Archive for May, 2015

Wooster’s Fossil of the Week: Petrified conifer wood

May 29th, 2015

1Petrified Wood 052615 585This is one of the most beautiful fossils in Wooster’s teaching collections. It is a polished section of petrified wood. It has vibrant colors and exquisite detail, as you’re about to see. Unfortunately any label that accompanied this specimen disappeared long ago. No matter how fantastic a fossil is, without its original location and stratigraphic context it has little scientific value. It works for our teaching collection, but I can’t tell you the age of the specimen, nor where it was found.
2Petrified wood close 052615 585Petrified wood is one of the most common types of fossil known to the public because of its abundance, attractiveness, hardiness (many a house out west has been built with petrified logs), and variety. Through the process of permineralization, minerals (quartz and chalcedony in this case) have infiltrated the porous organic structure, giving us three-dimensional, highly detailed preservation. This wood was first buried in low-oxygen sediments before it could decay on the forest floor. Groundwater circulated through the conductive tissue of the wood, depositing minerals in and around the cell walls of lignin and cellulose.

3Season of wood 052615 585It is hard to believe as we look closer and closer at the specimen that this is a fossil and not modern wood. Here we see the structure of the annual rings. The light-colored section is the new growth, the darker is when growth slowed at the end of the season. Our Wooster dendrochronologists, Greg Wiles and Nick Wiesenberg, could tell from this view that our tree was some kind of conifer.

4Polished petrified wood cells 585An even closer view of the same specimen. Now the perspective is dominated by vertical elements (rays) extending from the core of the tree outwards.

5Wood cells closest 052615 585This is as close as I could get with our photographic equipment. The cell walls and intervening rays are very distinct. Again, we’re looking at minerals here, not the original wood!

Again, fully label your fossils when you collect them. Because it has no locality information, this unlabeled specimen has little scientific worth. Too bad!


Hickey, L.J. 2010. The Forest Primeval: The Geologic History of Wood and Petrified Forests. Yale Peabody Museum Series, 62 pp.

Wooster’s Fossils of the Week: A Silurian encrinite from southwestern Ohio

May 22nd, 2015

BrassfieldEncrinite585_041915The above rock was collected on our Sedimentology & Stratigraphy class field trip last month. It is an average piece of weathered Brassfield Formation (Early Silurian, Llandovery) from Oakes Quarry Park near Fairborn, Ohio (N 39.81472°, W 83.99471°). It is made almost entirely of crinoid fragments, and has a pleasant pinkish hue, most of which comes from the crinoid bits themselves. If you look closely you can see crinoid thecal plate fragments as well columnals and pluricolumnals.

This kind of limestone in which echinoderm ossicles make up the bulk of the grains is known as an encrinite. I first learned about encrinites from my colleague Bill Ausich of The Ohio State University, who has written the best assessments of encrinites on a regional scale. Encrinites are well-washed biosparite grainstones typically deposited between fair weather and storm wave bases on shallow shelves in low latitudes. They are surprisingly common from the Ordovician into the Jurassic, but then the disappear from the rock record as crinoids declined in abundance in shallow environments.

We’ve seen encrinites before in this blog from the Silurian of Estonia, the Triassic of Poland, and the Jurassic of Utah.


Ausich, W.I. 1986. Early Silurian inadunate crinoids (Brassfield Formation, Ohio). Journal of Paleontology 60: 719-735.

Ausich, W.I. 1997. Regional encrinites: a vanished lithofacies. In: Paleontological events: stratigraphic, ecologic and evolutionary implications, p. 509-519. Columbia University Press, New York.

Ausich, W.I. and Deline, B. 2012. Macroevolutionary transition in crinoids following the Late Ordovician extinction event (Ordovician to Early Silurian). Palaeogeography, Palaeoclimatology, Palaeoecology 361: 38-48.

Hunter, A.W. and Zonneveld, J.P. 2008. Palaeoecology of Jurassic encrinites: reconstructing crinoid communities from the Western Interior Seaway of North America. Palaeogeography, Palaeoclimatology, Palaeoecology 263: 58-70.

Tang, C.M., Bottjer, D.J. and Simms, M.J. 2000. Stalked crinoids from a Jurassic tidal deposit in western North America. Lethaia 33: 46-54.

Wooster Geologists (and a Wooster Chemist) visit Brown’s Lake Bog

May 21st, 2015

1 Greg with fernsI was privileged today to visit Brown’s Lake Bog, a Nature Conservancy preserve, with Greg Wiles, Nick Wiesenberg, and Kim Carter (Chemistry ’16). Greg and Nick have been here many times with students and colleagues, including some epic sessions of ice drilling. It is an important site for both the rare plants that live here and the geological context of a relict kame-and-kettle topography from the last glaciation. Greg has set up over the years a series of shallow well measuring stations and has cored several of the old-growth oaks for tree-ring analyses. Kim, a student of Paul Edmiston, was looking for sites to place Osorb samples to adsorb various chemicals in run-off waters. I was along just for fun.

2 Brown's Lake Bog signThe Nature Conservancy maintains the 80-acre site, including trails and a boardwalk through the woods to the bog itself.

3 Kame at Brown's Lake BogNear the head of the bog trail is a nice view of a plowed kame. This is a geomorphological feature formed when sediment accumulated in a depression on a glacial ice sheet and then was deposited as the ice melted. The bog itself is a kettle, the result of a melting block of ice buried in the sediment produced at the margin of a retreating glacier.

4 Greg and transducerGreg retrieving a transducer, which measures water level changes, from one of his wells.

5 Nick and downloaded dataNick takes the transducer, cleans it up, and then downloads the data into a laptop computer. It shows hourly records of temperature and water level changes in the well. (I know, that’s George W. Bush peaking around the results window. Ask Nick why!)

6 Nick and rain collectorNick is here recovering a rainwater sample from a collector. This water is isotopically examined by researchers at the University of Cincinnati as part of a long-term project.

7 Brown's Lake Bog 585Here is the beautiful bog itself, slowly being filled by sediment and encroaching shrubbery. The water is surrounded by a thick floating mat of Sphagnum moss.

8 Sarracenia purpurea & SphagnumThe Sphagnum mat supports a fascinating array of rare plants. It is an acidic, nutrient-poor environment, so the plants are quite specialized.

9 Sarracenia purpurea pitchers 585The stars of the boggy botanical delights are the Northern Pitcher Plants (Sarracenia purpurea). These trap insects inside their fluid-filled cavities surrounded by slippery walls. That is how they obtain most of their nutrients.

10 Sarracenia purpurea flowerThese tall, downward-facing blooms are the flowers of the pitcher plants. I imagine they are high above the pitchers so the pollinating insects don’t get eaten!

11 Drosera_rotundifolia 585Finally, here’s a nice Round-Leaved Sundew (Drosera rotundifolia), another cool carnivorous plant common on the Sphagnum mat.

What a delightful day with my colleagues!

Wooster’s Fossil of the Week: A ptilodictyine bryozoan from the Silurian of Ohio

May 15th, 2015

Phaenopora superba Brassfield 585The fossil above was found by Luke Kosowatz (’17) on our Sedimentology & Stratigraphy class field trip last month. We were measuring and sampling the Brassfield Formation (Early Silurian, Llandovery) near Fairborn, Ohio, and Luke pulled this beauty out of the rubble. This limestone is full of echinoderms and corals, so this lonely bryozoan was immediately a star.
Peela 050815This is the specimen that we sectioned and made an acetate peel from last month. The interior view, shown above, was critical to its identification. This peel was made perpendicular to the surface. It shows that the bryozoan is bifoliate, meaning it has two sides with zooids (the filter-feeding bryozoan polypides) and stood upright on the seafloor like a fan or leaf. Both sides had the characteristic bumps called monticules.
Phaenopora closerThe next critical view is this close-up of a slightly weathered surface of the bryozoan. It shows a regular arrangement of the larger zooecia (autozooecia) with two smaller zoooecia (metazooecia) between each pair. These clues enabled my friend Andrej Ernst, a paleontologist and bryozoan expert in the Department of Geosciences at the University of Hamburg, to identify this bryozoan as the ptilodictyine Phaenopora superba (Billings, 1866).
CNSPhoto-GEOLOGISTElkanah Billings (1820-1876) originally described this bryozoan species in 1866. He was Canada’s first government paleontologist, and he very much looked the part. Billings was born on a farm near Ottawa. He went to law school and became a lawyer in 1845, but he gave up dusty books for the life of a field paleontologist. In 1856 Billings joined the Geological Survey of Canada. He named over a thousand new species in his career. The Billings Medal is given annually by the Geological Association of Canada to the most outstanding of its paleontologists.


Billings, E. 1866. Catalogues of the Silurian fossils of the island of Anticosti: with descriptions of some new genera and species. Dawson brothers.

Ross, J.P. 1960. Larger cryptostome Bryozoa of the Ordovician and Silurian, Anticosti Island, Canada: Part I. Journal of Paleontology 34: 1057-1076.

Ross, J.P. 1961. Larger cryptostome Bryozoa of the Ordovician and Silurian, Anticosti Island, Canada: Part II. Journal of Paleontology 35: 331-344.

Wooster’s Fossil of the Week: A Jurassic coral with beekite preservation from southern Israel

May 8th, 2015

MicrosolenaCW366_585This week’s fossil is again in honor of Annette Hilton (’17), now retired as my Sophomore Research Assistant this year. She has been assessing with great skill a large and diverse collection of scleractinian corals from the Matmor Formation in Hamakhtesh Hagadol in the Negev Desert of southern Israel. These specimens were collected during paleoecological studies by the Wooster paleontology lab and our Israeli colleagues. Above is a fantastic specimen of Microsolena Lamouroux 1821. We are looking at the top of a gumdrop-shaped corallum, with the corallites (which held the polyps) as shallow pits with radiating septa.
MicrosolenaReverseBeekiteCW366_585This is the reverse view of the coral, showing its concentric growth lines. The jumble in the center is shelly debris on which the coral originally established itself on the muddy seafloor. Note that the preservation here includes numerous little circles. These are centers of silica replacement called beekite rings (a form of chalcedony).
BeekiteMicrosolenaReverseCW366_585Above is a closer view of the beekite preservation. The silica circles have concentric rings of their own. This kind of preservation (a type of silicification) is common in the Matmor Formation. Corals like this one started as aragonitic skeletons and then were replaced by calcite and silica. I suspect the calcitization took place first because of the fine degree of preservation for most of the corallum.
Henry Beeke (1751–1837)So how do we get a term like beekite? Meet Rev. Henry Beeke (1751-1837), a rather unlikely scholar to make it to this blog. Beeke was an Oxford graduate in divinity, with a strong concentration in history. He became a prestigious Regius Professor of Modern History at Oxford. He was sought after as an expert of economics and taxation at the beginning of the 19th Century. As with many divines of the time, Beeke also pursued natural history, specializing in botany. At some point in his career he was noted as having described what we now call beekite, but I can’t find where in the literature. All I have is a brief mention of “Beekite, a new mineral, named after Dr. Beeke, at the Corbors” in Blewitt (1832, p. 15). Henry Beeke had the distinction of seeing this mineral variety named after him during his lifetime, which is rare in science.


Blewitt, O. 1832. The panorama of Torquay: a descriptive and historical sketch of the district comprised between the Dart and Teign. Second edition. London: Simpkin and Marshall, 289 pages.

Church, A.H. 1862. XV. On the composition, structure, and formation of Beekite. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 23(152): 95-103.

Nose, M. and Leinfelder, R. 1997. Upper Jurassic coral communities within siliciclastic settings (Lusitanian Basin, Portugal): implications for symbiotic and nutrient strategies. Proceedings of the 8th International Coral Reef Symposium 2: 1755-1760.

Pandey, D.K., Ahmad, F. and Fürsich, F.T. 2000. Middle Jurassic scleractinian corals from northwestern Jordan. Beringeria 27: 3-29.

Pandey, D.K. and Fürsich, F.T. 2001. Environmental distribution of scleractinian corals in the Jurassic of Kachchh, western India. Journal Geological Society of India 57: 479-495.

Pandey, D.K. and Fürsich, F.T. 2005. Jurassic corals from southern Tunisia. Zitteliana 45: 3-34.

Wilson, M.A., Feldman, H.R., Bowen, J.C. and Avni, Y. 2008. A new equatorial, very shallow marine sclerozoan fauna from the Middle Jurassic (late Callovian) of southern Israel. Palaeogeography, Palaeoclimatology, Palaeoecology 263: 24-29.

Wilson, M.A., Feldman, H.R. and Krivicich, E.B. 2010. Bioerosion in an equatorial Middle Jurassic coral–sponge reef community (Callovian, Matmor Formation, southern Israel). Palaeogeography, Palaeoclimatology, Palaeoecology 289: 93-101.

Wooster’s Fossil of the Week: How to make brilliant acetate peels, with a Jurassic coral example

May 1st, 2015

1_Image_1986My retiring Sophomore Research student, Annette Hilton (’17), is excellent at making acetate peels. These peels, like the one above she made from a mysterious Callovian (Middle Jurassic) coral, show fine internal details of calcareous fossils and rocks.

2_Image_1987This is a closer view of the acetate peel of the coral showing incredible detail in the radiating septa and connecting dissepiments. This is a solitary coral from the Matmor Formation of southern Israel. We thought we knew what it was until we examined this peel and saw features we can’t match with any coral taxa. (Experts are invited to tell us what it is!) This view looks like it is from a thin-section, but it is all acetate and was made in about 20 minutes.

An acetate peel is a replica of a polished and etched surface of a carbonate rock or fossil mounted between glass slides for microscopic examination. Peels cannot give the mineralogical and crystallographic information that a thin-section can, but they are faster and easier to make. For most carbonate rocks most of the information you need for a petrographic analysis can be recovered from an acetate peel. In many paleontological applications, an acetate peel is preferred to a thin-section because you get essentially two dimensions without sometimes confusing depth.

To make a peel you need the following:

A trim saw for rock cutting.
A grinding wheel with diamond embedded disks (with 45µm and 30µm plates)
Grinding grit (3.0 µm) in a water slurry on a glass plate.
Acetate paper.
A supply of 5% hydrochloric acid in a small dish.
A supply of water in another small dish.
A squeeze bottle of acetone.
Glass biology slides (one by three inches)
Transparent tape.
A carbonate rock or fossil

We’re now going to show you how we make peels. This process was worked out by my friend Tim Palmer and me back in the 1980s. See the reference at the end of this entry.

DSC_5123Annette is in her required safety gear about to start the process by cutting a fossil. She needs to cut a flat surface that is usually perpendicular to bedding in a carbonate rock, or through a fossil at some interesting angle.

DSC_5124The specimen approaches the spinning diamond-embedded blade of the rock saw. Annette is holding the rock sample steady on a carriage she is pushing towards the blade. It is important to hold the specimen still as the blade cuts through it.

DSC_5126My camera is faster than I thought. Not only do you see those suspended drops of water, the spray is frozen in the air! The cut is almost complete.

DSC_5128Now we use a diamond-embedded grinding wheel (45 µm or 30 µm) to polish the surface cut with the saw. This will be the side from which we make the acetate peel.

DSC_5129A closer view of the rock (which contains an embedded bryozoan, by the way) being polished flat on the spinning wheel.

DSC_5130The best peels are made from surfaces that have the finest polish. We are using a 3.0 µm grit-water slurry on a glass plate to again polish the rock surface as smooth as possible, removing all saw and grinding marks.

DSC_5133Keep the plate wet and push down hard to polish the cut surface in the grit slurry. With carbonate rocks and fossils it takes no more than five minutes here to get an excellent polish.

DSC_5134Wash the specimen thoroughly in water to remove all grit. Check the polished surface for grinding marks. If you see any, return to the glass plate and slurry for more polishing.

DSC_5135We’re ready for the simple etching process. We use a Petri dish half-filled with 5% hydrochloric acid and a another dish with water. (Yes, I have a dirty hood in my lab.)

DSC_5136Annette is suspending the polished surface of the specimen downward into the acid bath. She dips it in only a couple millimeters or so. The acid reacts with the carbonate and fizzes. Her fingers are safely above the action, but if you’re nervous you can use tongs to hold the specimen. We usually keep the specimen in the acid for about 15 seconds, and then quench it with the water in the second dish. The etching time will vary with the strength of the acid and carbonate content of the specimen.

DSC_5140This is the kit you need to make the acetate peel itself. Note that we use a thin acetate rather than the thick sheets preferred by others.

DSC_5143The tricky part. When the specimen is dry, cut a piece of acetate somewhat larger than the etched surface. We then hold this acetate and the specimen in one hand, and the squeeze bottle of acetone in the other. The next step is to flood the etched surface, which is held flat and upwards, with the acetone and quickly place the acetate on the wetted surface. The acetate will adhere fast, so smooth it out with your fingers across the etched surface. At this point the acetone is partially dissolving the acetate, causing it to flow into the tiny nooks and crannies of the etched surface. The acetone evaporates and the acetate hardens into this microtopography.

DSC_5145If you did it correctly, you now have a sheet of acetate adhering entirely to the etched surface. With practice you learn how to avoid bubbles between the acetate and specimen. Opinions vary and how long to let the system thoroughly dry. We found that we can proceed to the next step in about five minutes.

DSC_5147Now you peel! Slowly and firmly pull the acetate off the specimen.

DSC_5152Carefully trim the acetate with scissors. Place this peel between two glass slides, squeeze tight, and seal the assemblage like a sandwich with transparent tape. You have now made an acetate peel. Easy!

DSC_5153Here’s our finished product. Twenty minutes from rock saw to peel. You’ll have to wait until another blog post to see what this particular peel shows us!


Wilson, M.A. and Palmer, T.J. 1989. Preparation of acetate peels. In: Feldmann, R.M., Chapman, R.E. and Hannibal, J.T. (eds.), Paleotechniques. The Paleontological Society Special Publication 4: 142-145. [The link is to a PDF.]