the role of dead hardparts in benthic communities: Palaios 1: 239–255.

Kidwell, S.M., Powars, D.S., Edwards, L.E. and Vogt, P.R. 2015. Miocene stratigraphy and paleoenvironments of the Calvert Cliffs, Maryland, in Brezinski, D.K., Halka, J.P. and Ortt, R.A., Jr., eds., Tripping from the Fall Line: Field Excursions for the GSA Annual Meeting, Baltimore, 2015: Geological Society of America Field Guide 40, p. 231–279.

Wooster’s Fossil of the Week: An ammonite from the Middle Jurassic of southern England

July 8th, 2016

Leptosphinctes microconch Jurassic Dorset 585We’re featuring just a workaday fossil this week because of other summer activities. This is the ammonite Leptosphinctes Buckman 1929 from the Inferior Oolite (Middle Jurassic) at Coombe Quarry, Mapperton, Dorset, southern England. Cassidy Jester (’17) and I collected it last month during our 2016 England research expedition. Our friend Bob Chandler generously identified it. It popped out of a rock we were pounding into submission, providing a direct application of ammonite biostratigraphy to our work. As with many ammonites, the group is well known but the names are still a bit dodgy.

This specimen is a microconch, meaning it is the smaller version of a species pair, the larger being the macroconch. It is presumed that this is sexual dimorphism and that the microconch is the male because it didn’t need to carry resources for egg-laying. This is one reason why the taxonomy of these ammonites is in perpetual revision.


Buckman, S.S. 1909–1930. Yorkshire Type Ammonites & Type Ammonites. Wesley & Son, Wheldon & Wesley, London, 790 pl.

Chandler, R B., Whicher, J., Dodge, M. and Dietze, V. 2014. Revision of the stratigraphy of the Inferior Oolite at Frogden Quarry, Oborne, Dorset, UK. Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen 274: 133-148.

Galácz, A. 2012. Early perisphinctid ammonites from the early/late Bajocian boundary interval (Middle Jurassic) from Lókút, Hungary. Geobios 45: 285-295.

Pavia, G. and Zunino, M. 2012. Ammonite assemblages and biostratigraphy at the Lower to Upper Bajocian boundary in the Digne area (SE France). Implications for the definition of the Late Bajocian GSSP. Revue de Paléobiologie, Vol. spéc, 11: 205-227.

23 Hours of Sunlight and 22 Hours of Bugs (Part 2)

July 5th, 2016

Guest bloggers: Andrew Wayrynen and Jeff Gunderson

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We take our berry picking very seriously

Oh so you thought you got rid of Team Alaska, didn’t you? Yeah well, just as there are as many cedar sites in Juneau as there are cruise ship tourists, we’re back with part 2. Now where were we?

After our Kayak at McBride Glacier amongst the massive icebergs in the fjord, we— Jesse Wiles, Dr. Wiles, Jeff Gunderson, Andrew Wayrynen, and Nick Weisenberg— decided to take to the ice by foot. As such, the following day we made the short kayak to the outwash plain at the terminus of Riggs Glacier, a massively cold testament to what the coastal Alaskan climate can do. While on the glacier, it was impossible not to feel humbled and awe-struck by its enormity. It was a friendly and welcome reminder as to why the science truly matters.


A Jeff for scale at Riggs Glacier

Exploring Riggs glacier was a wonderful experience, but the time soon came for another dendroclimatological expedition. Our goal was to search for wood in the recently vacated valley where once Riggs and McBride Glaciers connected. To our pleasure there was hardly any alders, which made the mission less trying, yet there was no shortage of braided streams that provided ample opportunities for a boot full of freezing glacier water. Unfortunately, there was only one log to be found and sampled in the entire valley. As sure as the bugs did bite, we brought it home.


Dr. Wiles coring the lone log in the valley

The following day, an all-too-familiar gray haze took command of the skies that dripped upon us a rather watery substance called rain. As the bold, rugged mountain-worn scientists slated to bridge that 2000-year gap, we took the day off. We explored our camp cove and admired huge beached icebergs.


Andrew investigates the dead ice 

 That day at our camp in Muir Inlet would prove to be our last, as Todd, the wise NPS boat captain, arrived in late morning of the following day with Dan Lawson to take us to Tlingit Point. However, we made a historically significant stop along the way. Before navigating Glacier Bay’s icy waters, Todd worked in Yosemite Valley in California, inadvertently following John Muir’s footsteps in his late 19th century search for glaciers. Much to Andrew’s excitement, he guided us to the site of John Muir’s cabin, which was built in 1879 by Muir and friends. Having been so busy as geologists, our crew relished in the opportunity to have a stab at archaeology.


 John Muir’s cabin in the late 19th century where the terminus of Muir Glacier once was (left) and the same cabin today (right)

Now camped at Tlingit Point, we had our sights on the Mountain Hemlock situated atop the hills above us. The climb up was incredible in practically every sense of the word. While ascending, the chances of peering out to the bay and soaking in the gorgeous vistas were about the same as falling into patch of delicious wild strawberries. Near the top, the alders thinned and the brush only came up to ankle-height, but alas the bugs persisted, hungrier than ever. Once amid the old growth, we cored the mighty hemlocks and safely tucked away the obtained samples.


Andrew tries his hand at coring for the first time


Mountain goats became new friends to the Wooster Geology Department

 Things we learned: Giant Hogweed makes your skin more susceptible to UV rays and can cause third degree sunburns (no, those puss bubbles on your hand aren’t spider bites, Jeff). It doesn’t really rain in Alaska- spare your wallet and don’t buy rain gear if you go. Apparently, Alaskan mosquitoes are wildly undernourished. Dendrochronology/Dendroclimatology is amazing. Our favorite rock is becoming a tree.


The view from the top of Tlingit Point marked the end of an awesome field season

Keck Students Doing Rock Hard Research

July 4th, 2016

Hafnarfjörður, Iceland – Guest Blogger Ben Kumpf (’18)


Keck students doing recon on the volcanic ridge system they will be studying for their senior research projects. Dr. Ben Edwards on right giving one of his many field lectures on the petrology and physical geology of the area.



Lava bears were an unexpected encounter when climbing the ridge. These bears just happened to come out of the cave when Dr. Meagen Pollock was analyzing an outcrop of her favorite rock, none other than basalt.

Basalt here, basalt there, basalt everywhere. Long days in the field with endless sunlight wore out these tired lava bears. It seems they have found their favorite napping spot on a nice piece of moss.






A volcanic intrusion known as a dike sticks out of the surrounding lapilli tuff and tuff breccia units on top of the volcanic ridge system. Features like these are important to the project. The Keck students will be working to map in new features which are critical step in the process of updating the map of the ridge.

Ben Edwards and his field assistant Will Kochtitzky surveying a gully on the south side of the ridge as part of a mapping project to be done during the Keck experience in Iceland.

The Sulfur Saga

July 3rd, 2016

Hafnarfjörður, Iceland – Guest Blogger Ben Kumpf (’18)


Sulfuric gas rising with steam from the water heated from a subsurface magmatic intrusion. If you ever wanted to smell a volcano this would be a great stop in Iceland, however you should bring some nose plugs because this  place will really take your breath away.


Our slimy little friend also enjoying the pungent smell from the geothermal vents. It looks like he’s trying to catch some fresh air and maybe some TV with those Martian antennas.


Part of the perks of coming to Iceland is definitely the breathtaking views you can get from just about anywhere on the island. This one in particular is from the top of the geothermal area at the end of a long field day.

A Journey to the Land of Basalt

July 2nd, 2016

Hafnarfjörður, Iceland – Guest Blogger Ben Kumpf (’18)


One of the many “pillow talks” the Keck students were having as they were analyzing vesicle patterns and jointing of pillow basalt. Dr. Pollock’s expertise in MORB’s and pillows along the ridge was very helpful to further research in sub-glacial eruptions.


A great view of one of the main field locations in Iceland, Undirhlíðar Quarry. This location gives the young researchers a cross sectional view of the ridge, shedding light on the stratigraphy of the Northern end of the ridge.




From left to right: Michelle Orden (Dickinson ’17) and Anna Thompson (Carleton ’17). One of the best exposures of the trip was a near vertical dike with a well preserved glassy contact.



Who would expect to find a burger in the middle of a lava field?! A little crunchy and slightly vesiculated this sub-glacial burger is packed with flavor and phenocrysts.


Vesicles and phenocrysts are great characteristics to help differentiate pillow units. The large white dots are plagioclase phenocrysts and the yellow to green dots are inclusions of olivine.




An Experience and an Upset

July 1st, 2016

Reykjavik, Iceland – Guest Blogger Ben Kumpf (’18)


Carl-Lars Engen (Beloit ’17), among thousands of Islanders gathered in the capital, Reykjavik. Fans were cheering on the national team in the Euro Cup round of 16 against England. We were fortunate enough to see one of the biggest upsets of the year as a country with more volcanoes than professional soccer players defeated England 2-1.


Wooster’s Fossils of the Week: Iron-oxide oncoids (“snuff-boxes”) from the Middle Jurassic of southern England

July 1st, 2016

1 Snuffbox colection BBThese fossils (in the broad sense!) are inevitable for our weekly feature considering how much time we spent studying and collecting them during last month’s fieldwork in Dorset, southern England. “Snuff-boxes” are the subject of Cassidy Jester’s (’17) Senior Independent Study project, so here we’ll just broadly cover what we think we know about them.

These discoidal objects are called “snuff-boxes” because their carbonate centers (usually a bit of limestone or shell) often erode faster than their iron-oxide exteriors, making them weather a bit like boxes with lids.
2 Quote from Buckman 1910 67This quote from Buckman (1910, p. 67) is the earliest reference I can find to the snuff-box term. Snuff-boxes were sometimes works of art in the 18th and 19th centuries, although quarrymen probably had more homespun varieties in mind.
1 Snuffbox serpulidssWe’re counting these snuff-boxes as fossils here because they formed through biotic and physical processes. The cortex of a snuff-box has layers of serpulid worm tubes, as shown above.
4 Palmer Wilson Fig 3There are also cyclostome bryozoans embedded within the iron-oxide layers, as shown in this image from Palmer and Wilson (1990, fig. 3).
3 Snuff-box horn 061716We believe the snuff-boxes grew by accretion of microbially-induced layers of iron-oxide formed on their undersides, which would have been gloomy caverns on the seafloor. They then would have occasionally turned over and grew layers on the other side. Many snuff-boxes have extensions on their peripheries that look in cross-sections like horns, as seen above. The layers are separate from those that formed around the nucleus. They may have grown after the snuff-box became too big to be overturned by currents or animals.
6 Platy minerals pdt19573Paul Taylor and I looked at the cortex of a snuff-box with Scanning Electron Microscopy (SEM) and had the above surprising view. The odd platy materials may be limonite, an iron-oxide that is amorphous (non-crystalline).
7 Hebrew letters pdt19572Sometimes the plates look like they’ve partially evaporated, leaving remnants that resemble Hebrew letters!
8 iron ooid pdt19576Associated with the snuff-boxes are small “iron ooids” that are about sand-size. They too have the platy materials, and so their origin may be similar to that of the snuff-boxes.

Cassidy has an interesting project ahead of her testing various origin hypotheses and sorting out the paleontology, mineralogy and geochemistry.


Buckman, S.S. 1910. Certain Jurassic (Lias-Oolite) strata of south Dorset and their correlation. Quarterly Journal of the Geological Society 66: 52-89.

Burkhalter, R.M. 1995. Ooidal ironstones and ferruginous microbialites: origin and relation to sequence stratigraphy (Aalenian and Bajocian, Swiss Jura mountains). Sedimentology 42: 57-74.

Gatrall, M., Jenkyns, H.C. and Parsons, C.F. 1972. Limonitic concretions from the European Jurassic, with particular reference to the “snuff-boxes” of southern England. Sedimentology 18: 79-103.

Palmer, T.J. and Wilson, M.A. 1990. Growth of ferruginous oncoliths in the Bajocian (Middle Jurassic) of Europe. Terra Nova 2: 142-147.

Wooster Alumni in Iceland

June 29th, 2016

Hafnarfjörður, Iceland – Guest Blogger Ben Kumpf (’18)

There is never a dull moment in the life of a Wooster geologist. This afternoon at the Lava Hostel, Keck students were surprised with a visit from Brian S. Carl, Wooster alumni class of ’87. Brian, now a Senior Production Geologist for Shell, stopped by after hearing word from Dr. Wilson that Wooster students were in the area doing research. Brian and his wife Karen were enjoying their their vacation in Iceland; we just missed visiting with their daughter, Alena, who is a current Wooster student.

From left to right, Wooster alumni Karen Carl, Brian Carl, Meagen Pollock, and Ben Kumpf.

From left to right, Wooster alumni Karen Carl, Brian Carl, Meagen Pollock, and Ben Kumpf.

23 Hours of Sunlight and 22 Hours of Bugs (Part 1)

June 26th, 2016

Guest bloggers: Andrew Wayrynen and Jeff Gunderson


First attempt at collecting wood in Muir Inlet with Dan Lawson 

Two College of Wooster geologists in the Alaskan wilderness is always a recipe for success. Thanks to Dr. Wiles and the geo gang, we took our interests in glaciology and dendroclimatology to Glacier Bay National Park and Preserve in Southern Alaska, where scrambling up glaciers, maneuvering slippery alders, and finally sampling old growth trees became daily routine. As the first time in Alaska for Andrew and the second for Jeff, the beauty of the historic place was stunning and allowed scientific inquiry to flourish in its wake. Jeff’s tall task stood as “bridging the gap” of Glacier Bay’s glacial and climate history and Andrew, an English major by night, explored the location’s history in accordance with the writing of esteemed preservationist John Muir.

We were met by none other than Nick Wiesenberg at the Juneau airport, where we promptly sorted out food supplies and last minute gear checklists. After a few quick stops around town and a quiet night in the state’s capitol we were set to take off for Glacier Bay and to enter the field. We spent the night in a park-designated campsite and the next day we, as a trio, embarked a national park service boat to scoop up Dr. Wiles and his bright-eyed photographer Jesse who were already at Marble Mountain. Thereafter, we voyaged up-Bay to Muir Inlet where we set up camp between the Eastern-Arm’s McBride and Riggs Glaciers.


Carrying supplies in the sand dunes to cross the river and find the log


The older generation showing us how it’s done

The following day, the five of us kayaked to Wolf Lake in hopes of finding logs that would bridge the 2000-year old gap in the Glacier Bay tree-ring chronology. This totaled to a 14-mile round trip venture, where 6 miles were by foot and 8 were by kayak. The trek followed a decent sized creek, through marshy, bug-infested alders up a ridge to a drainage divide. From the top, a beautiful lake was visible whose crystal waters contained the remnants of an icy past. Down the other side of the divide was our goal- the roaring braided streams and the encasing alluvial fans. The mosquitoes brandished whatever the hell it is that they so eagerly stab us with and we set forth, mesh bug nets swaying in the wind, serving as a sort of lifeline. At last in the outwash plain, we spread out and surveyed the area for the missing pieces to our chronological puzzle. Our efforts proved fruitful, for there was more wood than we could conceivably carry.


A teachable moment for us in the field

5.5We’re considering making a show called Alaskan Bushwhackers

This first day of fieldwork truly set the tone for the remainder of the project. Sunny skies would subsequently outweigh threatening thunderous clouds, and complacency would never overcome hard work. The following afternoon the crew seized the opportunity to explore McBride Glacier by sea kayak, both resting tired legs and experiencing the immensity of one of the only remaining tidewater glaciers left in the Bay. We found it incredibly rewarding and inspiring to be so close to the very living beings that we have, and indeed will continue to, spend so much time studying. That afternoon, ice appeared the most brilliant shade of blue. Later that night, rice and beans never tasted so good.


Glaciers make us smile… stay posted for part 2


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