The power of biostratigraphy: the Campanian-Maastrichtian boundary in the Late Cretaceous

Mark Wilson August 7, 2010 12:10 pm

Chalk quarry I visited today near Lägerdorf, Germany. It is Late Cretaceous in age, spanning the Campanian-Maastrichtian stage boundary. Location: N53.90395°, E9.57840°.

Outcrop of the Pierre Shale in South Dakota visited two years ago by a Wooster Geology team. It is also Late Cretaceous and at the Campanian-Maastrichtian stage boundary.

KIEL, GERMANY–Comparing the two very different geological sections pictured above, you should ask how we know that they are precisely the same age. After all, they are thousands of miles apart and are quite different in their composition and fossil content. We can even say that the boundary between the Campanian and Maastrichtian stages (these are fine divisions of geological time) is 70.6 million years old, give or take a hundred thousand years or so. The answer starts with the belemnite fossil Belemnella lanceolata, a nice example of which we found today in the German chalk quarry:

A belemnite is an extinct cephalopod (a group which includes the modern squid, octopus and others) that is a common fossil in Mesozoic sediments, especially in the Jurassic and Cretaceous Periods. They were swimming predators and so they could live happily in oceanic and shelf waters with little regard for the sediments beneath them. They are thus found in a variety of sedimentary rocks around the world. Belemnella lanceolata is present throughout Europe in a narrow time interval bounded by its origination and extinction. It overlaps in its age range with a variety of other fossils in a chain of co-occurrences that eventually includes Baculites baculus of South Dakota. Because these fossil species evolved and went extinct at specific times, correlation links them together through a particular time interval. Geologists decided that the first appearance of Belemnella lanceolata would be the marker for the base of the Maastrichtian Stage (and by implication the top of the Campanian Stage). Thus we use paleontology and evolution to mark time in the rock record and correlate these time units around the world. For more details on this story you can check out the massive Late Cretaceous correlation chart (a colorful pdf) hosted by Purdue University.

How do we know this boundary is 70.6 million years old, more or less? That is another story of volcanic ash falls, igneous rocks, and radioactive dating. Maybe later!

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International Bryozoology Association meeting ends, field trips begin

Mark Wilson August 6, 2010 3:03 pm

KIEL, GERMANY–The 15th meeting of the International Bryozoology Association ended this afternoon with the usual giving of awards, assessing the budget, and planning the next meeting (Sicily in 2013). I like this group very much. It is the best combination of biologists and paleontologists I know. (A larger version of the official photograph by Andrej Ernst is available.)  The field trips begin tomorrow!

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Cretaceous soft-bodied bryozoans from the western USA

Mark Wilson August 6, 2010 2:30 pm

KIEL, GERMANY–I gave my presentation to the International Bryozoology Association meeting this afternoon. It was a fun project because it involved two of my favorite things: working with Paul Taylor from the Natural History Museum and advising an Independent Study student, in this case John Sime. I’ve repeated three of the slides below. The entire set of PowerPoint slides is no farther than a click away.

(Abstract in Terra Nostra – Schriften der GeoUnion Alfred Wegener-Stiftung, vol. 2010/4, p. 47.)

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On giving a professional presentation

Mark Wilson August 6, 2010 1:46 pm

The lecture hall at the University of Kiel used for the 2010 meeting of the International Bryozoology Association.

KIEL, GERMANY–There is an exquisite moment as you wait in the darkened hall for your turn to speak. The presenter just before finally says something like, “in conclusion …” Even though you knew this time had to come, your heart speeds up, your vocal cords tighten, and you feel the rush of new adrenaline.

You remember how easy it was to respond to the invitation months ago and submit that abstract. You thought nothing of it for weeks, even after making all the travel arrangements and seeing your name in the program. Then about a week before the talk came a twinge of anxiety — maybe this won’t be as easy as I think? Furious action for a day as you prepare the PowerPoint slides and run through them a few times. Yes, that’s good. With relief you store it on a thumbdrive and feel accomplished.

The meeting starts and you sit through the first set of presentations. Hey, most of these talks are very good! Listening to the questions you realize it is time to up your game. The night before the talk is always when the strongest doubts settle in and you look at your simple set of slides and obsessively begin to add, subtract, redraft, rearrange. The morning of the talk is devoted to nervous pacing and absent-minded mistakes. (Today, for example, I walked a half-hour towards the university and had to go back for my wallet.)

Once your presentation slides are loaded in the computer projection system, a deep calm descends. The die is cast, your fate is set.

Standing on the stage with the microphone in place and the first slide displayed always feels like an out-of-body experience. You hear yourself begin to talk but somehow your consciousness has split free and is running an independent narration. How’s he going to do?, the observer asks. He seems to be going a bit fast there. Steady that laser pointer. There’s a man in the back with a laptop open. Is it raining outside? All the while the speaker speaks on.

Everything is going well enough. No blank pauses, no stumbling with words. Still within the time limit. Almost to the last slide … keep talking …

Fire alarm!

And not just any fire alarm. This is a heavy-duty German version with blaring horns and flashing lights. It is so loud that it silences even the narrator. The audience sits stunned by the noise, waiting for instructions. None can come because no one would hear them. A few people stand up and head to the doors, and soon everyone follows. I take off the microphone and go along. Only one minute left and I would have been fully released!

It was, of course, a false alarm, but it involved two fire engines and their crews. Two hours later we reassembled and I presented the last minute of my paper, which was a bit of an anticlimax. You’re lucky, people told me, for we will all remember your talk — or, rather, that you were the one who was talking.

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A bryozoan paradise in northern Japan

Mark Wilson August 5, 2010 6:50 am

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!

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The advantages and disadvantages of building your city on clay

Mark Wilson August 4, 2010 3:36 pm

Lübeck, Germany–Do not adjust the image above. It is of the Holstein Gate (“Holstentor”) on the western side of the Free and Hanseatic City of Lübeck. On the left is a side view and the right is from the front. It is a double-towered medieval gate which has suffered some serious tilting because its foundations (one under each tower) were built on glacial clays in marshy terrain. It is an emblematic German structure (it is on a commemorative German two-euro coin) and northern Europe’s equivalent to the Leaning Tower of Pisa.

The advantages of building a city on clay? This is what they use to make the bricks!

The Marienkirche in Lübeck. This is one of the tallest brick churches in the world. It was heavily damaged during an air raid in 1942 and has been massively reconstructed.

A riverside view of western Lübeck. Brick is still the predominant building material. Prewar buildings often stand surrounded by newer structures which filled in the bomb damage.

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Kiel Fjord and Canal, northern Germany

Mark Wilson August 3, 2010 11:47 am

The very southern end of the Kiel Fjord. Not the most attractive geological photograph, but the best I can do so far!

KIEL, GERMANY–Geologists always try to see the geological context of cities they visit, usually by studying the form of the landscape (“geomorphology“) and peering under bridges and the like to find exposed rocks. I have been notably unsuccessful at this here in Kiel. The asphalt lies heavy on the city, and the slopes are gentle. Kiel, however, has a very geological reason for its existence: it surrounds the end of a deep fjord of the Baltic Sea.

A fjord is a long, narrow valley carved by glaciation and then flooded by the sea. The Kiel Fjord was cut from south to north toward the ancient Baltic Sea during the Late Pleistocene. The Kiel Fjord was originally settled by Vikings who found it to be a convenient base to berth their ships as they pillaged the countryside. By the Middle Ages it was an important German port well protected from storms and attack because the deep water penetrated so far inland.

The Kiel Fjord from Google Earth.

The Kiel Canal is an extraordinary waterway which connects the Kiel Fjord (and thus the Baltic Sea) to the North Sea. It was completed in 1885. One of its first uses was to allow the German Navy to bypass the complicated (and stormy) Jutland Peninsula when passing from the Baltic to North Seas. It was enlarged between 1907 and 1914 so that large battleships (Dreadnoughts) could pass. This greatly concerned the British and was one of the many tensions which led to World War I.

The entrance to the Kiel Canal from the Kiel Fjord, magnified from the above Google Earth view.

Tomorrow we have our first field trip of the meeting, so I expect to be able to report on more geological scenery of northern Germany. At least I can show you now some German food!

Pickles!

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Christian Albrechts Universität zu Kiel (our IBA meeting venue)

Mark Wilson August 2, 2010 8:03 am

KIEL, GERMANY–It is always interesting for an academic to visit another college or university … and we get many opportunities. The International Bryozoology Association meeting is being held at the Christian Albrechts Universität zu Kiel (University of Kiel for most English speakers) in northern Germany. It was founded in 1665 and later became one of the most important universities in Prussia. It presently has 23,000 students and a strong science program.

You may ask why such an old university has no buildings built before 1945? You know the answer. The original campus was heavily bombed in World War II. (Kiel was an important German naval base, especially for U-boats.) This new campus was moved to another location where the only signs of the old are occasional relics like the statue below.

Statue of Aristotle on the pre-1945 campus (left); same statue pulled from the wartime rubble and displayed on the new campus.

The Geology Department here has a small museum with a modern design featuring lots of natural light. It is a very pleasant and quiet place to have a meeting such as this.

Geology museum at the University of Kiel with glass walls facing east.

A Silurian reef display from Gotland, Sweden. This is very similar to the reefs Wooster students worked with in Estonia last year.

A modern lava pillow for Meagen and other petrologists. "Aus 2700 m Tiefe mit Fernsehgreifer geborgen, Mittelatlantischer Rücken nördlich Jan Mayen."

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Stony bryozoans get their day

Mark Wilson August 1, 2010 2:52 pm

Trepostome ("stony") bryozoan on a carbonate hardground from the Kanosh Formation (Ordovician, Whiterockian) of west-central Utah.

KIEL, GERMANY–The first day of the International Bryozoology Association meeting is traditionally devoted to workshops where participants can listen to experts on a particular group, technique or idea and then ask questions, work out exercises, or study specimens. I went to the workshop on a group of extinct bryozoans called trepostomes. The Order Trepostomata usually produced thick skeletons of the mineral calcite so they are commonly known as “stony bryozoans”. They lived from the Ordovician into the Triassic, and then disappeared forever. They are a difficult group to work with because their diagnostic features are internal and microscopic (thus requiring thin-sections or acetate peels to identify) and the number of important defining characters is still debated. I went to this workshop because Ohio can be considered the Trepostome Capital of the World with its abundant and diverse varieties found in the Ordovician of the Cincinnati area. Any Wooster geology student who has taken the Invertebrate Paleontology course will remember the buckets of these fossils we’ve collected over the years on field trips.

Wooster played a small role in this workshop, to my delight. One of the interesting and somewhat odd trepostome bryozoan types is found in the Ordovician (Whiterockian) at a place called Fossil Mountain in the western desert of Utah. A generation of Wooster Independent Study students worked here with me studying carbonate hardgrounds and the fossils associated with them. We collected many examples of a strange bryozoan we called “Trepostome Species A” because we could not identify it. Later Andrej Ernst, Paul Taylor and I described it as a new genus: Kanoshopora. It is still odd with its variable walls and colony forms. This meeting may have stirred some interest in pursuing its functional morphology (essentially how it lived) and evolutionary placement. A nice contribution from those days in the late 20th Century when we walked up and down the sunny slopes of Fossil Mountain trying to sort it all out.

Longitudinal thin-section view of Kanoshopora droserae showing its complex zooecial walls.

Fossil Mountain, west-central Utah -- the scene of much Wooster geology Independent Study fieldwork in the 1980s and 1990s, and the home of many of the oldest and strangest trepostome bryozoans.

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Wooster Geologist in Germany

Mark Wilson July 31, 2010 1:35 pm

View of Hamburg, Germany, where my meeting began with a one-day walking tour. This is a view from the very, very high steeple of the St. Michaelis Church. It is reached by climbing, many, many steps -- the open kind where you can see the yawning chasm below you as giant bells rattle the rivets.

KIEL, GERMANY–One of the many joys of being a geologist is attending international scientific meetings. They are always in some location that is convenient for travel and has local field areas the participants want to visit. I am here in northwestern Germany attending a meeting of the International Bryozoological Association. This is an organization that studies, naturally enough, the Phylum Bryozoa, and it includes biologists and paleontologists. Our meetings are remarkably seamless sessions that switch between living and fossil organisms. While I’m certainly not a hardcore bryozoologist, I work with the critters often and very much enjoy learning more about their evolution and ecology.

For this meeting the field areas are diverse and spectacular.  For the biologists there are extensive tidal flats and shallow marine shelf areas on the Baltic coast, and for the paleontologists there are numerous quarries into very fossiliferous Cretaceous chalks. After the meeting I am going on a week-long field trip through western Germany where we will see rocks and fossils from the Devonian through the Miocene. Bryozoans will be a theme, of course, but we will see additional fossil groups, sedimentary structures, folds, faults, dikes and many other things that make the hearts of geologists beat faster. You can count on seeing many images and stories posted here when possible!

Bryozoans from an oil shale in the Ordovician of Estonia, just to put you in the right mood. Anyone who has had a paleontology course will tell you that bryozoans are among their favorite fossils.

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