Archive for April, 2015

Wooster’s Fossil of the Week: A twisted scleractinian coral from the Middle Jurassic of southern Israel

April 24th, 2015

1 Epistreptophyllum Matmor CW366 585Another exquisite little coral this week from the collection of Matmor Formation (Middle Jurassic, southern Israel) corals Annette Hilton (’17) and I are working through. We believe this is Epistreptophyllum Milaschewitsch, 1876. It is a solitary (although more on that in a moment) scleractinian coral found in marly sediments at our location C/W-366 in Hamakhtesh Hagadol. I’m always impressed at how well preserved these corals are considering their original aragonitic skeletons were replaced long ago.
2 Epistreptophyllum lateral bentOne cool thing about this specimen is the near 90° bend it took during growth. Apparently it was toppled over midway through its development but survived and grew a twist so it could keep its oral surface (where the polyp resided) upwards. Another interesting observation is the small bud visible near the base. Gill (1982) suggested that the solitary Epistreptophyllum in the Jurassic of Israel may have been able to branch into separate individuals. Pandey and Lathuilière (1997) doubted this and suggested that Gill had misidentified his Israeli specimens. Maybe so, but we’re pretty sure we have Epistreptophyllum here, and we definitely have budding. We’re always open to other ideas!
3 Epistreptophyllum orientedHere is another view of the specimen in its living position after the fall. I love the sweep of the vertical ribs as it made the bend.
4 Epistreptophyllum septaTo complete the tour of this specimen, here’s a view of the oral surface where the polyp lived. The radiating lines are the septa that extended vertically through the interior of the corallite.
5 Milaschewitsch plate 50Epistreptophyllum was named in 1876 by Constantin Milaschewitsch. Here is Plate 50 from that massive work. Epistreptophyllum is marked by the red rectangles. (Note the misspelling of the genus in the caption for figure 2.) I wish I knew more about Mr. Milaschewitsch, but his particulars are thus far not available. I can tell he worked in Moscow and St. Petersburg, Russia, but that’s all. If anyone knows more about this man, please add your information in the comments.

References:

Gill, G.A. 1982. Epistreptophyllum (Hexacorallaire Jurassique), genre colonialou solitaire? Examen d’un matériel nouveau d’Israel. Geobios 15: 217-223.

Milaschewitsch, C. 1876. Die Korallen der Nattheimer Schichten. Palaeontographica 21: 205-244.

Pandey, D.K. and Lathuilière, B. 1997. Variability in Epistreptophyllum from the Middle Jurassic of Kachchh, western India: an open question for the taxonomy of Mesozoic scleractinian corals. Journal of Paleontology 71: 564-577.

Flipping the Classroom with Meteorite Impacts

April 21st, 2015

Our introductory courses don’t have labs, but that doesn’t stop our students from having hands-on experiences. Today, students in the Geology of Natural Hazards investigated the relationship between impact craters and projectile properties (size, mass, velocity) by experimenting with a tray of sand and a variety of projectiles. Students had a marble, ping pong ball, golf ball, and tennis ball that they could use to run experiments that would help them understand the factors that control the size and appearance of impact craters.

Students made craters by dropping the projectiles from a known height into the sand trays.

Students made craters by dropping the projectiles from a known height into the sand trays.

They repeated the experiment for a range of heights above the sand.

They repeated the experiment for a range of heights above the sand.

They measured the depth and diameter of each crater formed, and used their data to come up with the relationship between the size of the crater, the size and mass of the projectile, and the velocity.

They measured the depth and diameter of each crater formed, and used their data to come up with the relationship between the size of the crater, the size and mass of the projectile, and the velocity.

One group managed to conduct their experiments outside, although the brisk spring breeze introduced some error into their ping pong ball measurements!

One group managed to conduct their experiments outside, although the brisk spring breeze introduced some error into their ping pong ball measurements!

To prepare for today’s class, the students completed an online reading quiz. We reviewed questions from the reading quiz at the start of class, then covered the experiment setup. Students had the remaining period to work on their experiments. Some groups completed the assignment in class while others will need some more time to finish plotting their data. We’ll go over their results in our next class meeting.

A beautiful day for Wooster Geologists in the Silurian of Ohio

April 18th, 2015

aDSC_5072FAIRBORN, OHIO–It’s field trip season at last for the Wooster Geologists. Several geology classes have now been out in Ohio, taking advantage of windows of spectacular weather. Today was one of those days for 25 students in the Sedimentology & Stratigraphy class. We returned to the Oakes Quarry Park exposures in southwestern Ohio (N 39.81472°, W 83.99471°). Three years ago here in April it was 37°F and raining. This year the conditions were perfect. We studied outcrops of the Brassfield Formation (Early Silurian, Llandovery) in the old quarry walls. The students measured stratigraphic columns of these fossiliferous biosparites as part of an exercise, and then explored the glacially-truncated top of the unit.

bDSC_5079The Brassfield is intensely fossiliferous. Large portions of it are virtually made of crinoid fragments. In the random view above you can see columnals, as well as a few calyx plates. This is why this unit is very popular among my echinodermologist friends at Ohio State.

DSC_5056Kevin Komara, Brian Merritt and Dan Misinay (Team Football) are here contemplating the quarry wall, planning how to measure their sections.

DSC_5063One of our Teaching Assistants, Sarah Bender, is here pointing out one of the many thin intercalated clay units in the Brassfield biosparites.

DSC_5065Fellow Californian Michael Williams directed the action. No, actually he’s doing the time-honored technique of following a measured unit with his finger as he finds a place he can safely climb to it and the units above. He is holding one of our measuring tools, a Jacob’s Staff. Why do we call them “Jacob’s Staffs”? Read Genesis 30:25-43. (Yes, today’s students are mystified by Biblical references.)

DSC_5066Here’s Rachel Wetzel, giving me a heart attack. Don’t worry, insurance companies and parents, she’s fine.

DSC_5068Rachel is again on the left. Team Ultimate Frisbee (Meredith Mann and Mae Kemsley) are in the front, and Sharron Ostermann is above. This is the recommended way to get to the top of the exposure!

DSC_5070We carried our lunches in “to go” boxes from the dining hall. Our Teaching Assistants Sarah Bender and Kaitlin Starr enjoyed a sunny picnic on the rocks.

yDSC_5077The top level of the quarry was cleared of soil and brush many years ago to expose a glacially truncated and polished surface of the Brassfield. Looking for glacial grooves and fossils here are (from the left) Tom Dickinson, Jeff Gunderson (another Californian!), Andrew Conaway, and Luke Kosowatz (who seems to also be making a little pile of rocks as a memorial to a great day).

zDSC_5074One of the many corals we found in the top of the Brassfield was this halysitid (“chain coral”), an indicator fossil for the Late Ordovician and Silurian.

Everyone returned safely to Wooster with their completed stratigraphic columns, lithological descriptions, and a few fossils. Thank you to Mark Livengood, our bus driver. Good luck to the other field trip groups later this month!

Geomorphology at Fern Valley and along the Little Killbuck

April 12th, 2015

group_fernThe group at Fern Valley. Gaging Wilkin Run and measuring water levels in wells. We are fortunate to be able to monitor the streamflow, climate and geomorphic changes along Wilkin Run. Thanks again to Betty and David Wilkin for donating Fern Valley to the College.

leo_icsdLeo examining the Ice Contact stratified drift of the terminal moraine that in part lies across Fern Valley. This deposit records the Laurentide’s ice sheet advance into the proglacial Odell Lake (note the gray lacustrine clays and silts to Leo’s left). The exposure is capped with loess – the parent material of the soils here.

wellA well installed in the middle of the Run indicates whether the stream is gaining or losing. It is confusing at first.

gagingThe Archaeology team measures the velocity profile at Fern Valley. Note the terrace in the background, most of this sediment is eroded soils – likely introduced over the past few hundred years – so-called Legacy sediments.

deltaDescribing the stratigraphy along the Little Killbuck Valley – this is a delta – topsets (note the channel fills at the top) and foresets (The students are standing on the foreset beds, the foresets are muddy and weathered because the local bedrock is weathered shale and there was some rain falling that day) – the bottomsets are shown below.

lacustrineThe bottomset beds – gray silts to the right.  Jim navigates a modern mudflow fan on his way to the colluvium that  lies above the bedrock contact.

Wooster’s Fossil of the Week: A tectonically-deformed Early Cambrian trilobite from southeastern California

April 10th, 2015

Olenellus terminatus whole 585This wonderful trilobite was found last month by Olivia Brown (’15), a student on the Wooster Geology Department’s glorious field trip to the Mojave Desert. Olivia collected it at Emigrant Pass in the Nopah Range of Inyo County, southeastern California. It comes from the Pyramid Shale Member of the Carrara Formation and is uppermost Lower Cambrian. It appears to be the species Olenellus terminatus Palmer, 1998. It is a great specimen because most of the body segments are still in place. At this locality we find mostly the semi-circular cephalon (the head) separated from the rest of the body. The species O. terminatus is so named because it represents the last of its famous lineage of Early Cambrian trilobites. The last time we found such a whole trilobite at this site was in 2011, with Nick Fedorchuk as the paleo star of the day.

This trilobite has been tectonically strained along its main axis, giving it a narrow look it did not possess in life. In fact, these trilobites with their semi-circular cephala make nice indicators of the strain their hosting rocks have experienced.
spines 032515 585This particular kind of trilobite has very distinctive spines, as shown in the close-up above. The long spine on the right comes from the trailing edge of the cephalon and is called a genal spine. The one in the center is a thoracic spine emerging from the third thoracic segment. The primary role of these spines was probably the obvious one: protection from predators. They may also have helped spread the weight of the animal across the substrate if they were walking across soupy mud (much like a snowshoe).

We’ve met this man before in this blog. James Hall (1811–1898) named the genus Olenellus in 1861. 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), an American who learned his geology from Benjamin Silliman (1779-1864) at Yale. 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 my academic link to old man Hall above.

References:

Adams, R.D. 1995. Sequence-stratigraphy of Early-Middle Cambrian grand cycles in the Carrara Formation, southwest Basin and Range, California and Nevada, p. 277-328. In: Sequence Stratigraphy and Depositional Response to Eustatic, Tectonic and Climatic Forcing. Springer Netherlands.

Cooper, R.A. 1990. Interpretation of tectonically deformed fossils. New Zealand Journal of Geology and Geophysics 33: 321-332.

Hazzard, J.C. 1937. Paleozoic section in the Nopah and Resting Springs Mountains, Inyo County, California. California Journal of Mines and Geology 33: 273-339.

Palmer, A.R. 1998. Terminal Early Cambrian extinction of the Olenellina: Documentation from the Pioche Formation, Nevada. Journal of Paleontology 72: 650–672.

Palmer, A.R. and Halley, R.B. 1979. Physical stratigraphy and trilobite biostratigraphy of the Carrara Formation (Lower and middle Cambrian) in the southern Great Basin. U.S. Geological Survey Professional Paper 1047: 1-131.

Shah, J., Srivastava, D.C., Rastogi, V., Ghosh, R. and Pal, A. 2010. Strain estimation from single forms of distorted fossils—A computer graphics and MATLAB approach. Journal of the Geological Society of India 75: 89-97.

Wooster’s Fossil of the Week: A disturbingly familiar coral from the Middle Jurassic of southern Israel

April 3rd, 2015

Single Axosmilia side 585Our fossil this week is one I don’t share with my Invertebrate Paleontology classes until they’re ready for it. Those of us who grew up with Paleozoic fossils think we recognize it right away. Surely this is a solitary rugose coral? It has the right shape and the fine growth lines we call rugae (think “wrinkles”). This view below of the oral surface is not surprising either, unless you’re an enthusiast of septal arrangements.
Axosmilia oral view 585Instead of a rugose coral, though, this is a scleractinian coral from the Matmor Formation (Middle Jurassic, Callovian) of Hamakhtesh Hagadol, Israel. It is part of the collection of Matmor corals Annette Hilton (’17) and I are working through. This coral belongs to the genus Axosmilia Milne Edwards, 1848.
Axosmilia group 031815 585These corals are excellent examples of evolutionary convergence. The scleractinians are only very distantly related to the rugosans. They do not share a common ancestor with a calcareous skeleton, let alone a cone-shaped one like this. Instead the scleractinians like Axosmilia developed a skeleton very similar to that of the solitary rugosans, probably because they had similar life modes in similar environments, and thus similar selective forces. The rugosans, though, built their skeletons out of the mineral calcite, whereas the scleractinians use aragonite. (This specimens are calcite-replaced, like our specimen last week.) The vertical septa inside the cone are also arranged in different manners. Rugosans insert them in cycles of four (more or less), giving them a common name “tetracorals”; scleractinians have septal insertions in cycles of six, hence they are “hexacorals”. Rugose corals went extinct in the Permian; scleractinians are still with us today. Our friend Axosmillia appeared in the Jurassic and went extinct in the Cretaceous.

Rugose coral skeletons in the Paleozoic are commonly encrusted with a variety of skeletal organisms, and many are bored to some degree. I expected to see the same sclerobionts with these Jurassic equivalents, but they are clean and unbored. I suspect this means they lived semi-infaunally (meaning partially buried in the sediment).
Henri Milne-Edwards (1800–1885)Axosmilia was named by the English-French zoologist Henri Milne-Edwards (1800-1885) in the politically complex year of 1848. Henri was the twenty-seventh (!) child of an English planter from Jamaica and a Frenchwoman. He was born in Bruges, which is now part of Belgium but was then under the control of revolutionary France. Like many early 19th century scientists, Milne Edwards earned an MD degree but was seduced away from medicine by the wonders of natural history. He was a student of the most accomplished scientist of his time, Georges Cuvier, and quickly became a published expert on an amazing range of organisms, from crustaceans to lizards. The bulk of his career was spent at the Muséum National d’Histoire Naturelle in Paris. When he was 42 he was elected a foreign member of the Royal Society, receiving from them the prestigious Copley Medal in 1856. He died in Paris at the age of 85.

References:

Fürsich, F.T. and Werner, W. 1991. Palaeoecology of coralline sponge-coral meadows from the Upper Jurassic of Portugal. Paläontologische Zeitschrift 65: 35-69.

Martin-Garin, B., Lathuilière, B. and Geister, J. 2012. The shifting biogeography of reef corals during the Oxfordian (Late Jurassic). A climatic control?. Palaeogeography, Palaeoclimatology, Palaeoecology 365: 136-153.

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. 2005. Jurassic corals from southern Tunisia. Zitteliana 45: 3-34.