Archive for the 'Uncategorized' Category

Wooster Geologists in San Diego, CA

May 20th, 2016

San Diego, CA – Wooster Geologists don’t waste any time getting to work on their summer research. Amineh AlBashaireh (’18) and I have made our way to the University of San Diego to start on a new research project with our collaborators in the Department of Environmental and Ocean Sciences. Our trip began with a tour of the department’s facilities in the impressive Shiley Center for Science and Technology.

The grand and welcoming entrance to the Shiley Center, which houses USD's science programs.

The grand and welcoming entrance to the Shiley Center, which houses USD’s science programs.

Visitors to the Department of Environmental and Ocean Sciences are greeted with this stunning display of a donated coral collection.

Visitors to the Department of Environmental and Ocean Sciences are greeted with this stunning display of a donated coral collection.

A favorite lunch spot is the Strata Plaza. The plaza was designed to represent the local stratigraphy and includes regional fossils, stones, and shells.

A favorite lunch spot is the Strata Plaza. The plaza was designed to represent the local stratigraphy and includes regional fossils, stones, and shells.

Our tour ended in the lab, where Dr. Bethany O'Shea and her graduate student, Elizabeth Johnston, gave us an overview of their work. Looks like they mean business!

Our tour ended in the lab, where Dr. Bethany O’Shea and her graduate student, Elizabeth Johnston, gave us an overview of their work. Looks like they mean business!

We’re looking forward to a full week of field and lab work. Stay tuned for more posts from sunny San Diego!

Wooster’s Fossil of the Week: A phyllocarid crustacean from the Middle Cambrian Burgess Shale of British Columbia, Canada

May 20th, 2016

Canadaspis perfecta Burgess Shale 585We are fortunate at Wooster to have a few fossils from the Burgess Shale (Middle Cambrian) collected near Burgess Pass, British Columbia, Canada, including this delicate phyllocarid Canadaspis perfecta (Walcott, 1912). This species is one of the oldest crustaceans, a group that includes barnacles, crabs, lobsters and shrimp. Please note from the start that I did NOT collect it. The Burgess Shale is a UNESCO World Heritage Site, so collecting there is restricted to a very small group of paleontologists who have gone through probably the most strict permitting system anywhere. I had a wonderful visit to the Burgess Shale with my friend Matthew James in 2009, and we followed all the rules. (The photo below is of the Walcott Quarry outcrop.) Our Wooster specimen was in our teaching collection when I arrived. I suspect it was collected in the 1920s or 1930s and probably purchased from a scientific supply house.

walcottquarryMarrellaSuch a dramatic setting, which is perfect for the incredible fossils that have come from this site.

Canadaspis perfecta drawing

Canadaspis perfecta has been thoroughly studied by Derek Briggs, the most prominent of the paleontologists who have studied the Burgess Shale fauna. The above reconstruction of C. perfecta is from his classic 1978 monograph on the species. He had spectacular material to work with, including specimens with limbs and antennae well represented. Our specimen is a bit shabby in comparison! Nevertheless, we can still make out abdominal segments and a bit of the head shield.

Briggs (1978, p. 440) concluded that C. perfecta likely “fed on coarse particles, possibly with the aid of currents set up by the biramous appendages”. This is a similar feeding mode to many of the trilobites who lived alongside.

References:

Briggs, D.E. 1978. The morphology, mode of life, and affinities of Canadaspis perfecta (Crustacea: Phyllocarida), Middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 281: 439-487.

Briggs, D.E. 1992. Phylogenetic significance of the Burgess Shale crustacean Canadaspis. Acta Zoologica 73: 293-300.

Wooster’s Fossil of the Week: A Recent Sponge Boring from South Carolina

May 13th, 2016

1 Coral on bored bivalveWe’re not actually looking at fossils here, but this bivalve-coral-sponge assemblage from the very modern Myrtle Beach in South Carolina is to cool not to share. Jacob Nowell (Wooster ’18) picked it up while on Spring Break this year and donated it to the collections. This is a bit of very worn bivalve shell punctured by clionaid sponge borings and encrusted by a columnar scleractinian coral.

2 Bored bivalve hingeHow do we know the shell remnant is from a bivalve? This is what’s left of the hinge region, the thickest part of the shell. We can tell this is a heterodont bivalve, probably of the common genus Mercenaria. The shell material is calcite.

3 Coral over EntobiaThe coral is aragonitic and exquisitely preserved. It did not make the long tumbling journey the bivalve shell did. At its encrusting base you can see that it partially covers some of the sponge borings, showing that it attached after the sponge was at least partly gone. The round structures on the coral are the corallites, each of which housed a coral polyp. The corallites have radiating vertical septa inside in the classic scleractinian manner.

4 Entobia gallery 041316 585The sponge boring is the star here. This is a side view showing the interconnected galleries and tunnels excavated by a clionaid sponge like Cliona. As a trace fossil this structure would be known as Entobia. It is very common in the fossil record, especially in the Cretaceous and later.

Bronn 041616Entobia was named and 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. He didn’t fully accept “Darwinism” at the end of his life, but he made the first translation of On The Origin of Species into German.

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. Letkaea 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.

 

A Wooster Geologist Visits Spangler Park

May 9th, 2016

Chloe1Editor’s note: The following entry was written by Chloe Wallace (’17), a student in this year’s Sedimentology & Stratigraphy course. One of our writing assignments was to write a blog post about our recent field trip to Spangler Park (also known as Wooster Memorial Park). I told the class that I would publish on this site the best entry, and Chloe won. It was a very close contest, though, with many other excellent entries. All the following words and images are Chloe’s.

Wooster, Ohio— On April 23, 2016, the Sedimentology and Stratigraphy class took a field trip to the local Wooster Memorial Park, also called Spangler Park. The goal was to study three separate outcrops, and then do a little exploring of our own.

The first stop was a short walk from the entrance to the park, specifically at 40.81475° North and 82.02383° West (above).

This outcrop contains rocks from the Logan Formation of the Lower Carboniferous. The rocks were non-laminated and of silt size, so it is made of siltstone. There are signs of a little bit of oxidation. There are also ripples present on some of the rocks, which is evidence of a shallow water environment. There were gray shale clasts within the siltstone, which were most likely deposited by storm events. The fact that some of the beds are thicker than others is more evidence of storm events because more sediment would have been deposited during storms and thinner beds would have built up during times of less activity. The bedding angles vary throughout the outcrop, also known as cross-stratification, which is more evidence that ripples and dunes were present as part of a flow regime at the time of deposition.

Chloe2Burrow fossils, which are a form of trace fossil, were left behind by deposit feeding organisms on some of the rocks. This is more evidence of a shallow, marine environment. Based on all the sedimentary structures and characteristics found at this outcrop, these rocks were deposited on the shallow shelf, below the fair weather wave base and above the storm wave base.

The Logan Formation is made up of five members, but specifically the Byer member is likely exposed here. Layers of fine sandstone and siltstones with shale sometimes inter-bedded characterize the Byer member (Hunt, 2009). Although it isn’t present in the two photos above, another member is usually deposited right below the Byer Member. It is called the Berne Member and it is composed of molasse rock, which is a quartz-rich conglomerate formed when the eroded material from continental collisions gathers in a foreland basin. In this case it is eroded material from the continental collisions that built up the Appalachians. The eroded material was then deposited to the west in the foreland basin that covers Pennsylvania and Ohio.

The second outcrop we reached was at the bottom of a gorge, along Rathburn Run, specifically at 40.81784° N and 82.02946° W. The exposure was composed of laminated grey shale from the Cuyahoga Formation. It marked a formation boundary because Logan Formation sandstone lies directly above it. This means the grey shale is older than the Logan Formation. Similar to the Logan Formation, there are trace fossils of marine burrowing organisms within the shale.

Chloe3In the above picture you can see an East-West trending joint running through the center of the Cuyahoga Formation grey shale caused by tectonic faulting, which is a phenomenon unrelated to the sedimentary structures.

Chloe4Siderite deposits were also found in some sandstone at the Rathburn run outcrop, which form after deposition, a diagenetic property. Siderite forms in anoxic environments where iron is reduced and sulfur is present. The grey shale of the Cuyahoga Formation isn’t porous enough for siderite replacement to take place, but the sandstone is.

The third outcrop was father upstream along on a cut bank, located at 40.81903° N and 82.02953° W.

Chloe5This photo is taken from across Rathburn Run, from the point bar. This outcrop is much younger in age, from the last time Ohio was affected by glaciation. During the Last Glacial Maximum, specifically the Pleistocene, glacial debris flows deposited the bottom section of the outcrop. The sediment is characterized by a fining upwards sequence and has two scales of support. Some areas of the deposit are composed of large grains within a matrix-support due to debris flow. Other areas of the deposit are composed of sandy conglomerate rock that is grain supported. Overall the sediment is poorly sorted and contains glacial erratics within the sediment, including boulders made of gneiss, granite, and some sedimentary rocks.

A channel cut through the original glacial debris flow deposit and was eventually filled in by wind-blown silt, also known as loess. Loess is characteristically different from the glacial deposit at the bottom of the outcrop. Loess breaks in sheets, which causes it to have steep angles. Overall, the history of this outcrop is that approximately 15,000 years ago debris flow events deposited the glacial sediment at the bottom of the outcrop, then a channel cut into the deposit and that channel eventually filled with eolian (wind-blown) silt.

Chloe6After venturing a little on our own, a few other students and myself came across a fourth outcrop that was from the Logan Formation at an elevation above both the Cuyahoga Formation shales and the glacial deposits. There is more evidence of jointing and cross-stratification that can be seen in the picture.

We saw two separate formations from the Lower Carboniferous during the field trip. We also were able to see another type of sedimentary deposit that was glacial and eolian in origin. Spangler Park displays and exposes a variety of sedimentary structures and sedimentary characteristics. The park can be characterized as displaying a coarsening upwards sequence with the Cuyahoga shale at the bottom, followed by the coarser siltstone and sandstone of the Logan Formation. This kind of coarsening upwards is usually evidence of either regression or progradation.

Both the Logan and Cuyahoga Formations are representative of shallow marine environments, as was seen in the evidence found at Spangler. Further research shows that the Cuyahoga Formation was deposited as part of a marine environment where the shoreline was prograding during the Kinderhookian and possibly very early Osagean (Bork and Malcuit, 1979; Matchen and Kammer, 2006). The Logan Formation followed and was deposited within a marine proximal deltaic environment during the Osagean (Hunt, 2009; Matchen and Kammer, 2006). This explains the coarsening upwards sequence and the marine sedimentary structures and fossils seen throughout the field trip.

References:

Bork, K.B., and Malcuit, R., 1979, Paleoenvironments of the Cuyahoga and Logan Formations (Mississippian) of central Ohio: Geological Society of America Bulletin II, v. 90, p. 1782-1838.

Hunt, H., 2009, Paleocommunities and Paleoenvironments of the Logan Formation (Mississippian, Osagean) of northeastern Ohio [Undergraduate thesis]: Wooster, The College of Wooster, 50 p.

Matchen, D.L., and Kammer, T.W., 2006, Incised valley fill interpretation for Mississippian Black Hand Sandstone, Appalachian Basin, USA: Implications for glacial eustasy at Kinderhookian-Osagean (Tn2-Tn3) boundary: Sedimentary Geology, v. 191, 89-113.

Wooster’s Fossil of the Week: A craniid brachiopod from the Upper Cretaceous of The Netherlands

May 6th, 2016

1 Isocrania costata Sowerby 1823 double 2 smThese striking little brachiopods are gifts from Clive Champion, a generous Englishman with whom I occasionally exchange packets of fossils. In January I received a surprise box with lots of delicious little brachs, including the two shown above. I remember this type well from a field trip I had to the Upper Cretaceous of The Netherlands.
2 Isocrania costata Sowerby 1823 double 1 smHere we see the reverse sides of the shells at the top. These are most likely dorsal valves of Isocrania costata Sowerby, 1823, from the Lichtenberg Horizon, Upper Maastrichtian (Upper Cretaceous) of the ENCI Quarry near Maastricht, The Netherlands. It is possible they are the closely-related species Isocrania sendeni Simon, 2007, but we don’t have enough material to sort this out.
4 Surlyk 1973 fig 2 copyCraniid brachiopods usually live out their lives attached to hard substrates, as with this Ordovician example. This species of Isocrania, however, was only attached to shelly debris on the seafloor for a short time, outgrowing its substrate early and then living free in the chalky sediment. The above reconstruction image is Figure 2 from Surlyk (1973).

Christian Emig (2009) has a bit of folklore about Isocrania. In medieval Sweden these fossils were called “Brattingsborg pennies” for their size, shape and the face-like image on their interiors. Don’t see the face? Check this out from Emig (2009):
5 Ventral C craniolaris fig 6 SurlykThe “eyes” in this ventral valve are large adductor muscle scars, and the “mouth” and “nose” are a smaller set. Here is one of the “Brattingsborg pennies” legends Emig (2009) relates —

“… at the beginning of the 13th century the archbishop Anders Sunesen spent his last days on the island of Ivö, in his own castle of which the cellar was about 2 km southeast of the castle. In 1221, subjected to the terminal stages of leprosy, he spent his last days on the island. One day he was informed that warriors had stolen a large sum of money from the Brattingsborg castle. They spent that night gambling and carousing in the cellar. The archbishop cursed this money and the following morning the warriors were stunned to find that the coins had turned into stones with a laughing death’s-head on them.”

Thanks for starting us on this trip with your gift, Clive!
3 Isocrania costata Sowerby 1823 sm
References:

Emig, C. 2009. Nummulus brattenburgensis and Crania craniolaris (Brachiopoda, Craniidae). Carnets de Géologie/Notebooks on Geology, Brest, Article, 8.

Hansen, T., and Surlyk, F. 2014. Marine macrofossil communities in the uppermost Maastrichtian chalk of Stevns Klint, Denmark. Palaeogeography, Palaeoclimatology, Palaeoecology 399: 323-344.

Simon, E. 2007. A new Late Maastrichtian species of Isocrania (Brachiopoda, Craniidae) from The Netherlands and Belgium. Bulletin de l’Institut royal des Sciences naturelles de Belgique, Sciences de la Terre 77: 141-157.

Surlyk, F. 1973. Autecology and taxonomy of two Upper Cretaceous craniacean brachiopods. Bulletin of the Geological Society of Denmark 22: 219-242.

Wooster Geologists in the 2016 Wooster Senior Research Symposium

April 29th, 2016

Michael Williams 042916WOOSTER, OHIO–A dozen Wooster Geologists participated today in the annual Wooster Senior Research Symposium: A Celebration of Independent Study! All did superb presentations that were very well received. The geology portion began in the morning with talks from Team Utah 3.0, led by Dr. Meagen Pollock and Dr. Shelley Judge. Michael Williams (’16) gave his talk entitled “Emplacement Processes and Monogenetic Classification of Ice Springs Volcanic Field, Central Utah”. Here’s a link to Michael’s field work.

Kelli Baxstrom 042916Kelli Baxstrom (’16) also spoke for Team Utah with her talk entitled: “Ice Springs Volcanic Field: New Insights and History for a Series of Complex Eruptions”. Here’s a link to Kelli’s field work.

Maddie Happ 042916Maddie Happ (’16) had a poster entitled: “Investigating Blue Light Intensity in Tree Rings to Generate High-Sensitivity Summer Temperature Records for Southern Alaska”. Here’s a link to Maddie’s field work.

Mae Kemsley 042916Mae Kemsley (’16) presented: “An isotopic analysis of belemnites from the Speeton Clay Formation (Lower Cretaceous) of Filey Bay, North Yorkshire, England”. Here’s a link to Mae’s field work.

Meredith Mann 042916Meredith Mann (’16) gave a poster entitled: “Paleoecology and Depositional Environments of the Passage Beds Member at Filey Brigg (Upper Jurassic, North Yorkshire, England)”. Here’s a link to Meredith’s field work.

Dan Misinay 042916Dan Misinay (’16) presented: “Late Holocene Glacial History of Muir Inlet, Glacier Bay National Park and Preserve, Alaska”. Here’s a link to Dan’s field work.

Brittany Nicholson 042916Brittany Nicholson (’16) gave a poster entitled: “Mentoring Structures in Undergraduate Research”.

Eric Parker 042916Eric Parker (’16) presented: “Analysis of Water Quality Parameters and Preliminary Investigation into the Impacts of Human Access on the Water Quality of the Nisqually River, Mount Rainier National Park”.

Krysden Schantz 042916Krysden Schantz (’16) gave: “The Use of Multiple Dating Methods to Determine the Age of Basalt in the Ice Springs Volcanic Field, Millard County, Utah”. Here’s a link to Krysden’s field work.

Adam Silverstein 042916Adam Silverstein (’16) presented: “Regional Volcanic Extinction as a Mechanism for Subsidence in the Vatnsdalur Structural Basin, Skagi Peninsula, Northwest Iceland”. You can find Adam in Iceland in this post.

Kaitlin Starr 042916Kaitlin Starr (’16) is a double major in studio art and geology. Maybe we shouldn’t have been surprised to see her double-booked for the same time slot at the symposium. Her geology I.S. thesis poster was titled: “Reconstructing Glacial History from Forests Preserved in the Wake of the Catastrophic Retreating Columbia and Wooster Glaciers, Prince William Sound, Alaska”. Here’s a link to Kaitlin’s field work. She is shown above with her art exhibit: “Exploring the Unknown: A Ceramic Journey Through the Sea of Imagination”. She made fantastical representations of marine creatures that do not exist but look eerily like beautiful fossils.

Kaitlin Kreation III call them Kaitlin’s Kreations, and think they’re wonderful!

Congratulations on your successful Independent Study projects, Wooster Seniors!

Wooster’s Fossil of the Week: A terebratulid brachiopod from the Middle Jurassic of northwestern France

April 29th, 2016

1 Cererithyris arkelli Almeras 1970 dorsal 585We have another beautiful brachiopod this week from our friend Mr. Clive Champion in England. He sent me a surprise package of fossils earlier this year. They are very much appreciated by me and my students!

The specimen above is Cererithyris arkelli Almeras, 1970, from the Bathonian (Middle Jurassic) of Ranville, Calvados, France. (Ranville, by the way, was the first village liberated in France on D-Day.) It is a terebratulid brachiopod, which we have seen before on this blog from the Miocene of Spain and the Triassic of Israel. They have the classic brachiopod form. The image above shows the dorsal valve with the posterior of the ventral valve housing the round hole for the fleshy stalk (pedicle) it had in life.
2 Cererithyris arkelli Almeras 1970 sideThis is a side view of C. arkelli. The dorsal valve is on the top; the ventral valve on the bottom. It is from this perspective that brachiopods were called “lamp shells” because they resemble Roman oil lamps.
3 Cererithyris arkelli Almeras 1970 ventralThis is the ventral view of the specimen. These brachiopods are remarkably smooth.
4 William_Joscelyn_ArkellCererithyris arkelli was named by Almeras (1970) in honor of William Joscelyn Arkell (1904–1958). Arkell was an English geologist who essentially became Dr. Jurassic during the middle part of the 20th Century. I’m shocked to see that with all his publications, awards and accomplishments, he died when he was only 54 years old.

W.J. Arkell grew up in Wiltshire, the seventh child of a wealthy father (a partner in the family-owned Arkell’s Brewery) and artist mother (Laura Jane Arkell). He enjoyed nature as a child, winning essay contests on his observations of natural history in his native county and south on the Dorset coast. Arkell was unusually tall for his age (6 feet 4.5 inches by age 17.5 years in an unusually detailed note) and was considered to have “outgrown his strength”. Nature and writing were escapes from athletic events. He also published poems.

Arkell attended New College, Oxford University, intending to become an entomologist, but Julian Huxley was his tutor and he quickly adopted geology and paleontology. Eventually he earned a PhD at Oxford in 1928, concentrating his research on Corallian (Upper Jurassic) bivalves of England. As a side project, he published work on Paleolithic human skeletons from northern Egypt.

Oxford suited Arkell, so he stayed there as a research fellow, expanding his research to the entire Jurassic System of Great Britain, then Europe, and then the world. His work became the standard for understanding Jurassic geology and paleontology for decades.

After World War II (in which he served in the Ministry of Transport), Arkell took a senior research position at Trinity College and the Sedgwick Museum, Cambridge University, continuing his work on the Jurassic. He travelled often, including long stints in the Middle East. His health was never good, though, and he had a stroke in 1956, and died after a second stroke in 1958.

During his career Arkell received the Mary Clark Thompson Medal from the National Academy of Sciences in the USA, a Fellowship in the Royal Society, the Lyell Medal from the Geological Society of London, and the Leopold von Buch medal from the German Geological Society.

References:

Almeras, Y. 1970. Les Terebratulidae du Dogger dans le Mâconnais, le Mont dʼOr lyonnais et le Jura méridional. Étude systématique et biostratigraphique. Rapports avec la paléoécologie. Documents des Laboratoires de Géologie Lyon, 39, 3 vol.: 1-690.

Arkell, W.J. 1956. Jurassic Geology of the World. New York; Edinburgh: Hafner Publishing Co; Oliver & Boyd; 806 pp.

Cox, L.R. 1958. William Joscelyn Arkell 1904-1958. Biographical Memoirs of Fellows of the Royal Society 4: 1.

Rousselle, L. and Chavanon, S. 1981. Le genre Cererithyris (Brachiopodes, Terebratulidae) dans le Bajocien supérieur et le Bathonien des Hauts-Plateaux du Maroc oriental. CR somm. Soc. Géol France, 1981: 89-92.

Sedimentology & Stratigraphy class in Wooster Memorial Park. Watch this space!

April 23rd, 2016

1 Glacial 042316This morning Wooster’s Sedimentology & Stratigraphy class visited Wooster Memorial (“Spangler”) Park for some field experience. A few of the students are shown above exploring a magnificent glacial deposit. I never did get a photo with all 21 students in it.

2 Logan Rathburn RunThe students are each writing a blog entry about the geology of this park as a writing assignment. You can see the instructions and additional images on our course page. The best entry will soon be posted in this blog under the student’s name. Above is a nice stream-side outcrop of the Logan Formation (Lower Carboniferous).

3 Trillium trail 042316It was a chilly but mercifully dry day for us. Classic early spring foliage for northeastern Ohio. [Dr. Lyn Loveless, our expert botanist, comes through in the comments: “Classic Spring Foliage – mostly (it seems from this scale) Dutchman’s Breeches, Dicentra cucullaria.  One stray Trillium.  Ah, Spring in Ohio!”]

4 Trillium grandiflorum 042316 585The most noteworthy flower this week is Trillium grandiflorum, a beautiful three-petaled white flower with six stamens.

5 Purple flower 042316This purple flower is unknown to me so far. I hope a kind expert adds its name in the comments![Lyn Loveless again is the kind commenter: “Phlox divaricata – Wild blue phlox.”]

 

Wooster’s Fossil of the Week: A thoroughly encrusted rugose coral from the Upper Ordovician of southeastern Indiana

April 22nd, 2016

1 Rugosan Exterior 123015It doesn’t look like much, this long lump of gray stone. With a close view you might pick up a hint of a bryozoan or two, but mostly we see rather shabby shades of grey. One of the coolest perks of being a geologist, though, is that you get to use a saw to cut rocks in half to see what’s inside. So that’s what I did with this specimen from the Whitewater Formation (Upper Ordovician) of southeastern Indiana at a site we’ve visited often.

2 Rugosan interior 123015In this cross-section we see first a long, cone-shaped fossil made of white calcite. It is the rugose coral Grewingkia canadensis, one of the most common fossils in the upper part of the Upper Ordovician. This coral in life would have stood upright like an ice cream cone, spreading the tentacles of its polyp to catch very small swimming prey (and maybe to do a bit of symbiotic photosynthesis). The polyp sat in the cup-like cavity on the expanded end of the cone. The coral evidently died on the Ordovician seafloor and toppled over to be encrusted on one side, presumably the one that faced upwards.

3 Coral Bryo Sed BryoThis is a closer view of the cross-section showing the encrustations on the rugose coral skeleton. The image is annotated below.

4 Coral Bryo Sed Bryo annotatedThe coral skeleton in the lower right was first encrusted by a trepostome bryozoan, which you can recognize by the tubes (zooecia) extending perpendicular from the substrate. This bryozoan is thickest on the upwards-facing surface of the coral, and it thins as it wraps around and then colonizes the cryptic space beneath (but not too far). This bryozoan is covered with a layer of sediment which appears to have rapidly cemented in place (a function of Calcite Sea geochemistry). The sediment then is encrusted by a another trepostome bryozoan with long zooecia and several layers.

5 Bryo Sed 123015In this closer view of the second bryozoan you can see that its base is irregular as it grew across the rough cemented sediment surface. In the middle of this view some of the bryozoan zooecia are occupied by dark spots known as brown bodies. These are likely the remains of bryozoan polypides (main parts of the individual zooids) that were sealed into their zooecia by some disturbance. In this case the whitish bit of sediment above the cluster may represent something that settled on the colony, stopping the growth of the zooecia below, and forcing those nearby to grow around it.

6 Borings 123015Moving down the coral skeleton away from its opening we come across borings drilled down through the coral skeleton (the white mass at the bottom of the image). The conical, large boring is filled with golden crystals of the mineral dolomite, which were formed long after burial. The shape of this boring is unusual. Typical borings in these corals have straight parallel sides, but this boring is cone-shaped. We’ll see if we can find more like it to get a better idea of its shape and distribution.

This week’s fossil, then, is a demonstration of the hidden wonders sometimes found in even the dullest of grey rocks!

 

Wooster’s Fossil of the Week: An atrypid brachiopod from the Devonian of Spain

April 15th, 2016

1 Atrypid dorsal Lr Couvinian M Dev El Pical Leon SpainOur featured fossil this week is another gift from brachiopod enthusiast Clive Champion of England. This fine specimen of Atrypa sp. was collected from the Middle Devonian (Lower Couvinian) exposed at El Pical, Leon, Spain. Atrypa is the emblematic genus of the atrypid brachiopods, which were common in the Devonian around the world. They were also prominent in the Late Ordovician of the Cincinnati region, as seen here and here. We are looking at the dorsal valve in the above view.

2 Atrypid spiraliaThis particular specimen is not notable for its special beauty (it is, after all, exfoliated and a bit misshapen), but for the view it provides of an internal feature: the spiral brachidium, sometimes called the spiralia. This was a ribbon of calcite that supported the lophophore, a tentacular apparatus used in filter-feeding. We see it here because the dorsal valve eroded away, exposing the inside of the shell. Our friends at The Falls of the Ohio have another specimen showing the spiral lophophore of an atrypid.

3 Atrypid ventralThis is a view of the flat ventral valve of our atrypid brachiopod. Inside during life the spiral lophophore would have looked like two springs perpendicular to the floor of this valve.

Thank you again, Clive, for the beautiful and inspiring brachiopods!

References:

Bose, R. 2013. A geometric morphometric approach in assessing paleontological problems in atrypid taxonomy, phylogeny, evolution and ecology, p. 1-9. In: Biodiversity and Evolutionary Ecology of Extinct Organisms. Springer, Berlin and Heidelberg.
Rudwick, M.J.S. 1960. The feeding mechanisms of spire-bearing fossil brachiopods. Geological Magazine 97: 369-383.

 

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