Archive for April, 2012

Wooster’s Fossil of the Week: the classic bioclaustration (Upper Ordovician of Ohio)

April 29th, 2012

We’re looking at two fossils above. One is the bryozoan Peronopora, the major skeletal structure. The second is the odd series of scalloped holes in its surface. These are a trace fossil called Catellocaula vallata Palmer and Wilson 1988. They at first appear to be borings cut into the bryozoan colony. Instead they are holes formed by the intergrowth of a soft-bodied parasite with the living bryozoan colony. This type of trace fossil is called a bioclaustration. We gave it the Latin name for “little chain of walled pits”.

My good friend Tim Palmer and I found this specimen and many others in 1987 as we explored the Upper Ordovician Kope Formation in the Cincinnati region. We were collecting bioeroded substrates like hardgrounds and shells, and these features were clearly different from the usual borings. They do not actually cut the bryozoan skeleton, for one thing. For another it is apparent that the bryozoan growth was deflected around whatever sat in those spaces. Tim and I called this kind of interaction “bioclaustration”, meaning “biologically walled -up”.
Catellocaula vallata on the Upper Ordovician bryozoan Amplexopora. Note that the scalloped holes have more lobes than those seen in the lead image. This may mean it was a different species of infesting soft-bodied organism.

The infesting parasite on the bryozoan colony was itself colonial, consisting of small clusters connected by extended stolons. The bryozoan grew around the parasite, roofing over the stolons and making walls on the margins of the clusters. We think the parasite was a soft-bodied ascidian tunicate like the modern Botryllus. If true, it is the earliest fossil tunicate known.

This closer view of C. vallata shows the scalloped margins of the pits and the horizontal connections between them.

Another specimen of C. vallata. This view shows the flat floors of the bioclaustration features.

Acetate peels cut longitudinally through the bryozoan and bioclaustrations. On the left you can see that the bryozoan zooecia (long tubes) were deflected sideways as they grew. On the right is a tunnel connecting two pits, with bryozoan zooids forming the roof. (From Palmer and Wilson, 1988.)

References:

Bromley, R.G., Beuck, L. and Taddei Ruggiero, E. 2008. Endolithic sponge versus terebratulid brachiopod, Pleistocene, Italy: accidental symbiosis, bioclaustration and deformity. Current Developments in Bioerosion, Erlangen Earth Conference Series, 2008, III, 361-368.

Palmer, T.J. and Wilson, M.A. 1988. Parasitism of Ordovician bryozoans and the origin of pseudoborings. Palaeontology 31: 939-949.

Tapanila, L. 2006. Macroborings and bioclaustrations in a Late Devonian reef above the Alamo Impact Breccia, Nevada, USA. Ichnos 13: 129-134.

Taylor, P.D. and Voigt, E. 2006. Symbiont bioclaustrations in Cretaceous cyclostome bryozoans. Courier Forschungsinstitut Senckenberg 257: 131-136.

A very damp field trip

April 28th, 2012

FAIRBORN, OHIO–I actually used to brag about the great weather on my class field trips. The hubris! Today Shelley Judge and I took our combined Sedimentology & Stratigraphy and Structural Geology classes to Oakes Park Quarry near Dayton for a field trip. (Location = N39.81401°, W083.98374°.) We planned to describe and measure the exposure there of the Brassfield Formation, and then assess the joint fabric and the direction of glacial grooves on its top surface. I took three students there last week to test the concept. Since this is the last weekend of the semester, there was no do-over, so we went rain or shine.

It was 38°F and breezy when we arrived. That’s when I took my first and last picture, shown above. (It is of Tricia Hall and Scott Kugel in the middle of their stratigraphic task.) The rain came slowly at first. Not too bad. Then we heard the thunder and were quickly overwhelmed by a serious downpour. Near-freezing temperatures and a thunderstorm? That’s spring in Ohio. I haven’t been so cold and wet since I was in this place. This is why I very much prefer my field areas to be very warm and very dry.

The students were great sports, though, and we collected just enough data so that we could retreat to the bus with some geological honor intact.

The summer can’t come fast enough back here for the Wooster geologists!

Wooster Geologists at the 2012 Senior Research Symposium

April 27th, 2012

WOOSTER, OHIO–Six Wooster geology seniors presented their research to the campus and public this morning in Kauke Hall on the College of Wooster campus. They were among the first posters in the annual Senior Research Symposium in which Independent Study projects are highlighted and celebrated. They did very well — their geology faculty advisors are proud indeed. Here they are with their presentations:

Sarah Appleton ’12: Dating of the Mid-Holocene History and Glacial Stratigraphy of the Wachusett Inlet, Glacier Bay National Park and Preserve, Southeast Alaska. (Links to Sarah’s work on the Wooster Geologist’s blog.)

Lindsey Bowman ’12: Geochemical and Field Relationships of Pillow and Dike Units in a Subglacial Pillow Unit, Undirhlíðar Quarry, Southwest Iceland. (Links to Lindsey’s work on the Wooster Geologists blog.)

Andrew Collins ’12: A Comparison and Analog-Based Analysis of Sinuous Channels on Rift Aprons of Ascraeus Mons and Pavonis Mons Volcanoes, Mars. (Links to Andrew’s work on the Wooster Geologists blog.)

Nick Fedorchuk ’12: Stratigraphy and Paleoecology of the Wenlock/Ludlow Boundary on Saaremaa Island, Estonia. (Links to Nick’s work on the Wooster Geologists blog.)

Rachel Matt ’12: Paleoecology of the Hilliste Formation (Lower Silurian, Llandovery, Rhuddanian) on Hiiumaa Island, Estonia: An Example of a Shallow Marine Recovery Fauna. (Links to Rachel’s work on the Wooster Geologists blog.)

Katharine Schleich ’12: A Geochemical and Petrographic Analysis of the Hrafnfjordur Central Volcano, Westfjords, Iceland. (Links to Katharine’s work on the Wooster Geologist blog.)

Well done, Wooster Geologists!

 

Wooster’s Fossil of the Week: a nestling bivalve (Pleistocene of The Bahamas)

April 22nd, 2012

This weathered and encrusted shell was pulled from a round hole bored in a Pleistocene reef (about 125,000 years old) exposed on San Salvador Island, The Bahamas. It is Coralliophaga coralliophaga (Gmelin 1791), a derived venerid bivalve (a type of heterodont, meaning that it has cardinal and lateral articulating teeth inside its valves.) I collected it back in 1991 while studying an inter-reef unconformity that recorded a drop and rise of sea level (Wilson et al., 1998; Thompson et al., 2011).

Coralliophaga means “coral eater”, which is a bit of a bum rap for this clam. It is found inside borings in coral, true enough, but those holes were drilled by some other types of clams. C. coralliophaga only occupies the holes after the original dweller is dead and gone (Morton, 1980). We call this kind of behavior “nestling“, which seems a polite way of saying “squatting”. These bivalves grew to adulthood in these cavities protected from most predators as they filtered the seawater for food.
The trace fossil Gastrochaenolites torpedo (the elongate borings) with a nestling (and broken) C. coralliophaga in the lower right corner.

The posterior ends of these shells are encrusted by a variety of calcareous algae and other organisms during life, so they look a bit rough on their outsides. Often the encrustations are so thick that the shells are difficult to extract from the holes, so getting a nice complete shell like the one at the top of this entry is rare.
C. coralliophaga was named by Johann Friedrich Gmelin (1748–1804) in 1791. Gmelin was an accomplished naturalist from Tübingen, Germany. He received an MD degree in 1769, with his father (Philipp Gmelin) as his advisor. He taught at Tübingen and the University of Göttingen, writing many textbooks in fields from chemistry through botany. He published the 13th edition of Systema Naturae by Carolus Linnaeus, inserting his new taxa in the text, including our new friend Coralliophaga coralliophaga.

References:

Gmelin, J.F. 1791, in Linnaeus, C. Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis. 13th Edition, Lyon : J.B. Delamolliere Tom.

Morton, B. 1980. Some aspects of the biology and functional morphology of Coralliophaga (Coralliophaga) coralliophaga (Gmelin, 1791) (Bivalvia: Arcticacea): a coral-associated nestler in Hong Kong. pp. 311-330, in: Morton, B., The Malacofauna of Hong Kong and southern China. Proceedings of the First International Workshop on the Malacofauna of Hong Kong and Southern China, Hong Kong, 1977. Hong Kong: Hong Kong University Press.

Thompson, W.G., Curran, H.A., Wilson, M.A. and White, B. 2011. Sea-level oscillations during the Last Interglacial highstand recorded by Bahamas corals. Nature Geoscience 4: 684–687.

Wilson, M.A., Curran, H.A. and White, B. 1998. Paleontological evidence of a brief global sea-level event during the last interglacial. Lethaia 31: 241-250.

Wet and Cold Wooster Geologists in the Silurian of Central Ohio

April 21st, 2012

DAYTON, OHIO–It was 37°F and raining this morning as three stalwart Wooster Geology students and I worked in a muddy quarry near Fairborn, Ohio (N 39.81472°, W 83.99471°). Our task was to scout out a beautiful exposure of the Brassfield Formation (Early Silurian, Llandovery) for a future field trip by the Sedimentology & Stratigraphy class. Until today this week was sunny and warm in Ohio. Nevertheless, our students persevered and efficiently measured and described the exposed units, and then they searched for glacial grooves and truncated corals on the top surface.

Abby, Steph and Lizzie during a relatively dry moment. The striped stick, by the way, is a Jacob’s Staff divided into tenths of meters. We use these large and simple rulers to measure the thickness of rock units. Our technician Matt Curren made us nice set of these this semester. Previous Wooster students may remember the long dowels we had in the past that Stephanie Jarvis discovered one day were not very precise! Why do we call them “Jacob’s Staffs”? Read Genesis 30:25-43. (This must be the first biblical reference in this blog!)

Dolomite at the base of the Brassfield with a pervasive fabric of burrows. These trace fossils were probably produced by shrimp-like arthropods tunneling in the seafloor sediments.

A well-sorted encrinite (limestone made almost entirely of crinoid skeletal fragments) from the lower third of the Brassfield Formation. These are mostly stem and arm pieces. The articulated portion on the left is a small stem.

A poorly-sorted encrinite. Here you can see a much greater range of bioclast size than in the previous image. There are also some brachiopod shell fragments mixed in.

The Brassfield Formation is a critical one in stratigraphy because most of the other Silurian carbonates in northeastern North America have been altered by dolomitization, which destroys the original fabric and texture of the rock. Fossils become mere ghosts in dolomitized limestone, but here they are superbly preserved.

It may have been a damp and chilly day, but how bad could it have been if we had limestones and fossils in it?

Expanding Horizons in Geology

April 16th, 2012

WOOSTER, OH – The Wooster Geologists are pleased to be part of the Expanding Your Horizons Program, a science workshop aimed at encouraging young women to consider science as a career. This year’s topics ranged from sunscreen to marshmallow-spaghetti towers. Our workshop focused on minerals in common household products. We’ve ran this workshop once or twice before, but now that the X-ray lab is fully established, we’ve (mostly) worked out the kinks.

The girls began the workshop by guessing which minerals were in which products based on physical properties of the minerals.

We tested their hypothesis for toothpaste by running a sample in the XRD, which provides us with a "fingerprint" of the minerals in the sample.

This particular toothpaste contained a mixture of two minerals, so the girls needed to do some detective work to figure out which parts of the fingerprint belonged to which mineral.

The girls were expert geologists, correctly matching each of the minerals to their products. A special thanks to Wooster Geology Major Anna Mudd for guiding the girls through their experiment!

 

Wooster’s Fossil of the Week: A scale tree root in its own soil (Upper Carboniferous of Ohio)

April 15th, 2012

Last week a local man, Larry Stauffer, brought in the above fossil for identification and then kindly donated it to the department. It is part of the root system of Lepidodendron, the “scale tree” of the Carboniferous Period. What is especially cool about it is that the rootlets, thin ribbon-like perpendicular extensions, are still attached. Usually they were lost quickly when the root was dislodged from its bed.

The well-preserved rootlets show that this bit of root is still in its original soil. Such a fossil soil is called a paleosol. These features are important in the rock record because they show ancient climate conditions, weathering profiles and sedimentation rates. Carboniferous paleosols like this are called seat earth.

The roots of Lepidodendron were given a separate generic name in 1822 by the French naturalist Alexandre Brongniart (1770-1847). He called them Stigmaria because of the regularly-spaced holes called stigmata. (You may know “stigmata” from an entirely different context!) The name was superseded by Lepidodendron once it was figured out how the roots, trunk, and leaves were connected.

Diagram of “Stigmaria ficoides“  from “Elements of Geology: The Student’s Series” by Charles Lyell (1871).

Brongniart is best known to me as one of the first biostratigraphers. He worked out the first divisions of the Tertiary Period (now known as the Paleogene and Neogene Periods) using fossils to mark time intervals. He also was the first to systematically study the trilobites at the other end of the geologic time scale. Brongniart did original geological mapping with the famous Georges Cuvier in the Paris region as well. He was a professor at the École de Mines and director of the Sèvres porcelain factories. I think he looks rather friendly in a Frenchy way.

References:

Brongniart, A. 1822. Sur la classification et la distribution des végétaux fossiles en général, et sur ceux des terrains de sédiment supérieur en particulier. Soc. Philom., Bull., pp. 25-28 and Mémoires Du Muséum d’Histoire Naturelle 8: 203–240, 297–348.

Frankenberg, J.M. and Eggert, D.A. 1969. Petrified Stigmaria from North America: Part I. Stigmaria ficoides, the underground portions of Lepidodendraceae. Palaeontographica 128B: 1–47.

Jennings, J.R. 1977. Stigmarian petrifications from the Pennsylvanian of Colorado. American Journal of Botany 64: 974-980.

Rothwell, G.W. 1984. The apex of Stigmaria (Lycopsida), rooting organ of Lepidodendrales. American Journal of Botany 71: 1031-1034.

Sand and Gravel in the Holmesville Moraine

April 13th, 2012

The College of Wooster Geomorphology class set out to explore the Holmesville Moraine, a 20 minute drive south of Wooster straight down the Killbuck River Valley. It was a beautiful day, except for the rain. The first stop was Holmesville Sand and Gravel, a company which mines and sorts the deposit and sells it for various building and homeowner applications. We ended up classifying this as a Kame Moraine as most of the sediment is sand and gravel intermixed with diamict all piled up into a great cross valley ridge. This is likely the dam for Glacial Lake Killbuck, which was impounded to the north.

The Separator - This machine and associated conveyors sorts the gravel from the sand from the silt.

Sorted piles – note the varying angles of repose.

 

 

 

 

 

 

 

 

 

 

 

 

 

The dredge sucks sand from 70 feet down in this lake. It is then piped to the Separator.

 

Fine-grained sand and silt is returned to the lake – note the delta. A wave-dominated delta that is revealed with a modest drop in lake level.

Continue reading this post to see why the group is dumbfounded.

Ice-contact stratified drift – sediments range from diamicts to stratified sands and gravels. Many of the gravels are cemented. Note that the lower left is a bedrock contact. This is the guts of the kame moraine.

Cemented sand and gravel – note the evenly-space joints where the rivelets have excavated the materials – joints from unloading?

Cemented and partially stratified diamict – this unit is a major challenge to remove in mining.

Raindrop imprints on mudcracks.

Ditch draining the floor of former Glacial Lake Craigton – note the peaty sediments and the tiles. Note the meandering thalweg within the ditch.

A Drool-Worthy College Museum

April 11th, 2012

AMHERST, MA – Last weekend, some Wooster Geologists attended the Keck Symposium at Amherst College and were awed by their geology museum. The Beneski Museum of Natural History  is housed in a modern building and covers three floors, displaying over 1,700 specimens. The museum hosts the Hitchcock Ichnology collection, the world’s largest collection of dinosaur footprints. Other highlights include the wall of mammals, an impressive mineral collection, and exquisite table tops of polished stone. Here are a few photos that might just make your jaw drop.

A large mastodon and other mammals greet visitors as they enter the museum.

The Hitchcock Ichnology Collection is the largest collection of dinosaur footprints in the world.

Casts of dinosaur footprints featured on the Hitchcock Collection webpage.

Was the dinosaur running or walking to make these tracks?

A large mold.

The cast that fits into the mold above.

Fossilized mudcracks, viewed from below.

Fossilized raindrops.

The petrified trunk of an ancient tree.

Want to keep a geologist busy for hours? Give her a countertop that looks like this.

 

 

Wooster’s Fossils of the Week: A calcareous sponge with a crinoid holdfast (Matmor Formation, Middle Jurassic, Israel)

April 8th, 2012

The Class Calcarea of the Phylum Porifera is a group of sponges characterized by spicular skeletons made of calcium carbonate (calcite in this case). The spicules (small elements of the skeleton) are often fused together, causing the sponges to look a bit like corals or bryozoans. They are among the most common fossils in the Matmor Formation (Middle Jurassic, Callovian) of southern Israel. Melissa Torma and I collected this particular fossil on our expedition last month. It is another indication that the Matmor Formation was deposited in very shallow waters.
This is the underside of the Matmor calcareous sponge. (I wish we had a name for it, but the taxonomy is in considerable flux right now.) You can see the way it grew radially around an encrusting center. In the lower right a circular oyster attachment is visible.
A close view of the top surface of the calcareous sponge showing radiating canals called astrorhizae. They were used to channel water currents for the sponge’s filter-feeding system.
This crinoid holdfast (the base of an attaching stem) locked onto the calcareous sponge after its death. We can tell this because it is bound to the spicular skeleton itself, which was only exposed after the sponge’s soft tissues rotted away. It is not possible to identify the crinoid, but it is likely in the genus Apiocrinites.
The Class Calcarea was named by James Scott Bowerbank in 1864. Bowerbank (1797-1877) was an English naturalist born in London. He helped run a distillery with his brother, making enough money to support his diverse interests in natural history. He collected many fossils in his life, specializing in the London Clay (Eocene). His various publications gained him membership in the Royal Society in 1842. His greatest work was probably a four-volume set titled “A Monograph of the British Spongidae”. (You can read at least part of this work online.) He was well known as a strong supporter of young scientists, opening his home and collections (and use of his valuable microscopes) to all those seriously interested in natural history. I like to think he would have been happy as a liberal arts geology professor!

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