Archive for August, 2010

Tunnels (again)

August 9th, 2010

MAASTRICHT, THE NETHERLANDS–After mentioning the excavations in the Maastricht Formation limestones (latest Cretaceous) in the last post, I expected to be moving on the next day to a quarry. I hadn’t read the guidebook closely enough: we were planning to spend the afternoon in them! Thinking of my last geology-in-tunnels experience in Russia, I was a bit apprehensive. This time, though, the tunnels were relatively dry, much wider and taller (no sliding on your belly for 30 feet!), and far more stable.

A portion of the tunnel map painted on a wall near the entrance.

The tunnels under Maastricht are incredibly complex, the product of hundreds of years of mining. The walls often show charcoal drawings of amazing complexity, some dating back to the 17th Century. On our particular route was a Roman Catholic chapel fashioned out of a few galleries by painting the rock walls, adding statuary and carving a pulpit. It was a refuge for the Catholic community when revolutionary French soldiers took over the town at the end of the 18th Century.

Our tour had a geological purpose. We saw, in three dimensions, what may be the most complete Cretaceous-Paleogene boundary known. I learned a great deal about the end-Cretaceous extinction event, especially that the story is getting more complex and surprising. More on that in a later post.

Geology and Art History

August 9th, 2010

Tunnels in the Maastrichtian Formation (Late Cretaceous) in Maastricht, The Netherlands. Location = N50.82667°, E5.67978°.

MAASTRICHT, THE NETHERLANDS–The tunnels dug into the soft Maastrichtian Formation limestones in this city have a long history starting with the Romans. At first the excavations were intended only to extract building stone, but with all the battles, sieges and other military actions in this region, residents realized that these dry and deep caves also provided places of refuge. Bakeries, chapels, storehouses and dormitories were constructed in these spaces for times of war since the Middle Ages.

During World War II, the Dutch hid several works of art in these tunnels to protect them from the Germans. These included the magnificent Night Watch by Rembrandt and The Street by Vermeer. They were guarded by Dutch military police successfully throughout the occupation. We can view this art today because of the extent, thickness and composition of this Cretaceous limestone sequence — and the courage of Dutch patriots.

Rembrandt's The Night Watch (from Wikipedia).

Wooster Geologist in The Netherlands

August 8th, 2010

An outcrop of the Type Maastrichtian in Maastricht, The Netherlands. The square tunnels were dug in the Middle Ages for building stone. The rock is a limestone.

MAASTRICHT, THE NETHERLANDS–This is the first day of the International Bryozoology Association post-conference field trip. We took a train south from Kiel to Hamburg, Germany, and then connected with another train to Cologne. After spending a half-hour at the Cologne Cathedral (right next door to the train station), we took a bus west to Maastricht, The Netherlands, on the Maas River. We then spent the rest of the day in the ENCI cement quarry exploring the very fossiliferous Maastricht Formation, which is the type section of the Maastrichtian Stage described yesterday.

One of my favorite fossils in the Maastricht quarry. This is an external mold of an aragonitic shell in which the borings were filled with calcitic sediment. The result is a set of casts of the original borings.

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

August 7th, 2010

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!

International Bryozoology Association meeting ends, field trips begin

August 6th, 2010

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!

Cretaceous soft-bodied bryozoans from the western USA

August 6th, 2010

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.)

On giving a professional presentation

August 6th, 2010

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.

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!

The advantages and disadvantages of building your city on clay

August 4th, 2010

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.

Kiel Fjord and Canal, northern Germany

August 3rd, 2010

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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