Wooster’s Fossils of the Week: A pair of molded nautiloids from the Upper Ordovician of northern Kentucky

October 24th, 2014

1 Nautiloid pair 091314Two nautiloids are preserved in the above image of a slab from the Upper Ordovician of northern Kentucky. (I wish I knew which specific locality. This is why paleontologists are such fanatics about labeling specimens.) The top internal mold (meaning it is sediment that infilled a shell now dissolved away) has been covered in a previous blog entry. This week I want to concentrate on the nautiloid at the bottom.

These nautiloids belong to the Family Orthoceratidae McCoy, 1844, which existed from the Early Ordovician (490 million years ago) through the Triassic (230 million years ago). They had conical, aragonitic shells with walls inside separating chambers (camerae) and a central tube (the siphuncle) connecting them. They were swimming (nektic) predators that could control their buoyancy through a mix of gases and liquids in the camerae mediated by the siphuncle.

What is most interesting here is the preservation of these nautiloids. The aragonitic shells were dissolved away at about the same time the internal sediment was cemented, forming the internal molds. These molds were exposed on the seafloor, attracting encrusting organisms. This means the dissolution and cementation took place quickly and in the marine environment, not after burial. This rapid dissolving of aragonite and cementation by calcite is typical of Calcite Sea geochemistry, something we don’t see in today’s Aragonite Seas.
2 Nautiloid siphuncle 091314Above is a close view of the cemented siphuncle of the lower nautiloid, heavily encrusted by a trepostome bryozoan.
3 Bryozoan undersideEven more cool, the outside of the lower nautiloid was encrusted by several trepostome bryozoan colonies. When the shell dissolved it left the undersides of these bryozoans exposed, as seen above. These undersides often contain the remains of shelly organisms the bryozoans encrusted (see the Independent Study project by Kit Price ’13) and even soft-bodied animals (epibiont bioimmuration; see Wilson et al., 1994).

A neat package here resulting from biological, sedimentological and geochemical factors.

References:

Palmer, T.J., Hudson, J.D. and Wilson, M.A. 1988. Palaeoecological evidence for early aragonite dissolution in ancient calcite seas. Nature 335 (6193): 809–810.

Sweet, W.C. 1964. Nautiloidea — Orthocerida, in Treatise on Invertebrate Paleontology. Part K. Mollusca 3, Geological Society of America, and University of Kansas Press, New York, New York and Lawrence, Kansas.

Wilson, M.A., Palmer, T.J. and Taylor, P.D. 1994. Earliest preservation of soft-bodied fossils by epibiont bioimmuration: Upper Ordovician of Kentucky. Lethaia 27: 269-270.

Wooster’s Fossils of the Week: Bivalve borings, bioclaustrations and symbiosis in corals from the Upper Cretaceous (Cenomanian) of southern Israel

October 17th, 2014

Fig. 2 Aspidiscus1bw_scale 585The stark black-and-white of these images are a clue that the fossil this week has been described in a paper. Above is the scleractinian coral Aspidiscus cristatus (Lamarck, 1801) from the En Yorqe’am Formation (Cenomanian, Upper Cretaceous) of southern Israel. The holes are developed by and around tiny bivalves and given the trace fossil name Gastrochaenolites ampullatus Kelly and Bromley, 1984. This specimen was collected during my April trip to Israel, a day recorded in this blog. I crowd-sourced the identification of these corals, and they were highlighted as earlier Fossils of the Week. Now I’d like to describe them again with new information, and celebrate the publication of a paper about them.

En Yorqe'am040914aThis is the exposure of the En Yorqe’am Formation where Yoav Avni and I collected the coral specimens approximately 20 meters from its base in Nahal Neqarot, southern Israel (30.65788°, E 35.08764°). It is an amazingly fossiliferous unit here with brachiopods, stromatoporoid sponges, zillions of oysters, gastropods, ammonites and the corals.

The abstract of the Wilson et al. (2014) paper tells the story: “Specimens of the small compound coral Aspidiscus cristatus (Lamarck, 1801) containing evidence of symbiosis with bivalves have been found in the En Yorqe’am Formation (Upper Cretaceous, early Cenomanian) of southern Israel. The corals have paired holes on their upper surfaces leading to a common chamber below, forming the trace fossil Gastrochaenolites ampullatus Kelly and Bromley, 1984. Apparently gastrochaenid bivalve larvae settled on living coral surfaces and began to bore into the underlying aragonitic skeletons. The corals added new skeleton around the paired siphonal tubes of the invading bivalves, eventually producing crypts that were borings at their bases and bioclaustrations at their openings. When a boring bivalve died its crypt was closed by the growing coral, entombing the bivalve shell in place. This is early evidence of a symbiotic relationship between scleractinian corals and boring bivalves (parasitism in this case), and the earliest record of bivalve infestation of a member of the Suborder Microsolenina. It is also the earliest occurrence of G. ampullatus.”

Fig. 3 BoringPair2bw_scale 585 Paired apertures of Gastrochaenolites ampullatus in the coral Aspidiscus cristatus.

Fig. 4 EmbeddedBivalve1bw_scale_rev 585Polished cross-section through a specimen of Gastrochaenolites ampullatus in an Aspidiscus cristatus coral. In the lower left of the chamber are layered carbonates (A) representing boring linings produced by the bivalve. An articulated bivalve shell (B) is preserved in the chamber. The chamber has been roofed over by coral growth (C).

Thank you very much to Tim Palmer and Olev Vinn for their critical roles in this paper, and, of course, thanks to Yoav Avni, the best field geologist I know.

References:

Avnimelech, M. 1947. A new species of Aspidiscus from the Middle Cretaceous of Sinai and remarks on this genus in general. Eclogae geologicae Helvetiae 40: 294-298.

Gill, G.A. and Lafuste, J.G. 1987. Structure, repartition et signification paleogeographique d’Aspidiscus, hexacoralliaire cenomanien de la Tethys. Bulletin de la Societe Geologique de France 3: 921-934.

Kleemann, K., 1994. Associations of corals and boring bivalves since the Late Cretaceous. Facies 31, 131-140.

Morton, B. 1990. Corals and their bivalve borers: the evolution of a symbiosis. In: Morton, B. (Ed.), The Bivalvia: Proceedings of a Memorial Symposium in Honour of Sir Charles Maurice Yonge (1899-1986) at the 9th International Malacological Congress, 1986, Edinburgh, Scotland, UK. Hong Kong University Press, Hong Kong, pp. 11-46

Pandey, D.K., Fürsich, F.T., Gameil, M. and Ayoub-Hannaa, W.S. 2011. Aspidiscus cristatus (Lamarck) from the Cenomanian sediments of Wadi Quseib, east Sinai, Egypt. Journal of the Paleontological Society of India 56: 29-37.

Wilson, M.A., Vinn, O. and Palmer, T.J. 2014. Bivalve borings, bioclaustrations and symbiosis in corals from the Upper Cretaceous (Cenomanian) of southern Israel. Palaeogeography, Palaeoclimatology, Palaeoecology 414: 243-245.

 

The geological setting of Fort Necessity, Pennsylvania

October 11th, 2014

Great Meadows 101114On July 3, 1754, colonial lieutenant Colonel George Washington fought and lost a small battle on this site in southwestern Pennsylvania. He and his 400 men had built this makeshift fort about a month before in anticipation of an attack by several hundred French soldiers and their Indian allies. The French were incensed at Washington and his troops after they killed or captured most of a French party at the Battle of Jumonville Glen two months before. (Accounts vary as to who was at fault for that deadly encounter as France and Britain were not at war.) The Battle of Fort Necessity was just one day long, and the British under Washington had the worst of it. Washington accepted French surrender terms and he and his men were allowed to march home. This pair of skirmishes between the French and British started the French and Indian War,  known outside of the USA as the Seven Years’ War. It quickly became a global fight between empires; in many ways it was the first modern world war. And it all started in this lonely part of the Pennsylvania country.

Washington chose to place his ill-fated fort, a reconstruction of which is shown above, in a high grassy spot known as the Great Meadows. It is situated near two passes in the Allegheny Mountains, and thus sits strategically beside major trails. Washington liked the area because there was plenty of feed for his pack animals and horses, lots of available water (too much, it turned out), and it was not in the midst of the endless woods of the region.
Screen Shot 2014-10-12 at 5.19.55 PMThis geological map of the area (from the National Park Service) shows that the fort was situated on the Upper Carboniferous Glenshaw Formation. This unit has much clay, trapping water in the thin soil above (“Philo Loam“). Further, the area is a floodplain, thus making the area a kind of wetland with grasses and sedges. Great for horse grazing, not so good for walls, buildings or trenches.
Entrenchments 101114Here we see the shallow entrenchments made by Washington and his men as they awaited attack. The clayey soil and pouring rain made a mess of these boggy trenches.

Fort inside 101114Inside the fort was a simple square building used mainly to keep supplies and wounded men dry, During the battle it was partially flooded with rainwater.

British view 101114This is the British view from the fort of the surrounding woods. Washington miscalculated his placing of the fort because the French and Indians could easily hit it with musket shots while hiding among the trees.

French Indian view 101114The French and Indian view of the hapless fort. It was easy to rain bullets on the British from the woods with little fear of the return fire.

Braddock road trace 101114Nearby is a trace of the military road Washington’s unit had blazed through the Pennsylvania woods on their way to the French Fort Duquesne in what is now Pittsburgh. The British General Edward Braddock enlarged this road the next year in his famous march to a spectacular defeat nearby (the “Battle of Monongahela“).

We can’t fault Washington too much for his choice of a fort location. He did not have the resources to clear a large patch of forest, so the meadow would have to do. He expected to be reinforced soon, so he saw the fort as a temporary measure of protection. The rain was beyond his control that July day, and the clay-rich meadow floor ensured wet misery and ruined supplies. The French surprisingly gave good terms for surrender because they were wet, too, in those woods, and they also expected more British and colonial troops would arrive soon. They feared being surrounded, and so thought their message to Washington and his countrymen had been sufficiently made. How different our world would be if the French were not so generous here in southwestern Pennsylvania!

Additional Reference:

Thornberry-Ehrlich, T. 2009. Fort Necessity National Battlefield Geologic Resources Inventory Report. Natural Resource Report NPS/NRPC/GRD/NRR—2009/082. National Park Service, Denver, Colorado.

Wooster’s Fossil of the Week: An early bryozoan on a Middle Ordovician hardground from Utah

October 10th, 2014

ORBIPORA UTAHENSIS (Hinds, 1970) 072014Last week I presented eocrinoid holdfasts on carbonate hardgrounds from the Kanosh Formation (Middle Ordovician) in west-central Utah. This week we have a thick and strangely featureless bryozoan from the same hardgrounds. It is very common on these surfaces, forming gray, perforate masses that look stuck on like silly putty. Above you see one on the left end of this hardground fragment. (The circular object to the right is another eocrinoid holdfast.)
Kanosh bryo eo 072014Here is a closer view of the bryozoan, again with one of those ubiquitous eocrinoids encrusting it. The holes are the zooecial apertures. Each zooecium is the skeletal component of a living bryozoan individual (zooid). Note that the walls are thick and granular between the zooecia. All the zooecia look pretty much the same, and there are no other structures like spines, pillars or maculae. This is about as simple as a bryozoan gets.

It is impossible to be certain without a thin-section or acetate peel showing the interior, but I’m pretty sure this Kanosh bryozoan is Orbipora utahensis (Hinds, 1970). It matches fairly well the description in Hinds (1970), who named it Dianulites utahensis, and it fits within the redescription by Ernst et al. (2007).

Several years ago we would have called this a trepostome bryozoan and left it at that. These are, after all, the “stony bryozoans” with thick calcite skeletons and long zooecia. However, the group to which Orbipora belongs is unusual because they have no polymorphs (small zooecia different from the primary zooecia) and have granular skeletal textures rather than laminated. We think the granular walls may be because the original skeletons were made of high-magnesium calcite that later altered to low-magnesium calcite and dolomite, losing details of the microstructure. Orbipora is thus in an as yet undescribed new order of bryozoans. [Update: See comment below from Paul Taylor.]

The Kanosh hardgrounds and their attaching faunas are important in geological and biological history because they are telling us something about the geochemical conditions of the seawater when they formed. We think this was a peak time of Calcite Seas, when low-magnesium calcite was a primary marine precipitate and carbon dioxide levels were high in the atmosphere and seawater. Hardgrounds would have formed rapidly because of early cementation, and aragonite and high-magnesium skeletons would have altered soon after death. The abundant Kanosh communities and substrates are critical evidence for these conditions that were superimposed on the Great Ordovician Biodiversification Event (GOBE). We thus have a delightful combination of seawater geochemistry (and, ultimately, the tectonics that controls it) and evolution intertwined in the history of these rocks and fossils.

References:

Ernst, A., Taylor, P.D. and Wilson, M.A. 2007. Ordovician bryozoans from the Kanosh Formation (Whiterockian) of Utah, USA. Journal of Paleontology 81: 998-1008.

Hinds, R.W. 1970. Ordovician Bryozoa from the Pogonip Group of Millard County, western Utah. Brigham Young University Research Studies, Geology Series 17: 19–40.

Marenco, P.J., Marenco, K.N., Lubitz, R.L. and Niu, D. 2013. Contrasting long-term global and short-term local redox proxies during the Great Ordovician Biodiversification Event: A case study from Fossil Mountain, Utah, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 377: 45-51.

Wilson, M.A., Palmer, T.J., Guensburg, T.E., Finton, C.D. and Kaufman, L.E. 1992. The development of an Early Ordovician hardground community in response to rapid sea-floor calcite precipitation. Lethaia 25: 19-34.

Wooster’s Fossils of the Week: Eocrinoid holdfasts on a Middle Ordovician hardground from Utah

October 3rd, 2014

Kanosh Hardground 072014 smBack in the late 1980s and early 1990s, several students and I did fieldwork in the Middle Ordovician Kanosh Formation in west-central Utah. One year we were joined by my friend Tim Palmer of the University of Aberystwyth. Together, Chris Finton (’91), Lewis Kaufman (’91), Tim and I put together a paper describing the carbonate hardground communities in this remarkable formation (Wilson et al., 1992). At top is an image of one of the surface of one of these hardgrounds. It is covered with holdfasts of rhipidocystid eocrinoids, a kind of primitive echinoderm.
Fossil Mountain UtahMost of the hardgrounds we studied in the Kanosh Formation were found here at Fossil Mountain near Ibex, Utah. (If you want to consider Ibex a place, at least.) It was a beautiful place to work, and it is still highly productive for geologists and paleontologists (see Marenco et al., 2013, for the latest investigation).

Kanosh eocrinoid 2The encrusters on the Kanosh hardgrounds are dominated by two groups: bryozoans (which we’ll highlight next week) and stemmed echinoderms (this week’s subject). The echinoderms are represented by thousands of these small attachment structures called holdfasts. The stem of the echinoderm was attached here to the hardground. The entire skeleton of the echinoderm, including the hardground, is made of low-magnesium calcite, so they are very well preserved. Surprisingly, the hardground communities in the Kanosh have very few sponges or borings.

Kanosh eocrinoid 3 072014The holdfasts come in a few varieties with subtle morphological differences. Here we have one with a tri-radiate center.

Kanosh eocrinoids 1Sometimes the holdfasts blended together on the hardground surface, which was probably the result of competition for attachment space. Note the tri-radiate centers.

Mandalacystis diagramFrom a few plates we found, it appears that the rhipidocystid eocrinoid holdfasts are from a creature like Mandalacystis, which is pictured above from Figure 1 of Lewis et al. (1987). We can’t tell for certain without more of the skeleton, but the holdfasts are very similar to what has been described for the genus.

These Middle Ordovician hardgrounds were formed at an interesting time in the chemistry of the oceans and the development of marine invertebrate faunas. More on that next week!

References:

Ernst, A., Taylor, P.D. and Wilson, M.A. 2007. Ordovician bryozoans from the Kanosh Formation (Whiterockian) of Utah, USA. Journal of Paleontology 81: 998-1008.

Lewis, R.D., Sprinkle, J., Bailey, J.B., Moffit, J. and Parsley, R.L. 1987. Mandalacystis, a new rhipidocystid eocrinoid from the Whiterockian Stage (Ordovician) in Oklahoma and Nevada. Journal of Paleontology 61: 1222-1235.

Marenco, P.J., Marenco, K.N., Lubitz, R.L. and Niu, D. 2013. Contrasting long-term global and short-term local redox proxies during the Great Ordovician Biodiversification Event: A case study from Fossil Mountain, Utah, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 377: 45-51.

Wilson, M.A., Palmer, T.J., Guensburg, T.E., Finton, C.D. and Kaufman, L.E. 1992. The development of an Early Ordovician hardground community in response to rapid sea-floor calcite precipitation. Lethaia 25: 19-34.

In the footsteps of Charles Darwin: Geological excursion into the Central Andes

October 1st, 2014

01ViewOppositeAconcagua100114MENDOZA, ARGENTINA–Today I had one of the finest geological field trips in my life. The scenery was stunning, the geology extraordinary, and the history deeply moving. Being able to share the experience with so many of my geologist friends, old and new, was a bonus. I also thought how much my Wooster Geology colleagues would have enjoyed this excursion. There were volcanics for Meagen, glacial deposits for Greg, and the most extraordinary structural geology for Shelley. This was a mid-meeting field trip of the Fourth International Palaeontological Congress entitled “Darwin and the Highest Andes”. It was led by Victor Ramos and Laura Giambiagi.

The purpose of the trip was to explore the Central Andes from Mendoza almost to the border with Chile, cutting a cross-section through the ranges. We followed the route Charles Darwin took between March 29 and April 5, 1835. This experience was heaven for me: history and geology combined.02TectonicContext100114The above image is from Jordan et al. (1983, issue 3 of Episodes) reproduced in our guidebook. It shows the flat-slab subduction beneath the Andes as well as the three ranges we visited (Precordillera, Frontal Cordillera, and Principal Cordillera). We traveled from right to left on this diagram perpendicular to the mountains.

03Precordillera101014The Precordillera was impressive enough by itself. Here is the dirt road we followed up the eastern slope. It is an enlarged mule path used for centuries as part of the road between Chile and Argentina. Most famously this is the route General José de San Martín used in his epic 1817 Crossing of the Andes to defeat the Spanish as part of the Wars of Independence. Charles Darwin, of course, took the same route in 1835.

04Guanico100114We saw many guanacos (Lama guanicoe) on the way up into the mountains. These camelids native to the area have delightful black faces and skittish ways.

05PrecordilleraNearTop100114Looking west across the Precordillera near the top. The clouds we see stayed around the Mendoza area, but we were above them and had a wonderful sunny day.

06DarwinTree100114Our first major stop was at a petrified forest in Triassic rift valley sediments. Darwin described these tree trunks, which are coarsely replaced by calcite, as part of a buried conifer forest that had been tilted to the west. The sediments are mostly fine volcanic grains. He counted 52 trees, but I found only a few during our stop.

07GuidebookPillar100114Darwin wrote that one of the fossil trees reminded him of “Lot’s wife turned into a pillar of salt.” Who could guess that one of my photographs from Israel would make it into the guidebook as a consequence!

08DarwinForestViewWest100114The view west from Darwin’s Forest shows the beginning of the Frontal Cordillera. The terrain here is very much like that of the Mojave Desert in California, even including a species of Larrea (creosote bush).

MZ and me from Michal Rakocinski1My Polish colleague Michał Zatoń and me with the magnificent Frontal Cordillera. Thank you Michal Rakocinski for the image.

09MarkDarwinForest100114Here I am at a plaque honoring Darwin at the fossil forest. An earlier marker had been destroyed by a small group of local Creationists. Evolution is not very controversial in Argentina, but some of their Creationists are apparently vandals. This plaque has been made especially thick and heavy.

10LunchStop100114We ate lunch while admiring this view of Triassic volcanics near the start of the Frontal Cordillera. The stone work is the Picheuta Bridge.

11PuentedelInca100114We are now in the Principal Cordillera of the Andes. I’m looking along old railroad tracks at Puente del Inca into the magnificent High Andes.

12SouthviewPuentedelInca100114This is the opposite view. Note the fine, fine weather. We needed only light jackets or sweaters.

13BridgePuentedelInca100114Puente del Inca itself is a natural bridge of travertine-cemented landslide debris. Thermal springs like these are scattered along the axes of the Principal Cordillera of the Andes. This bridge, sadly, had nothing to do with the Incas, although they did extend this far south.

14GuidebookCrossSection100114Darwin drew a cross-section of the Principal Cordillera, including this site at Puente del Inca (on the middle right). This is an image from the guidebook of our trip.

15Aconcagua100114The most impressive part of our trip (I’m avoiding “high point”!) was this view we had of Aconcagua, the highest mountain in the southern and western hemispheres. Essentially it is Miocene volcanic rocks unconformably atop folded Cretaceous sedimentary deposits thrust on top of Paleogene rocks. This iconic mountain often has snow blowing off its crest, producing white clouds. Darwin mistook these for ash emissions and thought this was an active volcano.

16DarwinShelter100114Our last stop was at Casuchas del Virrey, a brick structure built in 1765 for Spanish officials making the hazardous trip between what would become Chile and Argentina. (They would have rather communicated by sea through the Magellan Strait, but the British were making that difficult.) Darwin himself stayed here, so this little building is often called “Darwin’s Shelter”. The doorway is so high because of the accumulation of snow here in the winter.

17VictorRamos100114Thank you to Victor Ramos for being such an effective, knowledgeable, humorous and patient guide for this trip. He is a structural geologist, but also quite good with sedimentology, paleontology and history. He made this excursion one we will long treasure in our memories of the Andes. Thank you also to my Wooster colleagues for making this trip possible for me.

Darwin and the High Andes copy(Late update, October 4th: Field trip group photo courtesy of Beatriz Aguirre-Urreta.)

Nothing quite like the feeling of completing your presentation: Day 2 of the International Palaeontological Congress

September 30th, 2014

DSC_4540MENDOZA, ARGENTINA–I promise, the images will be much more interesting in the next post! Today we concentrated on talks. I finally was able to deliver mine in the same session as Leif Tapanila above. It was a crowded little room, but the presentations kept us well entertained and informed.

I learned a lesson: without any outward indication of the time in a talk, I do tend to prattle on. There were no clocks or green-yellow-red lights for the speakers, and I was reluctant to try to read my watch in the darkness. To my surprise one of the session chairs told me mid-talk that I had two minutes left. Aghast and in a panic as the rule-follower I am, I sprinted to my last slides and finished. The organizers were laughing afterwards, though, because when they say “two minutes” it is for Latin American speakers who will typically take at least five minutes to end. I had a full five minutes, but as time-structured Norte Americano, I used only one!

My talk was titled “Changing Diversity and Intensity of Marine Macroboring Through the Phanerozoic”. Two critical slides, for the record, are below. They were surrounded by caveats!

Slide48_093014Slide49_093014I even earned a certificate! (As did everyone else.)

DSC_4551I very much enjoyed the presentations by Luis Buatois and Gabriela Mangano on Ediacaran and Early Cambrian bioturbation and trace fossils, as well as a talk by Al Curran and colleagues on the trace fossil Ophiomorpha. Leif Tapanila’s lecture on Triassic wood borings was fascinating, as was a spectacular presentation on Early Jurassic dinosaur nests and eggs in Patagonia.

IPC4 talk from Michal RakocinskiMichal Rakocinski managed to get a photo of me as I started my talk. I’ve never seen myself before in talking mode.

Tomorrow is field trip day, so this blog will return to images of geological scenery!

The Fourth International Palaeontological Congress starts well

September 29th, 2014

Zaton092914MENDOZA, ARGENTINA–After an excellent opening lecture last night by Dr. Beatriz Aguirre-Urreta (“Palaeontology in the Southern Hemisphere: Benchmarks in the History of Discovery and Research”), we got down to the technical talks today in the Mendoza Sheraton for the 4th International Paleontological Congress. There were many presentations to choose from, as usual, so I had an eclectic mix today. Above is my colleague Michał Zatoń delivering an interesting talk on Devonian faunas in Laurussia. I also enjoyed a presentation by Linda Frey on Devonian paleoecology in Morocco (full disclosure: Paul Taylor and I were in the long list of co-authors), Andrei Dronov on Ordovician trace fossils in Siberia, and Bruce Runnegar on the classic Ediacaran fossil Dickinsonia. It is a joy to have so many of my people in the same place at the same time.

Posters092914Well, usually. As you can quickly deduce from this scene, the almost 1000 attendees at this meeting have stretched the capacity of the venue. This is one of the lanes for the poster session. I got in about six feet. Nevertheless, I had a good time speaking with Marcelo Carrera about his Lower Ordovician tabulate corals, and Alycia Stigall (whose poster is visible on the right) on her fantastic online Ordovician Atlas program.

Tomorrow I have a Paleontological Society meeting in the morning, and then I give my talk in the afternoon. As always, I’ve divided this meeting mentally into two parts: pre-talk and post-talk!

Wooster Geologist over the Andes

September 27th, 2014

Andes092714

MENDOZA, ARGENTINA–I have just arrived in Argentina for the Fourth International Palaeontological Congress to be held in this city all next week. I thank me colleagues at Wooster for making this possible, especially Shelley Judge who is teaching my History of Life class in my absence. I also thank the Faculty Development Fund at Wooster.

It was a treat to have a window seat in the last leg of our air journey from Santiago, Chile, to Mendoza over the Andes. Sure, it was cloudy over the crest of the mountains, but the views were still fantastic on either side. Above is a view of the Argentinian foothills just at the edge of cloud cover.

DSC_4521Soon after take-off from Santiago I was impressed with the lush greenery of the Chilean foothills leading to the Andes themselves. This is the rainy side of the mountains.

DSC_4527The contrast is dramatic between the western and eastern sides. This is a classic rain shadow effect.

DSC_4531Here is an Argentine oilfield near Mendoza. Each of the cleared spots has a pump jack, and the tank farm is visible near the middle.

DSC_4532This is the scene from my hotel window of Mendoza. Not exactly enchanting, I must say, but the views on the other side of the hotel show the tall, snow-capped mountains.

All is well with me (as in no kidney stones). It is a joy to see so many very good friends as we gather together for what will be a spectacular meeting of hundreds of international paleontologists.

Wooster’s Fossil of the Week: A crinoid calyx from the Upper Ordovician of southern Ohio

September 26th, 2014

Xenocrinus baeri (Meek, 1872)_585This week’s contribution from the Wooster collections will be short. If all is going well, as this is posted I’m on my way to the Fourth International Palaeontological Congress in Mendoza, Argentina. I hope to have a few posts from that exotic place!

The fossil above is the crown of a monobathrid crinoid called Xenocrinus baeri (Meek, 1872). It was found by Bianca Hand (Wooster ’14) in the Bull Fork Formation (Upper Ordovician, Richmondian) on an Invertebrate Paleontology field trip to the emergency spillway at Caesar Creek State Park in southern Ohio (seen below). Thank you to my friend Bill Ausich of The Ohio State University for identifying this fossil. It is an unprepared specimen of a common species, and it is not nearly so flashy as in other collections. Still, it is one of the best finds from our class field trips, and it is cool. The calyx is on the right and mostly buried in matrix. Four filter-feeding arms extend to the left. Where the matrix is broken away on the far right you can see tiny ossicles from the pinnules on the arms. Someone using a needle very carefully under a microscope could expose more details of this crinoid, but I like leaving something to the imagination!
CaesarCreek2011References:

Schumacher, G.A. and Ausich, W.I. 198). New Upper Ordovician echinoderm site: Bull Fork Formation, Caesar Creek Reservoir (Warren County, Ohio). The Ohio Journal of Science 83: 60-64.

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