Wooster’s Fossil of the Week: A mastodon tusk (Late Pleistocene of Holmes County, Ohio)

June 24th, 2012

This long and weathered tusk sits in a display case outside my office. It is from the American Mastodon (Mammut americanum) and was found many decades ago in Holmes County, just south of Wooster. A tooth found with it was a previous Fossil of the Week. Such tusks are rather rare because the ivory tends to disintegrate faster than tooth and bone. Our specimen is, in fact, hollow and held together by wires.
Above is a closer view of the proximal end of the tusk (the part closest to the face). You can see the hollowness and, curiously, that the ivory is charred. I used to tell students that the mastodon must have been hit by lightning, but I stopped when they took me too seriously!

This gives me a chance to mention a mastodon specimen I recently saw in a visit earlier this month to this famous place:
Monticello is, of course, the home of Thomas Jefferson, a Founding Father and the third president of the United States. Jefferson was a science enthusiast, and paleontology was one of his passions. He was fascinated with ancient life, and some have considered him the first American paleontologist. One room of the White House, for example, appears to have been devoted to his fossil bone collection.

Mastodons were particularly interesting to Jefferson because of an odd idea that was in vogue in France at the time. Georges-Louis Leclerc, Comte de Buffon, a famous French naturalist, wrote that “a niggardly sky and an unprolific land” caused life in the New World to be weak, small and degenerate. Life in North America was considered by the French to be quite inferior to that in Europe. Jefferson knew, of course, this was nuts. Having the bones of a North American elephant, as large or larger than any other elephants, would show the Frenchies how wrong they were. And Buffon eventually agreed, although he died before he could correct his books.
Above is a lower jawbone of Mammut americanum in Monticello. I wish I could have taken my own photograph, but this was not allowed. I’ve had to make do with one of their images online.

Curiously, Jefferson had one serious deficit when it comes to calling him a paleontologist. He apparently did not believe that species ever go extinct. When he dispatched Lewis and Clark on their expedition, for example, he expected them to find living mastodons deep in the American interior. Too bad they didn’t!

References:

Conniff, R. 2010. Mammoths and Mastodons: All American Monsters. Smithsonian Magazine, April 2010.

Semonin, P. 2000. American Monster: How the Nation’s First Prehistoric Creature Became a Symbol of National Identity. New York University Press, New York, 502 pages.

Thomson, K.S. 2008. The Legacy of the Mastodon: the Golden Age of Fossils in America. New Haven, Connecticut, Yale University Press.

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.

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 Fossils of the Week: Sponge and clam borings that revealed an ancient climate event (Upper Pleistocene of The Bahamas)

September 11th, 2011

This week’s fossils celebrate the publication today of a paper in Nature Geoscience that has been 20 years in the making. The title is: “Sea-level oscillations during the Last Interglacial highstand recorded by Bahamas coral”, and the senior author is the geochronological wizard Bill Thompson (Woods Hole Oceanographic Institution). The junior authors are my Smith College geologist friends Al Curran and Brian White and me.

The paper’s thesis is best told with an explanation of this 2006 image:
This photograph was taken on the island of Great Inagua along the coast. The flat dark surface in the foreground is the top of a fossil coral reef (“Reef I”) formed during the Last Interglacial (LIG) about 123,000 years ago. It was eroded down to this flat surface when sea-level dropped, exposing the reef to waves and eventually terrestrial weathering. The student sitting on this surface is Emily Ann Griffin (’07), one of three I.S. students who helped with parts of this project. (The others were Allison Cornett (’00) and Ann Steward (’07).) Behind Emily Ann is a coral accumulation of a reef (“Reef II”) that grew on the eroded surface after sea-level rose again about 119,000 years ago. These two reefs show, then, that sea-level dropped for about 4000 years, eroding the first reef, and then rose again to its previous level, allowing the second reef to grow. (You can see an unlabeled version of the photograph here.) The photograph at the top of this post is a small version of the same surface.

The significance of this set of reefs is that the erosion surface separating them can be seen throughout the world as evidence of a rapid global sea-level event during the Last Interglacial. Because the LIG had warm climatic conditions similar to what we will likely experience in the near future, it is crucial to know how something as important as sea-level may respond. The only way sea-level can fluctuate like this is if glacial ice volume changes, meaning there must have been an interval of global cooling (producing greater glacial ice volume) that lowered sea-level about 123,000 years ago, and then global warming (melting the ice) that raised it again within 4000 years. As we write in the paper, “This is of great scientific and societal interest because the LIG has often been cited as an analogue for future sea-level change. Estimates of LIG sea-level change, which took place in a world warmer than that of today, are crucial for estimates of future rates of rise under IPCC warming scenarios.” With our evidence we can show a magnitude and timing of an ancient sea-level fluctuation due to climate change.

Much of the paper concerns the dating techniques and issues (which is why Bill Thompson, the essential geochronologist, is the primary author). It is the dating of the corals that makes the story globally useful and significant. Here, though, I want to tell how the surface was discovered in the first place. It is a paleontological tale.

In the summer of 1991 I worked with Al Curran and Brian White on San Salvador Island in The Bahamas. They were concentrating on watery tasks that involved scuba diving, boats and the like, while I stayed on dry land (my preferred environment by far). I explored a famous fossil coral exposure called the Cockburntown Reef (Upper Pleistocene, Eemian) that Brian and Al had carefully mapped out over the past decade. The Bahamian government had recently authorized a new harbor on that part of the coastline and a large section of the fossil reef was dynamited away. The Cockburntown Reef now had a very fresh exposure in the new excavation quite different from the blackened part of the old reef we were used to. Immediately visible was a horizontal surface running through the reef marked by large clam borings called Gastrochaenolites (see below) and small borings (Entobia) made by clionaid sponges (see the image at the top of this post).
Inside the borings were long narrow bivalve shells belonging to the species Coralliophaga coralliophaga (which means “coral eater”; see below) and remnants of an ancient terrestrial soil (a paleosol). This surface was clearly a wave-cut platform later buried under a tropical soil.


My colleagues and I could trace this surface into the old, undynamited part of the Cockburntown Reef, then to other Eemian reefs on San Salvador, and then to other Bahamian islands like Great Inagua in the far south. Eventually this proved to be a global erosion surface described or at least mentioned in many papers, but its significance as an indicator of rapid eustatic sea-level fall and rise was heretofore unrecognized. Finally getting uranium-thorium radioactive dates on the corals above and below the erosion surface placed this surface in a time framework and ultimately as part of the history of global climate change.

This project began 20 years ago with the discovery of small holes left in an eroded surface by humble sponges and clams. Another example of the practical value of paleontology.

References:

Thompson, W.G., Curran, H.A., Wilson, M.A. and White, B. 2011. Sea-level oscillations during the Last Interglacial highstand recorded by Bahamas coral. Nature Geoscience (DOI: 10.1038/NGEO1253).

White, B.H., Curran, H.A. and Wilson, M.A. 1998. Bahamian coral reefs yield evidence of a brief sea-level lowstand during the last interglacial. Carbonates and Evaporites 13: 10-22.

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.

Wooster’s Fossil of the Week: A woolly mammoth tooth (Late Pleistocene of Holmes County, Ohio)

March 27th, 2011

Since we had a mastodon tooth as our last Fossil of the Week, paleontological symmetry demands we have a mammoth tooth this week. The fossil above also comes from the productive bogs of Holmes County a few miles south of Wooster.

Our tooth is from a young woolly mammoth (Mammuthus primigenius). These were true elephants, unlike the mastodons which were only distant cousins in another family. You can tell a mammoth tooth from a mastodon tooth by the flat ridges on its chewing surface rather than pointy cusps.

The woolly mammoth had long tusks (one of which we have in a display case outside my office) and, of course, plenty of long hair to keep it warm in the tundra environments it inhabited. They were grazers, apparently digging up grass and other ground vegetation with their tusks.

Mammuthus primigenius appeared about 150,000 years ago during the Pleistocene, and the last individual died surprisingly only 3700 years ago on a small Alaskan island. They are well known from frozen remains in Siberia — and from a new Japanese attempt to clone them from frozen tissue. (I’ve heard that one so many times …)

In June 2008, a Wooster Independent Study team saw cross-sections of mammoth footprints at The Mammoth Site, Hot Springs, South Dakota (see below). They could only be identified as such because of the dozens of mammoth skeletons around them!

Woolly mammoths in northern Spain (from a mural by Mauricio Antón).

Wooster’s Fossil of the Week: A mastodon tooth (Late Pleistocene of Holmes County, Ohio)

March 20th, 2011


Time for a vertebrate fossil from the College of Wooster paleontology collections.  Above is a side view of an American Mastodon tooth (Mammut americanum) from the Pleistocene of the county just south of us. It has been passed around through hundreds of student hands in our geology classes to demonstrate basic features of these large animals and their dietary habits. The image below shows their characteristic cusped chewing surface.


Mastodons looked like elephants but are actually in a separate family (Mammutidae instead of Proboscidea). They browsed diverse vegetation rather than grazed like elephants and mammoths. The American Mastodon roamed most of North America. They lived in herds in the cool woodlands, probably meeting final extinction under the spears of Paleo-Indians about 10,000 years ago.

My favorite reproduction of the American Mastodon is shown below. It is by the famous scientific illustrator Charles R. Knight (1874-1953). There is something very spirited as this young male charges into the scene. It even looks a bit like northeastern Ohio.

Plunging into Lake Manix

March 15th, 2011

ZZYZX, CALIFORNIA–East of Barstow and west of Afton Canyon was a very large pluvial lake during the Pleistocene. This Lake Manix was hundreds of feet deep, and its catastrophic drainage through Afton Canyon about 185,000 years ago must have been a great spectacle. This afternoon we explored one of the southern shores of this ancient lake, and then climbed down through its eroding bottom sediments.

Shoreline of Pleistocene Lake Manix. The dark rocks to the left apparently are remnants of an alluvial fan delta which extended into the lake shallows. The light-colored sediments below and to the right are from the lake itself. The white band in the foreground appears to be a type of coastal tufa formed by the agitated lake waters mixed with waters coming from the fan.

Lake Manix bottom sediments consisting mostly of fine silts and clays.

The plateau above the lake sediments includes windswept desert pavements and beautiful ventifacts (wind-carved stones) like this one.

Tunnels yet again — and a loess connection

August 13th, 2010

OPPENHEIM, GERMANY–This jewel of a town, with its large cathedral, half-timbered buildings and narrow streets, share surprising geological connections with Vicksburg, Mississippi — a city visited by Wooster geologists earlier this summer. Both are river towns which profited in good times as trade centers, and both are underlain by Pleistocene loess sediments. Loess is wind-deposited silt and clay that can be easily excavated yet retain vertical walls because of the angular nature of its grains. Residents of both cities dug caverns into their loess deposits to store goods and to escape the dogs of war above them.

Model of a family hiding in a loess cavern underneath Oppenheim, Germany.

Oppenheim is almost completely undermined by up to 200 km of connected tunnels and cellars known collectively as the Kellarlabyrinth. The digging began sometime in the Middle Ages as a way to safely store and transport goods between buildings in the prosperous town. When the religious wars of the 17th century began, Oppenheim was almost continually besieged and occupied by one side or the other. The labyrinth below became a good place to hide from marauding soldiers. The system continually grew as the Oppenheimers dug laterally through the thick bed of loess below their town. The tunnels are still in partial use today after renovation and structural enhancement. In 1945 the American Army successfully crossed the Rhine near Oppenheim. As one of General George Patton’s tanks moved through the streets of Oppenheim, it crashed through the street into a tunnel below. Heavy vehicles have been rerouted around Oppenheim ever since!

You can't have an extensive Medieval cavern system in Continental Europe without some part of it turned into an ossuary. There are the remains of at least 20,000 people in the Oppenheim bone caverns.

A bryozoan paradise in northern Japan

August 5th, 2010

Pleistocene bryozoan-encrusted cobble from Hokkaido, Japan. (All photos courtesy of Paul Taylor.)

KIEL, GERMANY–One of the most interesting presentations at this meeting of the International Bryozoology Association, at least to a paleontologist, was by my friend Paul Taylor (Natural History Museum, London). He described a fauna of bryozoans which inhabited cobbles in a cold-water submarine channel in northern Japan during the Pleistocene (roughly 0.50 to 1.25 million years ago). The cobble-bearing unit was exposed by tectonic action as dry land and forms a deposit colloquially known as “Kokemushi Paradise”.  Kokemushi is the delightful Japanese term for bryozoan.

One of the cobble-encrusting bryozoans under a scanning electron microscope. Note how many of the exquisite little spines are preserved in place.

There are 120 species of bryozoans on these igneous cobbles, which is an extraordinary diversity. Every cobble is encrusted, some with up to 25 species. There are also barnacles, corals, foraminiferans and serpulid worms. For a specialist in hard-substrate faunas (“sclerobionts“), this is a paradise indeed.

The vertical tubes are termed "peristomes" and they extend from the bryozoan apertures. Such delicate structures are rarely preserved in fossils.

When a limited hard surface like that of a cobble is occupied by diverse and abundant sessile organisms, there is inevitably a competition for living space. This competition is recorded in the fossil record by the overlapping of skeletons as one species overgrew another. The Kokemushi Paradise bryozoans show many examples of such space competition. It is not always a simple system of one species always overgrowing another. Sometimes two species will mutually overgrow each other.

A competitive system of overgrowth between two bryozoans.

The Kokemushi Paradise site is, alas, lost to development, but there are hundreds of cobbles preserved in the Natural History Museum in London. Maybe someday a Wooster Independent Study student will get the chance to examine them in paleoecological detail!

A Windy Desert Day for the Wooster Geologists

March 8th, 2010

ZZYZX, CALIFORNIA–The skies were brilliantly clear early this morning when we left the Desert Studies Center for points west. The price for the passage of the front was a stiff wind that kept up all day and even now is whistling in the darkness past our windows. I don’t mind at all.  It reminded me of delightful spring days in the desert when as kids we flew kites so high we could barely see them.

Our first stop was a visit to the extensive sedimentary layers laid down by the Pleistocene Lake Manix in what is now the lower Mojave River Valley.  We drove several miles on Harvard Road and walked across long stretches of desert pavement with ventifacts and occasional wind-polished agates.

Bottom sediments from the pluvial Lake Manix near Harvard Road. For scale, you may notice Megan Innis and Stephanie Jarvis in the central wash.

We then traveled farther west through Barstow to Owl Canyon and Rainbow Basin a few miles northwest of the city. There we met Buzz and Phyllis Sawyer, childhood friends of mine from Barstow and superb natural historians of the desert. We all enjoyed the diverse facies of the Barstow Formation (Middle to Upper Miocene) as well as the plants and animals in this protected area.

Professor Shelley Judge explains the complicated structure of Owl Canyon to her faculty colleagues using traditional geological hand language.

Wind-blown Wooster Geology field trip participants in Rainbow Basin with the famous Barstow Syncline in the background. This photograph was kindly taken by Buzz Sawyer.

Our last stop was Afton Canyon where we completed the Lake Manix story by looking at the outlet through which it catastrophically drained into Soda and Silver Lakes to the east. The sun had set by the time we gathered back at the vans, ending another productive and thought-provoking field day.

Wooster geologists crossing the mighty Mojave River in Afton Canyon. We don't think this is quite the same river Jedidiah Smith encountered.

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