Wooster Geologist in Arizona

mpollock October 14, 2012 9:59 pm

ARIZONA – This Wooster Geologist has exchanged Ohio’s cool fall weather for blue skies and sunshine in Arizona. I’m here for a conference on Volcanism in the American Southwest, but I thought I’d come out early to explore some of Arizona’s geological wonders. My first stop was near the airport at Papago Park.

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Papago Park hosts the Phoenix Zoo, the Desert Botanical Garden, and several striking erosional landforms. The panoramic image below, from Pewe et al. (1986), shows the famous Hole in the Rock, Barnes Butte, and Contact Hill.

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According to Pewe et al. (1986), Papago Park is a pediment, or a gently sloping erosional surface that typically consists of bedrock with a thin sedimentary cover.

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Barnes Butte and Hole in the Rock are remnants of mid-Tertiary alluvial fan deposits that unconformably overlie Precambrian granite (Pewe et al., 1986).

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They consist of arkosic breccias with large clasts of granite and quartz in a red, sandy matrix (Pewe et al, 1986).

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My second stop was on the way to Flagstaff at Montezuma Castle National Monument.

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Although the name suggests this archaeological site was built by the Aztecs, this pueblo ruin was actually built by the Sinagua people in the early 1100s.

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This impressive 5-story building was constructed in a recess of the limestone cliffs overlooking Beaver Creek.

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On a day like today, with fantastic weather and a scenic view, I can understand why the Sinagua people decided to stay for a while. I lingered as long as I could, but I had to make it to Flagstaff today. I’ll be taking day trips out of Flagstaff until the conference starts, so stay tuned for more stories about Arizona’s geological playground.

References:
Pewe, T.L., C.S. Wellendorf, and J.T. Bales, (1986) Geologic cross sections of Papago Park pediment, Tempe quadrangle, Maricopa County, Arizona, AZ Bureau of Geology and Mineral Technology, Geological Investigation Series Map GI-2-C.

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Wooster’s Fossil of the Week: A spiriferid brachiopod (Middle Devonian of northwestern Ohio)

Mark Wilson October 14, 2012 1:39 am

I begin my Invertebrate Paleontology course by giving each student a common fossil to identify “by any means necessary”. This year I gave everyone a gray little brachiopod, one of which is shown above. They did pretty well. Kevin Silver (’13) got it down to the genus quickly. Turns out a Google image search on “common fossil” is very effective!

This is Mucrospirifer mucronatus (Conrad, 1841), a beautiful spiriferid brachiopod from the Silica Shale Formation (Middle Devonian) of Paulding County, northwestern Ohio. I collected it and many others at a quarry on a crisp October day with my friend and amateur paleontological colleague Brian Bade.

The image at the head of this page is a view of the dorsal valve exterior of Mucrospirifer mucronatus; the image immediately above is the ventral valve exterior. Spiriferid brachiopods like this are characterized by extended “wings” and a long hingeline. Inside was their defining feature: a spiral brachidium that held a delicate tentacular feeding device known as the lophophore.

This is the anterior of our brachiopod. The fold in the middle helped keep incurrent and excurrent flows separate, enabling more efficient filter-feeding. (By the way, have you noted the quirky asymmetry of this specimen?)

A view of the quarry that yielded our Fossil of the Week. Note the happy amateurs picking through blast piles of the Silica Shale Formation (Middle Devonian).

A pond in the quarry. It has an unexpected beauty, muddy as it is.

Timothy Abbott Conrad (1803-1877) described Mucrospirifer mucronatus in 1841. We met him before when discussing a siliquariid gastropod. He was a paleontologist in New York and New Jersey, and a paleontological consultant to the Smithsonian Institution.

Reference:

Tillman, J.R. 1964. Variation in species of Mucrospirifer from Middle Devonian rocks of Michigan, Ontario, and Ohio. Journal of Paleontology 38: 952-964.

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Wooster’s Fossils of the Week: Giant ostracods (Silurian of Estonia)

Mark Wilson October 7, 2012 1:24 am

During our Estonian expedition this summer, Richa Ekka (’13) chose as her Independent Study project focus the Soeginina Beds (lowermost Ludlow, Upper Silurian) of the Paadla Formation exposed in southeastern Saaremaa Island. These carbonate sediments, mostly dolomitized, were deposited in very shallow conditions — so shallow that in some places we have syneresis cracks and halite crystal molds. I expected the fossils to be mostly stromatolites and rare traces. We were pleasantly surprised to also find, though, a bed with numerous valves of the giant ostracod Herrmannina Kegel 1933 (shown above). I should have guessed that the hardy and extraordinarily successful ostracods would have been present.

At first we thought that these slightly-recrystallized shells must be bivalves (clams) because of their relatively large size (up to 25 mm long). But we didn’t see the typical bivalve muscle scars or hinging teeth and sockets. They had to be ostracods — but so big? The typical ostracod valve, shown below, is two mm or less in length. These Silurian examples are over 10 times that size. It would be like me meeting my 60-foot equivalent. Turns out that Herrmannina is known for its gigantism in the ostracod world — and it is not even the largest.

Cyamocytheridea sp. from the Eocene of Nederokkerzeel, Belgium. (Public Domain, Wikimedia.) This is the typical small size for an ostracod.
Today the ostracods, members of the Phylum Arthropoda, have over 8000 living species in both fresh and marine waters. Most crawl or burrow into sediments (that is, most are vagrant benthic epifaunal and infaunal), and a few are suspended in the water column (planktic). They have a wide range of feeding habits, from filter-feeding and deposit-feeding to herbivory and carnivory. (This is a key to their survival from the Early Paleozoic to today.) The living ostracod above shows that they are essentially a large head with several pairs of appendages inside two hinged valves. (The image is public domain from Anna33 at Wikipedia.) Their sex life is astonishing: ostracods have the largest sperm of any animals in both relative and absolute measures. Ostracod sperm are often ten times the length of the male body. (No, I don’t know how that works!)

Herrmannina is in the Order Leperditicopida of the Class Ostracoda. This genus was named in 1933 by Wilhelm Kegel (1890-1971), a geologist in the Preussische Geologische Landesanstalt of Berlin, Germany, who specialized in the Devonian and Carboniferous systems. I couldn’t find out much more about Dr. Kegel, but did stumble across an uncredited, undated low-resolution photo of him above. A fuzzy face from our paleontological past!

References:

Abushik, A. 2000. Silurian-earliest Devonian ostracode biostratigraphy of the Timan-Northern Ural Region. Proceedings of the Estonian Academy of Sciences, Geology 49: 112-125.

Belak, R. 1977. Ontogeny of the Devonian Leperditiid ostracode Herrmannina alta. Journal of Paleontology 51: 943-952.

Kegel, W. 1933. Zur Kenntnis palaozoischer Ostrakoden 3, Leperditiidae aus dem Mitteldevon des Rheinischen Schiefergebirges. Preussischen Geologischen Landesanstalt, Jahrbuch fur das Jahr 1932, Bd. 53, p. 907-935.

Kesling, R.V. 1958. A new and unusual species of the ostracod genus Herrmannina from the Middle Silurian Hendricks Dolomite of Michigan. Contributions, Museum of Paleontology, The University of Michigan 14, No. 9: 143-148.

Putzer, H. 1971. Wilhelm Kegel. Geologisches Jahrbuch 89: xiii-xxii.

Vannier,J., Wang, S.Q., and Coen, M. 2001. Leperditicopid arthropods (Ordovician – Late Devonian): Functional morphology and ecological range. Journal of Paleontology 75: 75-95.

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Wooster Geologist at the New England Aquarium

Mark Wilson October 4, 2012 4:17 pm

BOSTON, MASSACHUSETTS–I’m in Boston for a day on some College business and had the opportunity to visit the New England Aquarium. Its primary feature, a huge central aquarium with steps surrounding it, is under construction, but there were plenty of other exhibits to enjoy. I thought I’d post some images of organisms my Invertebrate Paleontology students would appreciate. The photo above, for example is of Olindias formosa — the Flower Hat Jelly. Wooster Paleontologists will immediately know it is a member of the Class Scyphozoa, and a pretty one at that.

The eight pinnate tentacles on each polyp here show that these are octocorals.

This was supposed to be a nice photo of green sea anemones, but I got photo-bombed by a fish!

This regular sea urchin is clinging to the glass with its tube feet. You can just make out the white jaws of the Aristotle’s Lantern.

Finally, this seadragon, with its wonderfully elaborate camouflage, has to make the show, even if it is a member of the Subphylum Vertebrata.

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Early Morning Powdering Session

mpollock October 2, 2012 9:14 am

WOOSTER, OH – Our dedicated Mineralogy students appeared in the lab bright and early this morning for an optional sample prep session.

Wide-eyed and alert in the early morning hours, the Mineralogy students are diligently powdering their samples for XRD analysis.

Each student has an unknown mineral that they are studying in a semester-long research project. Most of the work involves using modern analytical techniques for identification. Not all samples are well-suited for every technique, though. All of the students have been able to describe the physical properties of their sample, but only some can observe the crystallography. Some students are starting to use optical methods while others are using the XRD. Eventually, a few students will get to analyze the chemistry of their samples by XRF.

As with any research project, some students are struggling with uncertainty: “how am I supposed to be sure about the identification of my mineral?” That’s a fantastic question, and one that we are constantly engaging in our I.S. program. The answer is that the best identification is the one that is supported by the evidence. By using a variety of techniques, the students should become more confident in their identifications. Instantly, students see the advantages of some methods. In fact, one student asked if it was “cheating” to use the XRD to identify his/her mineral. No, it’s not cheating. It’s called data.

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Wooster’s Fossils of the Week: Beautiful molds on a concretion (Lower Carboniferous of Ohio)

Mark Wilson September 30, 2012 1:41 am

Kit Price (’13) was exploring a local creek on a Geomorphology course field trip north of Wooster led by Dr. Greg Wiles. Like the excellent paleontologist Kit is, her eyes continually searched the pebbles, cobbles, slabs and outcrops for that distinctive outline of something fossilian. This particular place has been in the blog before, so we know the stratigraphic and geological context of the rocks. Kit saw the curious golden brown, rounded rock above and immediately noted the presence of several fossils on its exterior. She collected it, cleaned it up, and the two of us examined the treasures.

Here is the key to what we found: A = trilobite pygidium external mold (more on this below); B = productid brachiopod dorsal valve internal mold; C = replaced bivalve shell fragment; D = productid brachiopod ventral valve external mold; E = nautiloid external mold. There are also external molds of twiggy bryozoans on the surface, but they are too small to distinguish in this view.

This rock is an ironstone concretion formed within the Meadville Member of the Cuyahoga Formation (Kinderhookian; Lower Carboniferous). It weathered out of the softer shale matrix and lay free on the creek bed. The original shells of the various fossils were dissolved away after burial, either being replaced with iron oxides (like the bivalve) or just remaining as open cavities (the molds). They represent a little survey of some of the animals that lived in this shallow, muddy seaway. Most of these fossils would have been lost to the dissolution, but the hard concretion preserved them.

The most interesting fossil here is the external mold of the trilobite pygidium (or tail piece). We don’t see these very often in Carboniferous and later rocks. The group is dwindling in advance of their final extinction at the end of the Permian period. I suspect this is the pygidium of Brachymetopus nodosus Wilson, 1979. I can only guess this, though, because only the cephalon (or head) of B. nodosus was described originally from the Meadville Member. This may be the long-missing pygidium of that species. It certainly has the little bumps that we would expect. (By the way, if you stare at the above image long enough, it appears in positive relief rather than the actual negative relief (or hole) that it is. It “pops out”, giving a view of what it may have looked like in life.)

Thanks, Kit, for such a nice view of a local Carboniferous community! It also brought back fond memories of my own local explorations as a Wooster student long, long ago.

References:

Corbett, R.G. and Manner, B.G. 1988. Geology and habitats of the Cuyahoga Valley National Recreation Area, Ohio. Ohio Journal of Science 88: 40-47.

Wilson, M.A. 1979. A new species of the trilobite Brachymetopus from the Cuyahoga Formation (Lower Mississippian) of northeastern Ohio. Journal of Paleontology 53: 221-223.

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Wooster’s Earthquake Machine

mpollock September 27, 2012 1:45 pm

WOOSTER, OH – Thanks to our crafty technician, the Wooster Geology Department is now the proud owner of an earthquake machine. The design comes from IRIS as a way to demonstrate Elastic Rebound Theory, the idea that stress accumulates on a fault until it slips, releasing the stress and causing an earthquake.

A view down the length of the earthquake machine.

The machine is relatively simple. It consists of a wooden block covered in sandpaper sitting on a sandpaper-covered track. The wooden block is attached to a rubber band, which is joined to a string on the other side. The crank at the end winds the string around the threaded rod, pulling the wooden block along the track.

A close-up view of the rubber band that joins the wooden block to the string.

In the experiment, a person turns the crank at a constant rate. The string pulls on the block, but the block doesn’t move. Initially, the rubber band stretches to accommodate the stress. Eventually, the stress overcomes the frictional force holding the wooden block in place. The wooden block jumps forward along the track and the rubber band returns to its original length. The stick-slip motion of the wooden block simulates the stick-slip motion of faults.

The brave volunteers who operated the earthquake machine and generated our first dataset.

After some practice and coordinated teamwork, we generated about 35 slip events. We recorded the position of the block after each event and the amount of time between events. It took about 20 minutes of class time, 8 volunteers, and 3 trial runs.

Although the model is relatively simple, the data are not. We’re using the data to ask sophisticated questions about earthquakes: What is the relationship between earthquake size and the amount of time between events? How predictable are earthquakes? What size earthquakes are most common? How do our results compare to the public perception of earthquakes? Eventually, we’ll compare our model to real earthquake data and case studies.

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TREE CAMPUS USA – The College of Wooster

gwiles September 24, 2012 6:59 am

On a beautiful homecoming afternoon in September – The College of Wooster celebrated its new designation as a Tree Campus USA. This special designation of The College of Wooster was lead by Beau Mastrine, director of grounds (above).  Partners include the City of Wooster and the OARDC. Grace Tompos, a good friend of the campus trees, places a shovel of dirt onto the latest maple planted in front of Holden Hall.
Andy Nash and Lauren Vargo of the Wooster Tree Ring Lab in Geology  explain the science of tree-rings as part of  the Tree Campus USA celebration. Both students will be using the campus tree-ring data in their drought studies and will be presenting their results at the annual meeting of the Geological Society of America Meeting in November. Andy’s work examines drought in the Midwest and Lauren’s study will analyze the link between North Pacific climate and Midwest drought.

Dr. Mariola (Environmental Studies) explains how he uses the campus trees in his courses. The tree journal assignment increases awareness of the practical and aesthetic value of the trees.

 

 

 

 

 

 

The D-shaped hole of the emerald ash borer (above). On the left is a “tree IV” (left) hooked up to a Green Ash on campus. This treatment repels the ash borer attack and protects the tree.

 

 

 

Employees of the City of Wooster explain the value and care of the urban forest.

Below is one of the bottom lines of the value of trees – here summarizing the value of the campus’ maples.

 

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Wooster’s Fossil of the Week: a deformed brachiopod (Upper Ordovician of Indiana)

Mark Wilson September 23, 2012 1:12 am

Kevin Silver (’13), a sharp-eyed paleontology student, found this odd brachiopod on our field trip earlier this month in southeastern Indiana. It comes from the Upper Ordovician (Katian) Whitewater Formation. Kevin correctly identified it as Vinlandostrophia acutilirata (Conrad, 1842), an orthid brachiopod formerly in the genus Platystrophia (see Zuykov and Harper, 2007). The above view is looking at the anterior of the brachiopod with the dorsal valve above and the ventral valve below.

What we see right away is that this brachiopod specimen is asymmetric: the right side is much shorter than the left. This is a feature of this individual, not the species. Is it a teratology — a deformity of growth? Probably. It is unlikely to be from post-depositional squeezing because the shell is otherwise in excellent shape. The oddity did not seem to hinder this individual from growing to a full adult size.

The same specimen looking at the dorsal valve with the hinge at the top of the image. The fold in the center is coming up towards us.

The posterior of our specimen, with the dorsal valve at the top. This is the hinge of the brachiopod.

A view of the ventral valve with the sulcus in the center.

(The above images are to help my paleontology students with their brachiopod morphology!)

References:

Alberstadt, L.P. 1979. The brachiopod genus Platystrophia. United States Geological Survey Professional Paper 1066-B: 1-20.

Boucot A.J. and Sun, Y.L. 1998. Teratology, possible pathologic conditions in fossil articulate brachiopods: p. 506-513, Collected works of the international symposium on Geological Sciences, Peking.

Conrad, T.A. 1842. Observations on the Silurian and Devonian Systems of the United States, with descriptions of new organic remains. Journal of the Academy of Natural Sciences of Philadelphia 8: 228-280.

Zuykov, M.A. and Harper, D.A.T. 2007. Platystrophia (Orthida) and new related Ordovician and Early Silurian brachiopod genera. Estonian Journal of Earth Sciences 56: 11-34.

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Wooster’s Fossils of the Week: a little sclerobiont community (Upper Ordovician of Indiana)

Mark Wilson September 16, 2012 1:28 am

Last week the students of my Invertebrate Paleontology class found many excellent fossils in the Whitewater and Liberty Formations of southeastern Indiana. We will be featuring some of them in this space. I want to start with one of my own finds: an orthid brachiopod from the Whitewater known as Vinlandostrophia acutilirata (Conrad, 1842), the inside of which is encrusted by old friends Cuffeyella arachnoidea (Hall, 1847) and Cornulites flexuosus (Hall 1847).

A sclerobiont is an organism living in or on a hard substrate. The branching form in the image is Cuffeyella arachnoidea, an encrusting cyclostome bryozoan well represented in the Cincinnatian Group (Taylor and Wilson, 1996). The conical encrusters are the lophophorate Cornulites flexuosus, a species we covered earlier in detail.

These sclerobionts were well protected from weathering on the outcrop by the concavity of the brachiopod’s interior, giving us a beautiful vignette of an ancient ecosystem.

References:

Conrad, T.A. 1842. Observations on the Silurian and Devonian Systems of the United States, with descriptions of new organic remains. Journal of the Academy of Natural Sciences of Philadelphia 8: 228-280.

Hall, J. 1847. Paleontology of New York, v. 1: Albany, State of New York, 338 p.

Taylor, P.D. and Wilson, M.A. 1996. Cuffeyella, a new bryozoan genus from the Late Ordovician of North America, and its bearing on the origin of the post-Paleozoic cyclostomates, p. 351-360. In: Gordon, D.P., A.M. Smith and J.A. Grant-Mackie (eds.), Bryozoans in Space and Time. Proceedings of the 10th International Bryozoology Conference, Wellington, New Zealand, 1995. National Institute of Water & Atmospheric Research Ltd, Wellington, 442 pages.

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