Archive for February, 2012

Accretionary Wedge #43: Fun with Chemographic Projections

February 29th, 2012

This month’s Accretionary Wedge calls for posts on our favorite geological illustrations. Some of my personal favorites are drawn by Dr. Kurt Hollocher from Union College. His collection of hand-drawn thin sections is enough to make any petrologist drool.

One of Dr. Hollocher’s most whimsical illustrations involves the AFM chemographic projection. Chemographic projections are often used in metamorphic petrology to plot complex compositions on two-dimensional triangular diagrams. A popular chemographic projection for metapelites is the AFM diagram, which represents Al2O3, FeO, and MgO at its corners. In his series of AFM diagrams, Dr. Hollocher has a little fun with the retrograde garnet-out reaction.

Retrograde chloritoid-in reaction. Courtesy of Dr. Kurt Hollocher.

Poor garnet. Courtesy of Dr. Kurt Hollocher.

Garnet is doomed! Courtesy of Dr. Kurt Hollocher.

Goodbye garnet. Courtesy of Dr. Kurt Hollocher.

The progressive garnet-out reaction. Courtesy of Dr. Kurt Hollocher.

Almost gone. Courtesy Dr. Kurt Hollocher.

Hello chlorite pesudomorph after garnet! Courtesy of Dr. Kurt Hollocher.

Special thanks to Dr. Kurt Hollocher for the fantastic illustrations and the permission to use them in our Accretionary Wedge Post.

Wooster’s Fossil of the Week: A holey brachiopod (Lower Cretaceous of southeastern Spain)

February 26th, 2012

This striking and unusual brachiopod is Pygites diphyoides (d’Orbigny, 1847) from Hauterivian (Lower Cretaceous) of Cehegin, Murcia, Spain. Wooster acquired it through a recent generous exchange of brachiopods with Mr. Clive Champion in England. I had heard about this brachiopod genus with a hole through its shell, but never before actually seen one. Thank you very much, Clive.

Pygites diphyoides is a terebratulid brachiopod, an order that is still in existence today. It is commonly called a “keyhole brachiopod” because of the perforation running vertically through the shell. It attached to the substrate with a pedicle (a stem-like device protruding through the pointy end of the shell). Pygites and its relatives appear to have been adapted deep sea, poorly oxygenated conditions, although they are found in shallower facies as well (Dieni and Middlemiss, 1981; Kazmer, 1993; Michalik, 1996).
In this reconstructed cross-section of Pygites (from Michalik, 1996, fig. 4) we can see how the central perforation may have helped with the flow of nutrient-bearing currents through the shell. (Although I must admit to being a bit baffled by the arrows!)
Pygites diphyoides was orginally described as “Terebratula diphyoides” in 1847 by the famous French naturalist Alcide Charles Victor Marie Dessalines d’Orbigny (1802-1857). He was a prolific scientist in many fields, including paleontology, general geology, zoology, archaeology and anthropology. D’Orbigny was a native Frenchman who grew up on the Atlantic coast of his country. He was especially fascinated with marine organisms, even giving the name (in 1826) to a group of protists we now know as “foraminiferans“. He was a proponent of the ideas of his countryman and esteemed zoologist Georges Cuvier during what were exciting times in the development of zoology and paleontology. He was an astonishingly productive scientist, with dozens of reports, papers and books to his credit, and he accumulated a spectacular collection of fossils and zoological specimens. D’Orbigny combined geology and paleontology in very useful ways, becoming one of the earliest biostratigraphers. As a Cuvier disciple, though, he believed the rock record showed a series of successive catastrophes and new creations, so he rejected the developing ideas of evolution during his lifetime (Taylor, 2002).

In 1853 d’Orbigny became professor of paleontology at the Paris Muséum National d’Histoire Naturelle, a new chair created for him. He died at the shockingly young age (for me!) of 54 years.

My friend Paul Taylor at the Natural History Museum in London knows the work of Alcide d’Orbigny very well, and is an expert in his voluminous collections of bryozoans, which you can read about at the link. You will see that the legacy of d’Orbigny is a bit mixed when it comes to his taxonomic contributions, so Paul has his challenges when it comes to sorting out the many names and descriptions this active scientist produced.

References:

Dieni, I. and Middlemiss, F.A. 1981. Pygopid brachiopods from the Venetian Alps. Bollettino della Societá Paleontologica Italiana 20: 19–48.

Kazmer M. 1993. Pygopid brachiopods and Tethyan margins. In: Palfy, J., Voros, A. (eds.), Mesozoic Brachiopods of Alpine Europe. Hungarian Geological Society, Budapest, pp. 59-68.

Michalik, J. 1996. Functional morphology – paleoecology of pygopid brachiopods from the western Carpathian Mesozoic. In: Copper, P. (ed.), Brachiopods: proceedings of the third International Brachiopod Congress, Sudbury, Ontario, Canada, 2-5 September, 1995. CRC Press.

d’Orbigny, A. 1847. Pal. franc., terr. crét., 4, p. 87, pl. 509. Barreme, Lieous, Berrias, Mons, près d’Alais.

Taylor, P.D. 2002. Alcide d’Orbigny (1802-1857). The Linnean 18: 7-12.

Wooster Geologists Visit the Miller Oil and Gas Museum in Shreve, Ohio

February 21st, 2012

Geology 350 - The Oil and Gas of Geology spending a beautiful day in Shreve.

Drs. Judge and Wiles are teaching a half credit course in The Geology of Oil and Gas. After weeks of well log interpretation, rock core description and interpretive contour mapping exercises the class caught a break and traveled to the Miller Oil and Gas Museum on a beautiful February day in Shreve Ohio. We are grateful to the Raymond’s for showing us around the museum and explaining the use of the some of the equipment.

 

Picking out a plug for an abandoned well.

 

Fishing tools for when there is a problem or a lost drill string downhole.

A proponent of the health benefits of oil.

A class cube - the small class size at Wooster is measured in a cube cell.

One of the old rigs of the oilfields.

A question that commonly comes up is "what would an oilfield geologist do with a cannon?" (see below)

A creative solution to the problem of managing a flaming oil well.

Looking over a field rig.

Destined for law school this geologist models next to a drill string tamper.

 

 

Wooster’s Fossils of the Week: star sand (Recent of southern Japan)

February 19th, 2012

Yes, that “Recent” in the title was a clue that these are not actually fossils, but the little beauties fit the spirit of our series. This is sand from an unknown island beach in southern Japan. The spotted star-shaped grains are the foraminiferan Baculogypsina sphaerulata (Parker & Jones, 1860). They occur by the billions in tropical and sub-tropical parts of the Pacific Ocean.
Foraminifera are single-celled organisms that often build shells (tests) of calcite and other materials. They have a long fossil record, and we know their evolutionary history in great detail. Foraminifera are thus excellent index fossils for correlating rock units and estimating geological time relationships.
Baculogypsina sphaerulata collected on the famous HMS Challenger expedition of 1873-1876. Image from Brady (1884).

Baculogypsina sphaerulata is an especially interesting foraminiferan. It has a radial canal system that gives it a characteristic star shape. Like many other larger foraminiferans, they have other organisms living inside their tissues called endosymbionts. Here the endosymbionts are pennate (feather-like) diatoms (which was news to me). Diatoms are photosynthetic so they require sunlight to make their carbohydrates. They cluster next to the most transparent parts of the Baculogypsina test interiors, using them like windows to catch some rays. The diatoms release carbohydrate metabolites and oxygen which are used by the host foraminiferan, completing the mutually-beneficial symbiotic relationship.

References:

Brady, H.B. 1884. Report on the Foraminifera dredged by H.M.S. Challenger during the years 1873-1876. Report of the scientific results of the voyage of H.M.S. Challenger, 1873-1876, Zoology 9: 1-814.

Hyams-Kaphzan, O. and Lee, J.J. 2008. Cytological examination and location of symbionts in “living sands” — Baculogypsina. Journal of Foraminiferal Research 38: 298-304.

Lee, J.J., Faber, W.W., Nathanson, B., Roettger, R., Nishihira, M. and Krueger, R. 1993. Endosymbiotic diatoms from larger Foraminifera collected in Pacific habitats. Symbiosis 14: 265-281.

Lee, J.J., Morales, J., Symons, A. and Hallock, P. 1995. Diatom symbionts in larger foraminifera from Caribbean hosts. Marine Micropaleontology 26: 99-105.

Röttger, R. and Krüger, R. 1990. Observations on the biology of Calcarinidae (Foraminiferida). Marine Biology 106: 419-425.

Geology and art meet with a ceramic creation from the Cretaceous extinctions

February 16th, 2012

In August 2010 I had a fantastic geologic field trip to the tunnels of Geulhemmmerberg, The Netherlands, to see an unusual exposure of the Cretaceous-Paleogene boundary. There I collected a fist-sized sample of the famous boundary clay, which is found in a variety of thicknesses around the world. I knew just what to do with this sticky handful: give it to my artist friend Walt Zurko at The College of Wooster. He generously made the gorgeous cup-like object above and presented it to me this week.

Walt used every scrap of the clay, even recycling the shavings back into the exterior. There were tiny rock fragments in the original clay sample. They expanded differentially during the heating process and one made a small crack at the lip. I like it — it gives the piece character, like the crack in the Liberty Bell. Walt used several techniques to produce an extraordinary patina on the outside, much of which is not adequately conveyed in my amateur image.

Now we have in the geology department at Wooster a beautiful work of art made from the most famous clay in geological history. Aren’t the liberal arts wonderful?

Inside the tunnels at Geulhemmmerberg, The Netherlands, in August 2010. The rock forming the ceiling is Paleogene and most of the walls are made of Cretaceous limestone. The Cretaceous-Paleogene boundary is visible about a third of a meter down from the top of the wall in the background.

The complicated Cretaceous-Paleogene boundary at Geulhemmmerberg, The Netherlands. This gray clay is one of the thickest boundary clays in the world. I collected a chunk from this section for Walt’s artistic creation.

Wooster’s Fossil of the Week: An asteroid trace fossil from the Devonian of northeastern Ohio

February 12th, 2012

It is pretty obvious what made this excellent trace fossil: an asteroid echinoderm. (The term “asteroid” sounds odd here, but it is the technical term for a typical sea star.) The above is Asteriacites stelliformis Osgood, 1970, from the Chagrin Shale (Upper Devonian) of northeastern Ohio.

We can tell that it was made by a sea star burrowing straight down into the sediment because it has faint chevron-shaped marks in the rays made by tube feet as they moved sediment aside. The mounds of excavated sediment can be seen between the rays at their bases. This tells us that we are not looking at an external mold of a dead sea star, but instead its living activity. This is what a trace fossil is all about.

A living asteroid from the shallow sea off Long Island, The Bahamas. (The hand belongs to my son, Ted Wilson.)

The ichnogenus Asteriacites was named by von Schlotheim in 1820. We profiled him earlier with the genus Cornulites. The author of Asteriacites stelliformis was Richard G. Osgood, Jr., my undergraduate advisor and predecessor paleontologist at The College of Wooster.
Richard Osgood, Jr., was born in Evanston, Illinois, in 1936. He went to Princeton for his undergraduate degree (I still remember his huge Princeton ring) and received his Ph.D. from the University of Cincinnati. He worked for Shell Oil Company in Houston just prior to joining the Wooster faculty in 1967. He was one of the pioneers of modern ichnology (the study of trace fossils), naming numerous new ichnotaxa and providing ingenious interpretations of them. At least one trace fossil was named after him: Rusophycus osgoodii Christopher, Stanley and Pickerill, 1998. Dr. Osgood died in 1981 in Wooster. He was an inspiration to me and many other Wooster geology students during his productive career, which was all too short.

References:

Osgood, R.G., Jr. 1970. Trace fossils of the Cincinnati area. Palaeontographica Americana 6: 281-444.

Schlotheim, E.F. von. 1820. Die Petrfactendunde auf ihrem jetzigen Standpunkte durch die Beshreibung seiner Sammlung versteinerter und fossiler Überreste des Thier- und Pflanzernreichs der Vorwelt erläutert 1-457.

Stanley, D.C.A. and Pickerill, R.K. 1998. Systematic ichnology of the Late Ordovician Georgian Bay Formation of southern Ontario, eastern Canada. Royal Ontario Museum Life Sciences Contribution 162, 56 pp., 13 pl. Toronto.

Wooster’s Fossil of the Week: A mysterious sponge (Late Ordovician of Ohio)

February 5th, 2012

I’ve been collecting and studying fossils from the Upper Ordovician of the Cincinnati region for three decades now, but I’ve never seen another specimen like the one pictured above. An amateur collector, Howard Freeland, generously donated this rock to Wooster late last year. He found it in Cincinnatian limestones cropping out in Brown County, Ohio.

At first Howard understandably thought he had found fish bones, which would be extraordinary for this age of rock and place of deposition. He took the slab to the Smithsonian Institution for identification by a vertebrate paleontologist. Not bones, was the answer, but they didn’t know how else to classify these finger-like fossils. When Howard showed them to me I suggested they were fossil sponges, and so here we are. I could be wrong so I hope the web community has some other ideas.

I believe these are sponge pieces because they were originally hollow (now they are filled with sediment), fibrous in structure, and had small holes irregularly preserved on their surfaces. They look in texture like the hexactinellid sponge Brachiospongia, but they do not have their distinctive thick extensions and radiating shape.

Small, irregular holes on fossil surface. They could be sponge incurrent pores. I would expect them to be more regular, though.

My search of the Ordovician sponge literature (what there is of it) has not turned up anything similar. I’ve gone to the usual websites for the Cincinnatian (like Steve Holland’s excellent Cincinnatian fossil catalog and the Dry Dredger’s webpages), but no luck.

Sometime during the existence of this webpage someone will come across these images and post their solution in the comments. I look forward to learning from them!

Reference:

Carrera, M.G. and Rigby, J.K. 1999. Biogeography of Ordovician sponges. Journal of Paleontology 73: 26-37.