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mpollock 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
Mark Wilson July 1st, 2016
These 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.
This 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.
We’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.
There are also cyclostome bryozoans embedded within the iron-oxide layers, as shown in this image from Palmer and Wilson (1990, fig. 3).
We 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.
Paul 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).
Sometimes the plates look like they’ve partially evaporated, leaving remnants that resemble Hebrew letters!
Associated 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.
mpollock 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.
gwiles 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
We’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
mpollock June 26th, 2016
Hafnafjörður, Iceland – Cara Lembo (Amherst), official Keck Iceland 2016 Guest Blogger.
Greetings from rainy Iceland! After spending 4 full days in the field we are spending a rainy day inside discussing projects and compiling our data.
We spent our first day and a half in Iceland inside the Undirhlíðar quarry – an ideal place to observe cross sections of pillow lavas and other volcanic deposits.
After getting a feel for many different types volcanic deposits in the quarry, we headed out to survey the ridge South of the quarry and observe these deposits “in the wild.”
We surveyed the ridge for the next day and a half. Highlights include discovering an unexpected tephra cone and learning how to tell the difference between goats and sheep. According to Ben you say, “Goaty, Goaty raise your tail!”
Once we surveyed the whole ridge, we started our mapping project with a gully on the southwest side of the ridge.
We’ve also sampled some local Icelandic cuisine such as Skyr, chocolate covered licorice and, to Dr. Pollock’s dismay, Harðfiskur (dried fish).
Overall it has been an exciting first week in the field. More to come as we continue working in the field and trying to adjust to the never-ending daylight.
Wooster’s Fossils of the Week: Encrusting cyanobacteria from the Upper Ordovician of the Cincinnati region
Mark Wilson June 24th, 2016
Deep in the basement of the Natural History Museum in London, Paul Taylor and I were examining cyclostome bryozoans encrusting an Upper Ordovician brachiopod with a Scanning Electron Microscope (SEM). This is one of our favorite activities, as the SEM always reveals tiny surprises about our specimens. That day the surprises were the smallest yet – fossils we had never seen before.
We were studying the dorsal exterior surface of this beat-up brachiopod from a 19th Century collection labelled “Cincinnati Group”. (Image by Harry Taylor.) We knew it was the strophomenid Rafinesquina ponderosa, and that the tiny chains of bryozoans encrusting it were of the species Corynotrypa inflata. We’ve seen this scene a thousand times. But when we positioned the SEM beam near the center of the shell where there was a brown film …
In some places there were thick, intertwining mats of these squiggles. We later found these fossils on two other brachiopod specimens, both also Rafinesquina ponderosa and from 19th Century collections with no further locality or stratigraphic information.
Last week Paul and I scanned these specimens again and began to put together an analysis. We believe these are fossil cyanobacteria. They are uniserial, unbranching strands of cells that range from 5 to 9 microns in length and width. Some of individual strands are up to 700 microns long and many are sinuous. The cells are uniform in size and shape along the strands; there are no apparent heterocysts. They appear very similar in form to members of the Order Oscillatoriales.
Cyanobacteria are among the oldest forms of life, dating back at least 2.1 billion years, and they are still abundant today. The fossils are nearly identical to extant forms, as seen above (image from: http://www.hfmagazineonline.com/cyanobacteria-worlds-smallest-oldest-eyeball/).
Paul made this remarkable image, at 9000x his personal record for high magnification, showing the reticulate structure preserved on some of the fossil surfaces. Note that the scale bar is just 2 microns long. These are beautiful fossils in their tiny, tiny ways.
We have not seen these cyanobacteria fossils before on shell surfaces, so we submitted an abstract describing them for the Geological Society of America annual meeting in Denver this September. We are, of course, not experts on bacteria, so we are offering our observations to the scientific community for further discussion. Here is the conclusion of our abstract —
“We suggest the cyanobacterial mats developed shortly before final burial of the brachiopod shells. Since the cyanobacteria were photosynthetic, the shells are inferred to have rested with their dorsal valve exteriors upwards in the photic zone. That Cincinnatian brachiopod shells were occupied by cyanobacteria has been previously well demonstrated by their microborings but this is the first direct evidence of surface microbial mats on the shells. The mats no doubt played a role in the paleoecology of the sclerobiont communities on the brachiopods, and they may have influenced preservation of the shell surfaces by the “death mask” effect. The pyritized cyanobacteria can be detected with a handlens by dark squiggles on the brachiopod shells, but must be confirmed with SEM. We encourage researchers to examine the surfaces of shells from the Cincinnatian and elsewhere to find additional evidence of fossilized bacterial mats.”
Noffke, N., Decho, A.W. and Stoodle, P. 2013. Slime through time: the fossil record of prokaryote evolution. Palaios 28: 1-5.
Tomescu, A. M., Klymiuk, A.A., Matsunaga, K.K., Bippus, A.C. and Shelton, G.W. 2016. Microbes and the Fossil Record: Selected Topics in Paleomicrobiology. In: Their World: A Diversity of Microbial Environments (pp. 69-169). Springer International Publishing.
Vogel, K. and Brett, C.E. 2009. Record of microendoliths in different facies of the Upper Ordovician in the Cincinnati Arch region USA: the early history of light-related microendolithic zonation. Palaeogeography, Palaeoclimatology, Palaeoecology 281: 1-24.
mpollock June 21st, 2016
Hafnafjörður, Iceland – What a fantastic day! Dr. Ben Edwards and I are leading a 6-student Keck trip to Iceland to study a glaciovolcanic ridge. It was a long travel day, but everyone (and their luggage) arrived safe and sound. No need to waste any time – soon after we set up camp, we headed to the field.
A beautiful day welcomed us to our field site, but we couldn’t stay for too long because we had a birthday to celebrate. Today’s introduction was brief, but we’ll continue to post about our work and adventures over the next month.