Mark Wilson June 26th, 2011
KURESSAARE, ESTONIA–It is always a joy to begin the fieldwork for an Independent Study project — or at least know what the fieldwork will be. This morning we visited the Soeginina Cliff locality on the Atla Peninsula of western Saaremaa and it was all we hoped it would be. Nick Fedorchuk (pictured above as a happy man with his outcrop) studied the literature about this locality during his Junior Independent Study period last semester. We confirmed today that the rocks are indeed auspicious and will work as the basis of his research.
This locality is significant because it records a time and rock boundary in the geological record. The lower portion belongs to the Wenlock Series in the Silurian System, and the upper portion is in the Ludlow Series of the Silurian. They are separated by a disconformity (an erosional horizon indicating a hiatus in the geological time record). Boundaries such as this are always interesting because they can be correlated across the globe with other rocks formed at the same time. We want to better understand what was happening in Baltica at this junction between the Wenlock and Ludlow, and then compare it to the equivalents in Sweden, Britain and North America.
The boundary rocks show a laminated unit in the uppermost Wenlock (Rootsiküla Stage) that has been interpreted as lagoonal in origin, and then a more massive limestone in the lowermost Ludlow (Paadla Stage) with oncoids (microbial accumulations) and eventually shelly beds thought to be more open shallow marine deposits. The division between them appears to be marked by a mineralized layer (see image below). Later Nick will collect rock and fossil samples to thoroughly describe this interval and sharpen the paleoenvironmental and paleoecological hypotheses.
Rachel Matt (below) does not yet know which outcrop will be the focus of her research, but we will soon!
Our last visit of the day was to Kaarma Quarry and its exposed laminated lagoonal limestones and dolomites of the Ludlow. You can see below the team in action — and what a beautiful day it was.
Mark Wilson September 29th, 2010
CHRISTCHURCH, NEW ZEALAND–Wooster geology student Andrew Collins has once again visited a fascinating geological locality in New Zealand. He is certainly getting his semester’s worth of adventures, from earthquakes to glaciers. Please visit his blog and see additional photos and descriptions of his trips.
Kaikoura Canyon and associated peninsula and mountains. From: http://www.janesoceania.com/newzealand_kaikoura/index.htm
This time Andrew came about as close to the trench of a subduction zone as is possible without getting wet. He journeyed to Kaikoura on the South Island north of his university base at Christchurch. This town is at the base of a peninsula and squeezed between mountains and the coast. Just a few hundred meters offshore is a deep trough (Kaikoura Canyon) marking a trench where part of the Pacific Plate is being subducted beneath New Zealand, producing volcanoes. The trough also forms an oceanic upwelling system that nourishes phytoplankton which in turn are the primary producers for a diverse and abundant community of organisms culminating with seals and whales. Geologists love to visit active places like this — but we don’t buy real estate there!
Andrew noted the uplifted limestones along the peninsula. These are Late Cretaceous in age, adding to the Cretaceous theme in this year’s blog entries. (Click “Cretaceous” in the tag cloud to the right and see.)
Upifted Upper Cretaceous limestones along the Kaikoura coast, New Zealand. Photo by Andrew Collins.
Tectonic fabric exposed in Upper Cretaceous limestones along the Kaikoura coast, New Zealand. Photo by Andrew Collins.
The Southern Alps, surf and a gravelly beach near Kaikoura, New Zealand. Note the low beach ridges formed by storm waves. Photo by Andrew Collins.
Mark Wilson 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.
Mark Wilson 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).
Mark Wilson 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.
Mark Wilson July 13th, 2010
CHRISTCHURCH, NEW ZEALAND–And it’s not me! Wooster geology student Andrew Collins is in a study abroad program on the South Island of New Zealand. He has promised to share with us his geological experiences now and then. Andrew recently traveled to a town called Springfield near Christchurch and visited some amazing Paleogene limestone exposures on Castle Hill. This is an extreme example of karstic weathering.
Paleogene limestone on Castle Hill, South Island, New Zealand. Photograph by Andrew Collins.
Beautiful, eh? Andrew will share more New Zealand geology with us through this blog and his own.
This summer we’ve had Wooster geologists in Alaska, the southern USA, Ohio, Israel, Iceland and Utah … and we’re only halfway through our field season. Gotta love it!
Mark Wilson December 16th, 2009
CAESAR CREEK STATE PARK, OHIO–I’ve definitely extended my field season as far as possible. (And what a season it has been.) My last fieldwork at the end of this research leave was in Ohio, about three hours south of Wooster. I visited Caesar Creek State Park this morning where a large cut through an Upper Ordovician section has been set aside as a fossil preserve of sorts. It is an emergency spillway for Caesar Creek Lake, which is maintained by the US Army Corps of Engineers. Many Wooster paleontology field trips have stopped here. Fossils can be collected, but only with a permit (obtained at the visitor center) and following significant regulations. The fossils are diverse and abundant, including all the stars of the Ordovician seafloor.
My task was to find, photograph and measure an old trace fossil friend: the boring Petroxestes pera. This is a slot-shaped excavation in carbonate hard substrates formed by bivalves (probably in this case the modiomorphid Corallidomus).
The boring Petroxestes pera (the name means "purse-shaped rock-grinding") in a hardground at Caesar Creek State Park.
These elongated holes are among the first bivalve borings. Some of my students and I think they may have been formed in clusters, and they also may be oriented relative to each other and their local environment. In any case, I found plenty. It was an astonishingly cold morning, though, so I didn’t waste any time on the outcrop!
Yes, this photo is here mainly to show just how tough Wooster Geologists are. And there are some very nice brachiopods and bryozoans!
Mark Wilson December 15th, 2009
MAYSVILLE, KENTUCKY–Our short geological expedition to northern Kentucky today was to look at some odd blocks of limestone that sit suspended in the sediments as if they were dropped in while the sequence was accumulating.
An eroded, bored and encrusted limestone block in the Fairview Formation (Upper Ordovician) of northern Kentucky at the Route 11 outcrop (N38.61243°, W83.75575°).
These rocks are bored by worms and encrusted by bryozoans on their top and sides, and they often sit at high angles to the surrounding strata.
Bryozoans encrusting a side of the block above. The beautiful pinkish bryozoan on the left is the holdfast of a ptilodictyoid which in life held an erect bifoliate portion of the colony. The field of view here is about 10 cm wide.
It is difficult to imagine a mechanism which deposited large, lithified limestone blocks in the middle of a shallow carbonate ramp. They are almost certainly related to “seismite” structures in the outcrop (see next post), but how these earthquakes would have transported such rocks is a mystery. We also do not know how quickly the limestone had been lithified before emplacement. We do know that the sides of these blocks were exposed on the seafloor long enough to accumulate encrusters and borers.
Plenty yet to discover in these well-studied rocks. It is a continuing lesson for scientists: the more you see the more questions you have.
Mark Wilson December 15th, 2009
MAYSVILLE, KENTUCKY–Today I visited the University of Cincinnati for a meeting of Aaron House’s thesis committee, on which I serve. (Aaron is a 2004 geology graduate from The College of Wooster.) It all went very well and soon after Aaron took me and two other geologists on a short field trip to an Upper Ordovician outcrop near the Ohio River town of Maysville.
Outcrop of the upper Fairview Formation (Upper Ordovician) on Kentucky Route 11 near Maysville, Kentucky (N38.61243°, W83.75575°). A distant Aaron House for scale.
Many Wooster students and alumni will immediately recognize all the elements of a typical roadside outcrop of the Cincinnatian Group in winter: gray rocks matching the gray sky, the muddy ditch at the base, and the thin verge of grass extending to the road. Alternating limestones, siltstones and shales give the outcrop its jagged appearance.
Some of the best Ordovician fossils in the world are found in these sedimentary sequences, and the stratigraphy holds many mysteries despite over a century and a half of intensive study by geologists. Wooster students have completed dozens of Independent Study theses with these rocks, and there are many more to come. Aaron House is now pursuing a masters degree by assessing and interpreting the preservation of mollusk fossils in the Cincinnatian.
Mark Wilson July 8th, 2009
View from my room in the St. Barbara Hotel, downtown Tallinn, Estonia (N59.431802°, E24.743355°).
The Wooster Geology Estonia team is now safely in Tallinn preparing for our visit to the paleontological collections in the university museum tomorrow. For me a private joy is that our hotel building is made of Ordovician limestone, the very same stone that I studied a month ago in Russia.