Archive for January, 2011

Wooster’s Fossil of the Week: The Multidisciplinary European Thorny Oyster (Pliocene of Cyprus)

January 30th, 2011

In the summer of 1996, I was a co-director of  a Keck Geology Consortium project on the island of Cyprus. My students and I worked on the hot central plains far from the well known ophiolite complex in the cool mountains. One day Wooster student Steve Dornbos and I stumbled across a fantastic coral reef weathering out of Pliocene silts and clays. (Check out the locality on Google Maps at N35° 5.767′, E33° 8.925′. We weren’t far from the UN Buffer Zone between us and the “Turkish Cypriot political entity” to the north.) Describing this fossil reef and its associated organisms, and interpreting it as a recovery fauna after the Messinian Salinity Crisis, became the basis of Steve’s Independent Study. I like to think it is what made him the famous paleontologist he is today.

The reef framework was made by the scleractinian coral Cladocora, and there was a wonderful diversity of other organisms preserved in and on its branches. (You can read our paper about the reef by downloading this pdf: Dornbos & Wilson, 1999.) One of the most spectacular is shown above: the European Thorny Oyster Spondylus gaederopus Linnaeus 1758. This filter-feeding pectinoid bivalve (not a true oyster) cemented itself to the coral and then filtered the surrounding water for nutrients. It had long spines on both valves, most of which are broken off in our specimen. The exterior of this bivalve is composed of resistant, long-lasting calcite; the interior of shiny, less resistant aragonite.

Spondylus gaederopus has been well known in Europe for at least 5000 years. Its thick shell and mix of calcite and aragonite made it ideal for carving beads, bracelets, rings and other cultural items. The shells were harvested in the Mediterranean and then traded throughout the continent. (Here is the outline of a 2007 European Association of Archaeologists meeting devoted just to Spondylus.) This species was one of the first bivalves named by the famous Swedish taxonomist Carl Linnaeus, and it was cited by Charles Lyell as an important species for sorting out Tertiary and Quaternary geologic time divisions.

Today the versatile shell of Spondylus gaederopus serves another purpose: helping track annual fluctuations in sea surface temperatures and salinities in the Mediterranean. These animals were long-lived and their thick shells preserve isotopes of calcium and oxygen from past seawater.

The species has lasted over 23 million years from the Early Miocene until today. I wish I could show you an image of a living Spondylus gaederopus, but the only public domain photographs available are of the related species Spondylus varians from East Timor:

In life the animal has creepy rows of eyes in its colorful mantle around the edge of the shell. For a bivalve it has a rather advanced nervous system, complete with optic lobes for the eyes.

So here’s to the multidisciplinary Spondylus gaederopus who has been in our service from Neolithic times to today. We can even say this particular specimen helped launch a paleontological career.

In praise of the humble Ro-Tap

January 25th, 2011

While we celebrate our new XRF and XRD equipment in Dr. Meagen Pollock’s petrology lab (which has already produced actual results), I thought we should also recognize our oldest piece of continuously-operated equipment in the department, the Ro-Tap Sieve Shaker:

This simple device was invented in the early 1900s by W.S. Tyler, and the company he founded still produces them today. The new versions are considerably sleeker than our massive machine. The Ro-Tap is designed to shake a series of nested sieves to sort granular materials into various size fractions. “Ro” refers to “rotate” and “Tap” to hammering at the top. You can imagine the noise that results. My Sedimentology & Stratigraphy class is using our ancient Ro-Tap (which was old when I was a student) to sort sediment samples. Each student was given a vial of an unknown sediment to describe by size distribution, mineralogy, grain shape and other characteristics. They will produce descriptive and statistical reports with conclusions about the possible environmental origins of the samples.

Joe Wilch preparing the sieve stack for the Ro-Tap.

The simple balance we use for weighing the size fractions, along with weighing trays and a datasheet.

Will Cary examining his unknown sediment sample with a photomicroscope. He is processing images through the computer on the right.

The beauty of science, especially Earth science, is that we blend the sophisticated and the simple as we describe and try to understand patterns in nature. You can stand in the basement of Scovel on some afternoons and hear the quiet purring of the X-Ray equipment as the steadfast old Ro-Tap bangs away in the background as it has for decades.

Dr. Stan Totten (’58) receives a Hall of Fame award from the Ohio Department of Natural Resources

January 25th, 2011

Ston Totten (on the left) receiving the Hall of Fame award last month (image from the ODNR website).

Wooster has always been proud of its distinguished alumnus Stan Totten (’58), a retired professor of geology at Hanover College. We are now pleased to see that the state of Ohio has recognized him for his many contributions to understanding Ohio’s geology, from checking topographic maps in his early days to producing his own glacial geology and soil maps. He even provided geological expertise for the construction of Interstates 71 and 77. This nice citation from the ODNR describes Stan’s career in more detail, and as a special touch there is an embedded video of his acceptance comments.

Well done, Stan. We should mention that Stan is also in the Hanover College Athletic Hall of Fame. And in the Wayne County Sports Hall of Fame!

Wooster’s Fossil of the Week: A most unlikely clam — rudists from the Upper Cretaceous of the Oman Mountains

January 23rd, 2011

This week’s fossil was collected on a memorable trip in 2000 to the United Arab Emirates and Oman with my friend Paul Taylor, an invertebrate paleontologist at the Natural History Museum in London. We were there to study hard substrate faunas (sclerobionts) in an Upper Cretaceous (Maastrichtian) unit known as the Qahlah (pronounced “coke-lah”) Formation. We traveled along the border between these two countries in an old Toyota Landrover plotting out the distribution and characteristics of the Qahlah and its fossils. If you want a pdf of the resulting paper (and I’m sure you do), just click here: Wilson & Taylor (2001).

One of the most interesting fossil types common in the Late Jurassic through the Cretaceous is the rudist clam. The image above is one of our Qahlah specimens known as Vaccinites vesiculosus. There are two conical rudists growing together here, with the one on the left still retaining most of its upper valve.

Rudist clams are an example of just how far evolution can go with a basic body plan. They are heterodont clams sharing a common ancestry with the typical modern Mercenaria we so love to eat (and dissect). Starting in the Jurassic, the left valve began to elongate into a cone and the right valve became a cap-like cover. They attached to each other and formed reef-like masses throughout the warm, shallow tropical seas of the Cretaceous. They were so successful that they appear to have competitively excluded most of the coral reefs. Corals had the last gurgly laugh, though, because the end-Cretaceous extinction completely wiped out the rudists, allowing the later rise of modern coral reefs.

A typical heterodont clam is in the upper left of this diagram; the rest are rudist clams. In the lower right is a drawing of the type of rudist photographed above. Diagram from Schumann & Steuber (1997; Kleine Senckenbergreihe 24: 117-122).

When I see our rudist clam specimen I’m reminded not only of its complex evolutionary heritage, but also of our own desert odyssey with grim musket-bearing Omani tribesmen, endless sand dunes stretching west, and delicious banquets of lamb and dates.

The Very First Analysis Goes To…

January 20th, 2011

WOOSTER, OH – The XRF and XRD are officially installed! We learned the basics about how to operate and maintain the XRF this afternoon. We even ran our first official sample using the EZScan. It was a difficult choice, but the honor of the first sample goes to an Icelandic basalt from Todd Spillman’s I.S. Congratulations, Todd! You’ve just made history at the College of Wooster.

I absolutely love the animation that shows the inner workings of the XRF! The cartoon shows how the x-ray tube (on the left) aims x-rays at the sample (in the middle). The resulting fluorescent x-rays (red line) travel through the slits to the crystal and finally to the detector.

Tomorrow, we’ll learn to operate the XRD. I wonder who will be the lucky owner of the first XRD sample?

New Geology X-Ray Lab

January 18th, 2011

WOOSTER, OH – Big news in the Geology Department: our new X-ray lab is being installed this week! Early last year, the Geology Department was awarded funding from the National Science Foundation to acquire X-ray instruments to enhance our robust undergraduate research program. Installation has been long awaited, highly anticipated, and wouldn’t have happened without the hard work of many people on campus. We have Ron, Patrice, Tracy, and the electricians and plumbers to thank for making it happen. The installation will probably take all week, but so far (knock on wood), things are going smoothly.

It's as if the space was designed especially for the X-ray fluorescence spectrometer (XRF).

The XRF will allow us to measure the compositions of Earth materials right here on campus. No longer will we need to send our samples (or our students) to other labs for major element analyses! Not pictured (and still wrapped in plastic) is the benchtop X-ray diffractometer (XRD), which will enable us to analyze the mineralogy of samples.

We hope our lab serves as a regional center for X-ray analyses and encourages collaborations with physicists, chemists, archeologists, and geologists. Stay tuned for updates!

Wooster’s Fossil of the Week: A cystoid (Middle Ordovician of northeastern Estonia)

January 16th, 2011

Fossils don’t get much more spherical than Echinosphaerites aurantium, an extinct creature common in the Early and Middle Ordovician of North America and Europe. These are cystoids, a somewhat informal category of filter-feeding, stalked echinoderms that are relatives of the better known crinoids. My students and I found bucketloads of them in the oil shales of the Baltic country Estonia three years ago. They are like stony golf balls.

A typical cystoid has a sac-like theca forming the bulk of the body. This theca is made of dozens to hundreds of plates of the mineral calcite fitted together like tiles. On one end of the theca is a small stem to attach it to the substrate; the other end has short brachioles, which are filter-feeding arms surrounding a tiny mouth at their base. An anus is present on the side, distinguished by a circlet of special plates.

If you look carefully at the specimen on the left in the above illustration, you’ll see at least two sclerobionts (hard-substrate dwellers) attached to the theca.  The black branching form is a graptolite (like our last Fossil of the Week) called Thallograptus sphaericola (the species name means “sphere dweller”) and the raised disk is a bryozoan.

Every once in awhile the cystoids in Estonia were buried quickly and did not fill with sediment. The hollow space within became a kind of geode with crystals of calcite growing from the thecal plates inward. Each plate is a single crystal of calcite, so the crystals grew syntaxially (maintaining crystallographic continuity). These specimens are spectacular if broken open carefully so they don’t shatter into a thousand sparkles.

Wooster’s Fossil of the Week: A three-branched graptolite (Lower Ordovician of southeastern Australia)

January 9th, 2011

This week I’m correcting a mistake I’ve been making in my paleontology courses for nearly thirty years. Our subject is a graptolite from the teaching collections — a specimen that has been at least cursorily examined by all of my paleontology students. It is not a particularly pretty fossil, but an important one for biostratigraphy and evolution.

Graptolites were colonial marine organisms which thrived from the Late Cambrian (roughly 510 million years ago) into the Early Carboniferous (about 350 million years ago). Their colonies, termed rhabdosomes, were not mineralized, so they are most commonly preserved as thin carbon films like our featured specimen. The rhabdosome usually began with a single individual, known as a sicula, that budded branches called stipes. Each stipe is lined with cup-like thecae that held what we presume were filter-feeding individuals termed zooids (much like bryozoans). The number of stipes per rhabdosome varies considerably, from one to dozens. Some graptolites were sessile benthic epifaunal (attached to the seafloor on hard surfaces) while others were planktic (suspended or floating).

Our specimen above is the planktic graptolite Pendeograptus fruticosus from the Lower Ordovician (about 477-474 million years old) near Bendigo, Australia. There are actually two specimens overlapping here. I’ve labeled one sicula as “S1” and the other as “S2”.

This is where my mistake began. I identified these graptolites during my first professorial year as Tetragraptus fruticosus, believing that there were two specimens with, as you might guess from the name, four stipes each. When I counted the actual stipes present, though, I found only three each. I believed, though, that graptolites had either one, two, four or many stipes, so specimens with only three had to have one stipe missing or folded over as to be invisible. So for the curious student who counted three where there should have been four, I confidently explained the preservational oddity. That both specimens lacked the fourth stipe did not apparently shake my resolve.

It was only after photographing this specimen that I looked closely enough to see that, indeed, three stipes are present and there is no evidence of a fourth for either rhabdosome. (I added numbers and letters to the above image to delineate the stipes.) Maybe there really are three-stiped graptolites? This was easily enough confirmed by simply Googling “three-stiped graptolite”. Who knew? This version of “Tetragraptus” is actually the genus Pendeograptus. Oops.

Turns out that our Pendeograptus fruticosus is part of an evolutionary series proceeding from four to three to two stipes. The three-stiped version we have is an indicator for the Australian Bendigonian Stage and a global index fossil for this narrow time interval 477 to 474 million years ago.

You can now see this specimen (without the red labels) on the Wikipedia page for graptolites. I’m correcting my mistake and sharing a useful little fossil with the world.

Wooster’s Fossil of the Week: The tabulate coral Aulopora (Devonian of northwestern Ohio)

January 2nd, 2011

We’re going to start 2011 with a new blog feature: Fossil of the Week! My colleagues, of course, are welcome to also start “Mineral of the Week”, “Structural Geologic Feature of the Week”, or “Climate Event of the Week”.  The more the better to keep our blog active through the winter!

This week’s fossil was collected by Brian Bade of Sullivan, Ohio, and donated to Wooster as part of my hederelloid project.  It is a beautiful specimen of the tabulate coral Aulopora encrusting a brachiopod valve from the Silica Shale (Middle Devonian — about 390 million years old) of northwestern Ohio.  Auloporid corals are characterized by an encrusting habit, a bifurcating growth pattern, and horn-shaped corallites (individual skeletal containers for the polyps).

What is especially nice about this specimen is that we are looking at a well preserved colony origin.  The corallite marked with the yellow “P” is the protocorallite — the first corallite from which all the others are derived.  You can see that two corallites bud out from the protocorallite 180° from each other.  These two corallites in turn each bud two corallites, but at about 160°.  This pattern continues as the colony develops (a process called astogeny).  The angles of budding begin to vary depending on local obstacles; they never again go below 160°.

The polyps inside the corallites are presumed to have been like other colonial coral polyps.  Each would have had tentacles surrounding a central opening, and all were connecting by soft tissue within the skeleton.  They likely fed on zooplankton in the surrounding seawater.  This type of coral went extinct in the Permian, roughly 260 million years ago.

Again, we thank our amateur geologist friends for such useful donations to the research and educational collections in the Geology Department at Wooster.