Wooster Geologist on the Blue Ridge of Virginia

mwilson June 3, 2012 8:13 pm

The summer field season has started for Wooster geologists. Greg Wiles is now in southern Alaska with his students doing dendrochronology and geomorphology. Meagen Pollock and Shelley Judge are running an integrated project in west-central Utah with their students doing structural geology, geochemistry, vulcanism and petrology. Watch these pages for their reports!

As for me, I’m on a short vacation. A geologically-rich vacation, of course! My wife Gloria and I are visiting the Shenandoah region of Virginia. We started today in Shenandoah National Park, driving south down Skyline Drive along the Blue Ridge. The weather is spectacular as you can tell from the above image. This is a view near Mile 61 looking west across the Valley and Ridge Province.
The Blue Ridge Province has a bedrock made of igneous and metamorphic Grenville basement rocks up to a billion years old. The Blue Ridge itself, which runs north-south from Pennsylvania to Georgia, is mostly an eroded anticline overturned westward. Directly west is the Valley and Ridge Province. In the image above, the “A” is at the spot where the top photograph was taken. You can easily pick out the physiographic and geological provinces.

Most of the rocks exposed along Skyline Drive in Shenandoah National Park are metabasalts of the Catoctin Formation (Ediacaran, about 570 million years old). A metabasalt is a basalt that has been metamorphosed (unsurprisingly). The original basalts of the Catoctin were erupted during the rifting open of the Iapetus Ocean, a precursor of the Atlantic. Many of these eruptions were on this early seafloor, forming pillows and thick flows. The total basalts in this formation piled up in layers to almost 800 meters thick.
The metabasalt of the Catoctin has a greenish color in many places, giving it the common name “greenstone”. Veins of green minerals, primarily epidote and chlorite, run through the rock, especially in the northern part of the Blue Ridge. This greenstone is occasionally mined to produced chemical-resistant lab surfaces and facing stones.

The dramatic geology was accompanied by beautiful wildflowers. The rocks, flowers, views and weather combined to make an extraordinary day of natural history. Tomorrow we’ll explore how this geology affected human history in very direct ways.

Aquilegia canadensis (Red Columbine).

Penstemon canescens (Hairy Beardtongue).

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Wooster’s Fossil of the Week: a very large clam (Upper Cretaceous of South Dakota, USA)

mwilson June 3, 2012 1:31 am

Our version above of the bivalve Inoceramus is actually rather small compared to how big it can get. The record holder is a specimen 187 centimeters in diameter (over six feet) in the Geological Museum of Copenhagen. This Wooster Inoceramus is from the Pierre Shale of South Dakota, a unit my colleague Paul Taylor and student John Sime once explored in some detail.

Inoceramus means “strong pot”, which I assume must refer to its unusually thick shell with calcite prisms oriented perpendicular to the surface. They also had concentric “wrinkles” that make them easily identifiable even in small fragments. In fact, we can even recognize the isolated prisms of inoceramids in thin-sections of sedimentary rocks. This genus was widespread during the Late Cretaceous, being found from British Columbia to Germany. The had very large gill systems that enabled them to live in poorly-oxygenated waters. It makes sense that they are so common in the dark, carbon-rich sediments of the Pierre Shale.
Inoceramus was named by the dapper James Sowerby (above) in 1814, so it is a genus we have known for a very long time. Sowerby (1757-1822) was an Englishman skilled in natural history as well as scientific illustration. He named the first species of the genus as Inoceramus cuvieri to honor the French scientist Georges Cuvier. His illustration of I. cuvieri is below.
Inoceramus was one of the first invertebrate fossils to be the subject of an evolutionary study in a modern way. Woods (1912) studied various species of Inoceramus in the Cretaceous, noting that it apparently underwent rapid intervals of change. My former student Colin Ozanne and his advisor (and my friend) Peter Harries studied Inoceramus and its relatives in the Western Interior Seaway. Their study, published in 2002, showed that inoceramids were greatly stressed by parasites and predators before their final extinction in the Maastrichtian.

References:

Ozanne, C.R and Harries, P.J. 2002. Role of predation and parasitism in the extinction of the inoceramid bivalves: an evaluation. Lethaia 35: 1–19.

Sowerby, J. 1822. On a fossil shell of a fibrous structure, the fragments of which occur abundantly in the chalk strata and in the flints accompanying it. Transactions of the Linnean Society of London XIII: 453-458. Plate XXV.

Woods, H. 1912. The evolution of Inoceramus in the Cretaceous Period. Quarterly Journal of the Geological Society 68: 1-20.

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Scovel Hall lecture room renovations begin (periodically updated)

mwilson May 31, 2012 3:42 pm

20120531-154554.jpg Our beloved Scovel Hall lecture rooms are finally being updated. The fixed seats in Room 105 endured by generations of student behinds are headed to the dumpster (including their 1985 color scheme) and will be replaced by tables and movable chairs. Seating capacity will go from the huge 83 to a more comfortable 50. The more flexible seating will allow us to move around more in the classroom. Scovel 205 upstairs is also being redone in a similar way.

I’ve taught in the present arrangement for 27 years. I’m anxious to teach in the new improved rooms!

Scovel Room 105 on June 6th with all seats removed.

Where those chairs and the carpet ended up!

 

The new carpet in Scovel 105 on July 31.

 

Scovel 105 in early August 2012.

First class in the new Scovel 100! (History of Life, 8:00 a.m., August 27, 2012)

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Wooster’s Fossil of the Week: a trilobite burrow (Upper Ordovician of Ohio)

mwilson May 27, 2012 1:43 am

This is one of my favorite trace fossils. Rusophycus pudicum Hall, 1852, is its formal name. It was made by a trilobite digging down into the seafloor sediment back during the Ordovician Period in what is now southern Ohio. It may have been hiding from a passing predator (maybe a eurypterid!), just taking a “rest” (what I learned in college), or maybe looking for worms to eat. (There is another example on this blog from the Cambrian of western Canada.)

Rusophycus is always the first trace fossil I introduce in the Invertebrate Paleontology course because it is simple in form and complex in interpretation. It shows that a relatively straightforward process (digging down with its two rows of legs) can have had several motivations. Rusophycus even shows that more than one kind of organism can make the same type of trace. Rusophycus is also found in the Triassic, long after trilobites went extinct. (These were likely made by horseshoe crabs.) It is also good for explaining the preservation of trace fossils. The specimen above is “convex hyporelief”, meaning it is on the bottom of the sedimentary bed and convex (sticking out rather than in). This is thus sediment that filled the open trilobite excavation.

Trilobites making Rusophycus (from http://www.geodz.com/deu/d/Trilobita).

James Hall (1811–1898) named Rusophycus pudicum in 1852. The image of him above is from shortly before his death (photograph credit: The American Monthly Review of Reviews, v. 18, 1898, by Albert Shaw). He was a legendary geologist, and the most prominent paleontologist of his time. He became the first state paleontologist of New York in 1841, and in 1893 he was appointed the New York state geologist. His most impressive legacy is the large number of fossil taxa he named and described, most in his Palaeontology of New York series.

James Hall is in my academic heritage. His advisor was Amos Eaton (1776-1842), a self-educated geologist (he learned it by reading in prison!). One of James Hall’s students was Charles Schuchert (1856-1942), a prominent invertebrate paleontologist. Schuchert had a student named Carl Owen Dunbar (1891-1979) — Schuchert and Dunbar were coauthors of a famous geology textbook. Dunbar had a student at Yale named William B.N. Berry (1931-2011), my doctoral advisor. Thus I feel an intellectual link to old man Hall above.

References:

Baldwin, C.T. 1977. Rusophycus morgati: an asaphid produced trace fossil from the Cambro-Ordovician of Brittany and Northwest Spain. Palaeontology 51: 411–425.

Donovan, S.K. 2010. Cruziana and Rusophycus: trace fossils produced by trilobites … in some cases? Lethaia 43: 283–284.

Hall, J., Simpson, G.B. and Clarke, J.M. 1852. Palaeontology of New York: Organic remains of the Lower Middle Division of the New-York System. C. Van Benthuysen, New York, 792 pages.

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Forbes lists Geology as 7th in its “15 Most Valuable College Majors”

mwilson May 26, 2012 12:59 pm

Sure it is intellectually stimulating, adventurous and fun, but geology is also an important field for the present and future according to the latest issue of Forbes magazine. Geology is ranked as number 7 in the most valuable college majors, with a starting median pay of $45,300 and a “mid-career” rise in pay of 84%. The projected job growth in geology is 19.3%.

Top image: Rob McConnell and Palmer Shonk in Estonia. Bottom image: Sophie Lehmann in England.

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Wooster’s Fossils of the Week: Corkscrew shells from the Pliocene of Cyprus

mwilson May 20, 2012 1:15 am

Steve Dornbos (’97), now a professor at the University of Wisconsin, Milwaukee, and I found these intricate shells by the hundreds in the Nicosia Formation (Pliocene) of Cyprus during his Independent Study field work. (We published this study in 1999.) They are the gastropod (snail) species Turritella tricarinata (Brocchi 1814).

Turritellid snails are still very common today, so we know quite a lot about their ecology and physiology. They are an unusual mix of deposit-feeder and filter-feeder, eating organic particles on the sediment surface and in the water. They do it by creating a current with cilia, drawing water into their mantle cavities. There they have a complex system of tentacles that filter out the largest particles, allowing only the small, digestible goodies onto the surfaces of their gills. The organics are coated with mucus and made into a kind of sticky string that is pulled into the mouth (Graham, 1938). These snails are usually found in large aggregations, just like what we found in the Pliocene of Cyprus.
Turritella tricarinata was originally described by Giovanni Battista Brocchi in 1814 as Turbo tricarinata. Brocchi (1772-1826) was an Italian natural historian who made significant contributions to botany, paleontology, mineralogy and general geology. He was born in Bassano del Grappa, Italy, and studied law at the University of Padova. He liked mineralogy and plants much better than lawyering, though, and became a professor in Brescia. His work resulted in an appointment as Inspector of Mines in the new kingdom of Italy.

Brocchi wrote the first thorough geological assessment of the Apennine Mountains, and he included in it a remarkable systematic study of Neogene fossils. He compared these fossils to modern animals in the Mediterranean — a very progressive thing to do at the time.
Above are drawings made by Brocchi of the turritellid fossils he found in the Apennines during his extensive study published in 1814. Note that in the Continental fashion still followed today, the shells are figured aperture-up. Americans and the rest of the English-speaking world orient them in the proper way.

Brocchi was an adventurous traveler, but it eventually did him in. He died in Khartoum in 1826, a “victim of the climate” and a martyr for field science.

References:

Brocchi, G.B. 1814. Conchiologia fossile subapennina con osservazioni geologiche sugli Apennini e sul suolo adiacente. Milano Vol. I: pp. LXXX + 56 + 240; Vol. II, p. 241-712, pl. 1-16.

Dornbos, S.Q. and Wilson, M.A. 1999. Paleoecology of a Pliocene coral reef in Cyprus: Recovery of a marine community from the Messinian Salinity Crisis. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 213: 103-118.

Graham, A. 1938. On a ciliary process of food-collecting in the gastropod Turritella communis Risso. Proceedings of the Zoological Society of London A108: 453–463.

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Wooster’s Fossils of the Week: Intricate networks of tiny holes (clionaid sponge borings)

mwilson May 13, 2012 1:28 am

The most effective agents of marine bioerosion today are among the simplest of animals: clionaid sponges. The traces they make in carbonate substrates are spherical chambers connected by short tunnels, as shown above in a modern example excavated in an oyster shell. The ichnogenus thus created is known as Entobia Bronn, 1838. I’ve become quite familiar with Entobia throughout its range from the Jurassic through the Recent (with an interesting early appearance in the Devonian; see Tapanila, 2006).
The holes in this Cretaceous oyster are the sponge boring Entobia; the cyclostome bryozoan is Voigtopora. This specimen is from the Coon Creek Beds of the Ripley Formation (Upper Cretaceous) near Blue Springs, Mississippi. (This specimen was collected during a 2010 Wooster/Natural History Museum expedition to the Cretaceous and Paleogene of the Deep South.)
This is a modern clam shell showing Entobia and several other hard substrate dwelling organisms (sclerobionts).
Entobia was named and first described by Heinrich Georg Bronn (1800-1862), a German geologist and paleontologist. He had a doctoral degree from the University of Heidelberg, where he then taught as a professor of natural history until his death. He was a visionary scientist who had some interesting pre-Darwinian ideas about life’s history.

References:

Bromley, R.G. 1970. Borings as trace fossils and Entobia cretacea Portlock, as an example. Geological Journal, Special Issue 3: 49–90.

Bronn, H.G. 1834-1838. Lethaea Geognostica (2 vols., Stuttgart).

Tapanila, L. 2006. Devonian Entobia borings from Nevada, with a revision of Topsentopsis. Journal of Paleontology 80: 760–767.

Taylor, P.D. and Wilson, M.A. 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1-103.

Wilson, M.A. 2007. Macroborings and the evolution of bioerosion, p. 356-367. In: Miller, W. III (ed.), Trace Fossils: Concepts, Problems, Prospects. Elsevier, Amsterdam, 611 pages.

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Theory to Practice: An Early GSA Abstract

mpollock May 11, 2012 10:15 am

This semester, I’ve had the pleasure of teaching a special topics lab course in geochemistry. Given our new lab facilities, I decided to approach the class as an analytical geochemistry course. We explored sampling strategies, data quality, and the theory and techniques behind X-ray methods (XRF), electron-beam methods (SEM-EDS), and mass spectroscopy methods (ICP-MS).  Unlike a typical survey course, our course was entirely research-based. We actually became analytical geochemists by conducting an authentic research project on a suite of Icelandic basalts. Our goal was to investigate the development of a structural basin in northern Iceland by interpreting the petrogenesis of lavas that were erupted during different phases of basin construction. This week, we’ve accomplished our goal and have written an abstract to submit to the Fall 2012 meeting of GSA.

Here is the text of the abstract:

A GEOCHEMICAL ANALYSIS OF THE VATNSDALFJALL STRUCTURAL BASIN, SKAGI PENINSULA, NORTHWEST ICELAND

Matthew Peppers, Sarah Appleton, Lindsey Bowman, Andrew Collins, Whitney Sims, Melissa Torma, Meagen Pollock

Vatnsdalfjall, in northwest Iceland, exposes the upper ~700 m of crust formed ~7 Ma ago at the extinct Hunafloi-Skagi rift zone. In general, the lava flows dip gently westward toward the abandoned rift axis, but are interrupted by a local area of steeply dipping lava flows known as the Vatnsdalur Structural Basin (VSB). The VSB is composed of three sequences of lava flows emplaced before, during, and after subsidence. Using the geochemistry (XRF, ICP-MS) of samples gathered in the field in 2006 and 2007 and previous data from Ackerly (2004) and McClanahan (2004), we were able to establish a basic eruptive history for the sequences. Major element analysis shows diverse rock types, including basalt, basaltic andesite, dacite, and rhyolite. Sequence 1 shows the greatest diversity and was primarily affected by mineral accumulation, while Sequences 2, 3, and the dikes follow the trend of a shallow level fractional crystallization model based on a modified parent magma from Sequence 1. Trace element ratios suggest the presence of 1 (or 2) parent magmas, although the intermediate to silicic lavas appear to be generated by a separate process. Sequence 1 contains various lava flows, each with a uniform thickness, emplaced on relatively flat terrain. Sequence 2 was emplaced on top of Sequence 1 as subsidence of the basin was occurring, creating lava flows that thicken toward the basin interior. Intermediate to silicic rocks are absent during this interval and dikes cut Sequence 1 to feed lavas in Sequence 2. After a period of erosion, Sequence 3 was erupted above Sequence 2. Dikes that feed Sequence 3 cut through Sequence 2. The development of the VSB may have been associated with a waning period in the magmatic system, where magmas cooled and evolved (following an evolutionary trend controlled by fractional crystallization) and there was little partial melting of the crust (given the lack of intermediate to silicic lavas).

And some key figures:

Geologic map that shows the location of our samples on Sequence 1 (green), Sequence 2 (pink), and Sequence 3 (blue).

CaO vs. MgO (wt%). Symbols for dikes and Sequences 1, 2, and 3 are as shown on the geologic map. Previous data outlined by the dashed line. Fractional crystallization model shown by the black like. Arrows indicate effects of mineral accumulation. Plagioclase (pentagons) and clinopyroxene (stars) are also shown.

Schematic model (not to scale) for the development of the basin.

I applaud all of the students for their excellent work. They really took ownership of this project and deserve all of the credit. Look for us at GSA in the fall!

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Behind the Scenes at the Smithsonian

mpollock May 9, 2012 10:15 am

WASHINGTON, D.C. – Guest blogger: Lindsey Bowman (’12). As part of CUR’s Posters on the Hill event, we took a behind-the-scenes tour of the U.S. National Meteorite Collection at the Smithsonian. Our host was Dr. Cari Corrigan.

Dr. Corrigan showed us meteorites from the asteroid belt.

This is an Fe-Ni meteorite. The pink and blue colors are a reflection, but the green areas are olivine crystals.

This core of an iron meteorite has been etched with nitric acid to reveal the widmanstatten pattern. The dark spots are iron sulfide inclusions.

This is the famous Allende carbonaceous chondrite.

Next, we toured the Entomology Collections with USDA Entomologist Dr. John Brown, whose specialty is Lepidoptera (moths and butterflies).

We started on the 7th floor of the building at a cabinet labeled "Oh My!" where he showed us jaw-dropping, giant, colorful bugs.

Dr. Brown then took us to the "ugly little brown moths" that are the focus of his research. They feed on kiwi and avocado crops.

Finally, Dr. Brown showed us bright blue butterflies. The color of these butterflies won't fade over time because it's a structural optical feature of their wings.

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Presentations on Capitol Hill

mpollock May 7, 2012 8:42 pm

WASHINGTON, D.C. – Students and faculty aren’t the only audiences for Wooster I.S. presentations. This year, two Wooster students were selected (out of 850 applicants) to represent the best in undergraduate research at CUR’s Posters on the Hill event. Congratulations to Lindsey Bowman (’12) and Nikolai Radzinski (’13) on their accomplishment! Be sure to check out the press release to hear about their experiences in their own words.

 

Lindsey's research took center stage as she was interviewed by the camera crew.

 

Lindsey presented her I.S. research on subglacial eruptions.

 

Nikolai, a junior biochemistry major, presented his summer research on measuring motor function loss for brain injury victims.

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