Archive for September, 2012

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

September 30th, 2012

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.

Wooster’s Earthquake Machine

September 27th, 2012

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.

TREE CAMPUS USA – The College of Wooster

September 24th, 2012

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.

 

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

September 23rd, 2012

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.

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

September 16th, 2012

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.

Paleontology field trip in southeastern Indiana

September 9th, 2012

RICHMOND, INDIANA–Geology students in the Cincinnati area are a bit spoiled when it comes to finding fossils in the field. The Upper Ordovician rocks here are world-famous for the extraordinary abundance, variety and preservation of invertebrate fossils.like those shown above and below.

Today Wooster’s Invertebrate Paleontology class had its annual field trip to collect specimens for lab projects and analyses. We traveled to roadcut outcrops south of Richmond, Indiana — places Wooster Geologists have been visiting for about 30 years. Most recently Kit Price (’13) and her team was here collecting specimens for her Independent Study project. She was on this trip as well, and the class found lots of goodies for her work.

Our fleet of vehicles at our first outcrop (the Whitewater Formation).

Matt Peppers (’13) and Will Cary (’13) striking a Team Utah pose with the Whitewater Formation. Note that this rock unit is mostly resistant limestone beds.

The outcrop of the Liberty Formation at our second stop. (The Liberty is known as the Dillsboro Formation in Indiana, but we tend to use the Ohio names just across the border.) Note the prominence of less resistant shale.

It was a great day — sunny, warm and full of fossils. This class was especially adept at finding unusual specimens, several of which will show up us Fossils of the Week!

Wooster’s Fossil of the Week: a twisted little crinoid (Lower Silurian of Estonia)

September 9th, 2012

This week’s fossil is a tiny little crinoid with an odd shape. Calceocrinus balticensis (shown above with the scale bar as one millimeter) is a new species from the Lower Silurian (Llandovery) of Hiiumaa, western Estonia. It is part of a series of new crinoid taxa described in the most recent issue of Acta Palaeontologica Polonica by Ausich et al. (2012). All that geological work in Estonia by Ohio State and Wooster geologists is resulting in several paleontological publications, all with the collaboration of our friend Olev Vinn at the University of Tartu, Estonia.

The western Estonian island of Hiiumaa where our little crinoid was found. (Image courtesy of Google Maps.)

Calceocrinus balticensis Ausich, Wilson and Vinn, 2012 (to give its full and glorious name) is unusual because its crown (the filter-feeding “head” of the crinoid) is recumbent on the column (the “stem”). In the images above you can see the column as a series of disks on their sides at the bottom of the view. The crown is the set of larger plates attached to the top of the column, from which there are several arms extending to the right. This new species is the first of its genus from the paleocontinent Baltica. It had sister species in North America on what became Anticosti Island in eastern Canada (see Ausich and Copper, 2010).

Calceocrinids (Order Calceocrinida Ausich, 1998) lived very close to the seafloor. The column of an individual, which in other crinoids holds the crown far off the substrate, lay horizontally along the bottom. The crown was hinged at its base so that it could be elevated perpendicular to the stem with the arms spread wide to filter organic material from the water. During non-feeding times the crown would lie inconspicuous on the bottom. This crinoid literally had a very low profile compared to its showy cousins.

Now, though, the shy little Calceocrinus balticensis gets a moment of exposure and formal admission to the roll call of life’s species.

References:

Ausich, W.I. 1998. Phylogeny of Arenig to Caradoc crinoids (Phylum Echinodermata) and suprageneric classification of the Crinoidea. The University of Kansas Paleontological Contributions, n.s. 9, 36 pp.

Ausich, W.I. and Copper, P. 2010. The Crinoidea of Anticosti Island, Québec  (Late Ordovician to Early Silurian). Palaeontographica Canadiana 29, 157 pp.

Ausich, W.I., Wilson, M.A. and Vinn, O. 2012. Crinoids from the Silurian of western Estonia. Acta Palaeontologica Polonica 57: 613-631.

Remember those wooden crystal models?

September 4th, 2012

WOOSTER, OH – I’m always awed by the beautiful and perfect symmetry of crystals. I can think of no better way to teach external symmetry than with wooden crystal models. The wooden crystal models are a common experience in geology, across generations and continents, although it seems they may be on the endangered list. I’ve chosen to continue using the models in Mineralogy because they allow students to see and “feel” the symmetry operations and our structural geologist thinks the blocks help students with their spatial reasoning skills.

Behold, the beautiful and mysterious crystal model.

Most people develop a love-hate relationship with the models, but I have to admit I’ve always been infatuated. They’re like logic puzzles with a million different secrets all wrapped up in what seems like a simple wooden block. Spend some time with the block and it will reveal a wealth of information.

This block has 5 mirrors, 1 four-fold rotation axis, and 4 two-fold rotation axes.

This combination of symmetry elements belongs to the point group (or crystal class) 4/m 2/m 2/m. In Hermann-Mauguin notation, 4/m refers to a four-fold rotation axis perpendicular to a mirror. The second and third 2/m terms refer to two-fold rotation axes that are perpendicular to mirrors, one set of axes that exits the crystal in the middle of the faces and another set of axes that exits the crystal on the edges.

The axes (a1, a2, and c) of the tetragonal crystal system align with symmetry elements. Some of the faces have been labeled with their Miller Indices.

The 4/m 2/m 2/m point group belongs to the tetragonal crystal system, which has three mutually perpendicular crystallographic axes. The two horizontal axes (a1 and a2) are equal in length and coincide with the two-fold rotation axes. The vertical axis (c) is longer than the horizontal axes and coincides with the four-fold rotation axis.

Once the crystallographic axes have been determined, we can describe the orientation of the crystal faces using Miller Indices. In short, Miller Indices consist of three numbers (four in the case of hexagonal crystals) that are derived from the intercepts of crystal faces. The crystal face that intersects the a1 axis but parallels the a2 and c axes is assigned a Miller Index of 100. The crystal face that never intersects a1 but cuts both a2 and c is assigned a Miller Index of 011.

We could keep going with this…describing forms, measuring angles, plotting on stereonets, but we won’t. Making it through Miller Indices this week will be enough for the Mineralogy students. Here’s the big secret: this is one of crystals we’re working on in class. I guess we’ll find out which students read the blog on a regular basis!

Wooster’s Fossils of the Week: Sea urchin bits (Middle Jurassic of southern Israel)

September 2nd, 2012

Our fossils this week come from our growing collection of material found in the Matmor Formation (Callovian-Oxfordian) of Makhtesh Gadol, southern Israel. In November I will be giving a talk at the annual meeting of the Geological Society of America in Charlotte, North Carolina, on the taphonomy of Matmor regular echinoids (“sea urchins”). The abstract is online. Taphonomy is the study of the fossilization process. In this case it is essentially what happened to the echinoid remains after death and before final burial. This part of the fossilization history can tell us much about the environment of deposition of the Matmor Formation. The image above is one of the rare complete tests (skeletons) in our study. It is probably a rhabdocidarid echinoid, but the preservation is not quite good enough to tell.

Echinoids are especially interesting for this kind of work. (That link will send you to a wonderful site explaining all you’ll want to know about echinoids and their evolutionary history.) They originated way back in the Ordovician Period, about 450 million years ago, and have retained the same general skeletal structure since then. Their response to physical and chemical conditions on the ocean floor has thus been consistent over time, and we can experiment with modern representatives to estimate their decay and disarticulation processes.

Typical test plate fragments from a rhabdocidarid echinoid in the Matmor Formation. The specimen on the right is encrusted by a very thin plicatulid bivalve, which is in turn encrusted by small branching stomatoporid bryozoans.

A flattened and thorny rhabdocidarid spine. The left end has a socket that attached to a tubercle (bump) on the test of the echinoid.

This cool spine was apparently bitten by a Jurassic fish! Wish I had at least one of that fish’s teeth.

The strange swollen sphere with little holes at the base of this echinoid is a cyst that likely formed from a copepod parasitic infection. Neat (and so far undescribed in the literature).

We can conclude that the Matmor Formation was deposited in very shallow, warm marine waters, probably lagoonal (a favorite living place for rhabdocidarid echinoids), that were only occasionally disturbed by storms and “burial events”. The echinoids decayed and disarticulated on the seafloor (a process that takes about a week) and the pieces tossed around for awhile gathering sclerobionts (encrusters, in this case) and experiencing significant abrasion. This matches other evidence from our previous paleontological studies of the Matmor’s depositional environment.

References:

Donovan, S.K., and Gordon, C.M., 1993, Echinoid taphonomy and the fossil record: Supporting evidence from the Plio-Pleistocene of the Caribbean. Palaios, v. 8, p. 304-306.

Greenstein, B.J., 1991, An integrated study of echinoid taphonomy: Predictions for the fossil record of four echinoid families: Palaios, v. 6, p. 519-540.

Greenstein, B.J., 1992, Taphonomic bias and the evolutionary history of the Family Cidaridae (Echinodermata: Echinoidea): Paleobiology, v. 18, p. 50-79.

Greenstein, B.J., 1993, Is the fossil record of the regular echinoid really so poor? A comparison of Recent and subfossil assemblages: Palaios, v. 8, p. 587-601.

Kidwell, S.M. and Baumiller, T., 1990, Experimental disintegration of regular echinoids: Roles of temperature, oxygen and decay thresholds: Paleobiology, v. 16, p. 247-271.