Mark Wilson June 30th, 2011
KURESSAARE, ESTONIA–We have gotten to know the western coastline of Saaremaa very well and would like to simply share some of the gorgeous flowers found there. All of these grow in alvars, which are environments on limestone bedrock with thin and nutrient poor soils. They often dry out completely in the summer, so they tend to host endemic species well adapted to these specific conditions and generally out-competed elsewhere.
Saaremaa is especially blessed with plant diversity. There are 1200 species of vascular plants on the island, about 80% of all the vascular plant species in Estonia. About 10% of these species are rare and protected
I don’t have any identifications for these flowers. They are here for their beauty and as a break from all the rocks!
Mark Wilson June 28th, 2011
KURESSAARE, ESTONIA–Nick Fedorchuk began his fieldwork today at the Soeginina Cliff site we visited two days ago. The first thing we did was scout out the best place to measure the most complete section possible, and then we started the slow process of sampling and describing the rocks and fossils. On average we did about a meter an hour.
The above image shows one of the curious oncoids in the Soeginina limestones. Oncoids are usually almost spherical because they rolled around as bacteria formed layers around a nucleus. The oncoids in the lowermost Ludlow (Paadla Stage) here show an initial formation as spheroids and then they sat still on the seafloor and grew upwards to make little layered caps. The oncoid was knocked over occasionally and a new cap grew on top of the sideways oncoid. This finally made oncoids with multiple growth directions visible in cross-section.
Above is a bedding plane view of an oncoid-rich layer with shelly fossils. Some of the oncoids have formed around gastropod shells.
The trace fossils (evidence of organism behavior) are especially interesting because we can see them in bedding plane view (as above) and also in cross-sections. We will look at their distribution using various ichnofabric indices.
At the start of our day on the outcrop this happy Estonian dog joined the party. It stayed with us the whole time. It liked to splash around in the ocean and then joyfully jump on us — not conducive for taking notes or whacking rock samples, but fun nevertheless. Wolf (maybe the name we gave him was too easy) loves to gnaw on the carcasses of large, long-dead seabirds, bringing them to us as we worked. Wolf was sometimes a bit too exuberant, but he was a good friend for the day. We hope to see him tomorrow at the same place!
Mark Wilson June 27th, 2011
KURESSAARE, ESTONIA–Stromatoporoids are extinct calcareous sponges that were very common in shallow water environments of the Silurian. They are especially abundant in the middle Silurian of the Baltic Region. Today we visited a site called Katri Cliff where a reef composed of stromatoporoids is exposed. Olev Vinn is shown above studying them (with the inevitable remains of a Soviet coastal border guard post in the background).
Stromatoporoids made hard, dense skeletons of calcite, sequentially adding layers to them like onions. At Katri Cliff we found many examples of these sponges with rugose corals and tabulate corals embedded inside them. Apparently the sponge grew up around the coral skeletons, immuring them alive. The interesting question is whether the sponges and the corals had a mutual beneficial relationship or if they were actually competing for resources like space and food.
Stromatoporoid showing conical rugose corals in its skeleton.
Stromatoporoid broken in half and revealing an embedded tabulate coral.
We have placed this ancient reef on the list of possible projects for Rachel, but we won’t know what she is going to pursue until we visit the nearby island of Hiiumaa at the end of the week.
And in case you’re tired of so many fossils and seascapes in this blog, here’s another bit of history we saw today: Below are trenches built at the top of Ninase Cliff. The tragedy of 20th Century Estonian history is that we can’t immediately tell who dug these trenches. Was it Imperial Russians in 1917 defending against the invasion of Imperial Germans? Could they have been built by Soviets against the invading Nazis in 1941? Or maybe Nazis in 1944 fighting the re-invading Soviets? There is some satisfaction on this part of the coast to observe that the sea is slowly eroding these trenches back into the ancient limestone gravel from which they briefly appeared.
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!