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?

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.

Wooster’s Fossil of the Week: A spiriferinid brachiopod (Logan Formation, Lower Carboniferous, Ohio)

April 1st, 2012

This brachiopod is one of the most common in the Logan Formation of Wooster, Ohio, so our students know it well from outcrops in Spangler Park and the occasional excavations in town. Four specimens of Syringothyris Winchell 1863 are visible in the slab above. The critter in the upper left is an earlier Fossil of the Week: the bivalve Aviculopecten subcardiformis. This suite of fossils is about 345 million years old (Osagean Series of the Lower Carboniferous).
We can’t identify the species of these Logan Formation brachiopods because the original shells dissolved away long ago. We are left with the sediment that filled the insides of the shells, producing what paleontologists call internal molds. Syringothyris belongs to the Order Spiriferinida, a group of elongate brachiopods that are punctate, meaning there are tiny holes penetrating their shells. Unfortunately this is one feature I can’t show you with internal molds!
Alexander Winchell (1824-1891) named and first described the genus Syringothyris. He was a geology professor at the University of Michigan for decades, specializing in Lower Carboniferous stratigraphy and paleontology. He was also the state geologist of Michigan. Winchell was one of the early American Darwinists, working hard to reconcile religion and science in the United States (with decidedly mixed results!).

References:

Bork, K.B. and Malcuit, R.J. 1979. Paleoenvironments of the Cuyahoga and Logan Formations (Mississippian) of central Ohio. Geological Society of America Bulletin 90: 89–113.

Winchell, A. 1863. Descriptions of FOSSILS from the Yellow Sandstones lying beneath the “Burlington Limestone,” at Burlington, Iowa. Academy of Natural Sciences of Philadelphia, Proceedings, Ser. 2, vol. 7: 2-25.

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.

Wooster’s Fossils of the Week: Bivalve escape trace fossils (Devonian and Cretaceous)

January 29th, 2012

It is time again to dip into the wonderful world of trace fossils. These are tracks, trails, burrows and other evidence of organism behavior. The specimen above is an example. It is Lockeia James, 1879, from the Dakota Formation (Upper Cretaceous). These are traces attributed to infaunal (living within the sediment) bivalves trying to escape deeper burial by storm-deposited sediment. If you look closely, you can see thin horizontal lines made by the clams as they pushed upwards. These structures belong to a behavioral category called Fugichnia (from the Latin fug for “flee”). They are excellent evidence for … you guessed it … ancient storms.
The specimens above are also Lockeia, but from much older rocks (the Chagrin Shale, Upper Devonian of northeastern Ohio). Both slabs show the fossil traces preserved in reverse as sediment that filled the holes rather than the holes themselves. These are the bottoms of the sedimentary beds. We call this preservation, in our most excellent paleontological terminology, convex hyporelief. (Convex for sticking out; hyporelief for being on the underside of the bed.)

The traces we know as Lockeia are sometimes incorrectly referred to as Pelecypodichnus, but Lockeia has ichnotaxonomic priority (it was the earliest name). Maples and West (1989) sort that out for us.
Uriah Pierson James (1811-1889) named Lockeia. He was one of the great amateur Cincinnatian fossil collectors and chroniclers. In 1845, he guided the premier geologist of the time, Charles Lyell, through the Cincinnati hills examining the spectacular Ordovician fossils there. He was the father of Joseph Francis James (1857-1897), one of the early systematic ichnologists.

References:

James, U.P. 1879. The Paleontologist, No. 3. Privately published, Cincinnati, Ohio. p. 17-24.

Maples, C.G. and Ronald R. West, R.R. 1989. Lockeia, not Pelecypodichnus. Journal of Paleontology 63: 694-696.

Radley, J.D., Barker, M.J. and Munt, M.C. 1998. Bivalve trace fossils (Lockeia) from the Barnes High Sandstone (Wealden Group, Lower Cretaceous) of the Wessex Sub-basin, southern England. Cretaceous Research 19: 505-509.

Wooster’s Fossil of the Week: A scale tree (Late Carboniferous of Ohio)

January 8th, 2012

We haven’t had a plant fossil in this blog for awhile. Lepidodendron Sternberg 1820, pictured above, is one of the most common fossils brought to me in Wooster by amateur collectors. It is abundant in the Upper Carboniferous (Pennsylvanian) sandstones, shales and coals in this area. People sometimes call them “fossil snakes” because they are cylindrical and appear to have scales. Appropriately, the extinct plants they represent are called “scale trees” (the literal meaning of the genus name). The fossil above is an external mold of the trunk of this tree-like organism.
A plant as large and complex as Lepidodendron has many distinctive components that are often found separate from each other in the fossil record. These parts were given their own scientific names and only relatively recently were reunited into the genus Lepidodendron. The specimen above, for example, is traditionally known as Stigmaria and represents the roots of Lepidodendron.

From Book 15 of the 4th edition of Meyers Konversationslexikon (1885-90; figure 10). Lepidodendron is the tall tree on the left.

Diagrams of the trunk leaf scars (from Lesquereux, 1879).

Lepidodendron was up to 30 meters high in Carboniferous forests. It was tree-like, branching at the top and with a trunk covered with leaf scars. They are often called “club mosses” but are really related to modern quillworts (Isoëtes). They reproduced by spores, probably only once before death.
Lepidodendron was named and described by Kaspar Maria von Sternberg (1761-1838), a Czech naturalist who virtually founded the field of paleobotany. He was a philosophy student at the University of Prague when he began to collect fossils, minerals and plants, most of which eventually formed the nucleus of the National Museum in Prague. Oddly enough, he was also a theologian and received ordination in the Catholic church. He gave up his churchly duties early, though, and worked as a full-time scientist at various institutions in Central Europe. His description of Lepidodendron came from his deep studies of the fossils associated with coal mines in Bohemia.

References:

Lesquereux, L. 1879. Atlas to the coal flora of Pennsylvania and of the Carboniferous Formation throughout the United States. Second Geological Survey of Pennsylvania, Report of Progress.

Sternberg, K.M., von. 1820-1838. Versuch einer geognostisch-botanischen Darstellung der Flora der Vorwelt.

A Tale of Two Museums: Part 1 — The Cleveland Museum of Natural History

December 6th, 2011

Last week I had the marvelous opportunity to visit two very different museums with Wooster Geologists. This is the first of two posts with short vignettes of the memorable sights and sounds.

The first museum was the Cleveland Museum of Natural History. Greg Wiles and his Climate Change class invited me to accompany them to see the visiting climate change exhibit. It was an excellent display of the latest ideas about changing climates, including accurate accounts of the evidence, controversies and possible solutions to the problem of anthropogenic global warming and its associated troubles. It was a pleasure to see this presentation with Greg because of his deep and very current knowledge of the science and politics.

Since the above links give plenty of information about the museum and climate change exhibit, I’ll just highlight two features in front of the museum I found very interesting:

The large sundial above represents the history of life by geological periods. Note the beautiful ammonite fossil model as part of the gnomon (the portion that casts the shadow).

Each segment of the horizontal portion of the sundial is a geological period. Can you tell which periods are shown here?

Finally, I think this sculpture in the front garden entitled “Venus From The Ice Field” by Charles Herndon is ingenious. It is carved from a granite boulder found in the local glacial till.

My next post will be about the second museum — a very different place!

Wooster’s Fossil of the Week: A stromatoporoid (Middle Devonian of central Ohio)

October 30th, 2011

Stromatoporoids are very common fossils in the Silurian and Devonian of Ohio and Indiana, especially in carbonate rocks like the Columbus Limestone (from which the above specimen was collected). Wooster geologists encountered them frequently on our Estonia expeditions in the last few years, and we worked with at least their functional equivalents in the Jurassic of Israel (Wilson et al., 2008).

For their abundance, though, stromatoporoids still are a bit mysterious. We know for sure that they were marine animals of some kind, and they formed reefs in clear, warm seas rich in calcium carbonate (DaSilva et al., 2011). Because of this tropical habit, early workers believed they were some kind of coral, but now most paleontologists believe they were sponges. Stromatoporoids appear in the Ordovician and are abundant into the Early Carboniferous. The group seems to disappear until the Mesozoic, when they again become common with the same form and life habits lasting until extinction in the Late Cretaceous (Stearn et al., 1999).

The typical stromatoporoid has a thick skeleton of calcite with horizontal laminae, vertical pillars, mounds on the upper surface called mamelons, and dendritic canals called astrorhizae shallowly inscribed on the mamelons. These astrorhizae are the key to deciphering what the stromatoproids. They are very similar to those on modern hard sponges called sclerosponges. Stromatoporoids appear to be a kind of sclerosponge with a few significant differences (like a calcitic instead of an aragonitic skeleton).

Stromatoporoid anatomy from Boardman et al. (1987).

Top surface of a stromatoporoid from the Columbus Limestone showing the mamelons.

There is considerable debate about whether the Paleozoic stromatoporoids are really ancestral to the Mesozoic versions. There may instead be some kind of evolutionary convergence between two groups of hard sponges. The arguments are usually at the microscopic level!

The stromatoporoids were originally named by Nicholson and Murie in 1878. This gives us a chance to introduce another 19th Century paleontologist whose name we often see on common fossil taxa: Henry Alleyne Nicholson (1844-1899). Nicholson was a biologist and geologist born in England and educated in Germany and Scotland. He was an accomplished writer, authoring several popular textbooks, and a spectacular artist of the natural world. Nicholson taught in many universities in Canada and Great Britain, finally ending his career as Regius Professor of Natural History at the University of Aberdeen.

Henry Alleyne Nicholson (1844-1899) from the University of Aberdeen museum website.

References:

Boardman, R.S., Cheetham, A.H. and Rowell, A.J. 1987. Fossil Invertebrates. Wiley Publishers. 728 pages.

DaSilva, A., Kershaw, S. and Boulvain, F. 2011. Stromatoporoid palaeoecology in the Frasnian (Upper Devonian) Belgian platform, and its applications in interpretation of carbonate platform environments. Palaeontology 54: 883–905.

Nicholson, H.A. and Murie, J. 1878. On the minute structure of Stromatopora and its allies. Linnean Society, Journal of Zoology 14: 187-246.

Stearn, C.W., Webby, B.D., Nestor, H. and Stock, C.W. 1999. Revised classification and terminology of Palaeozoic stromatoporoids. Acta Palaeontologica Polonica 44: 1-70.

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.

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