An intricate Silurian stromatoporoid reef on the island of Saaremaa, Estonia

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.

A new Senior Independent Study project begins in Estonia

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.

Wooster Geologists return to Estonia

June 25th, 2011

KURESSAARE, ESTONIA–Yesterday afternoon three Wooster geologists met in the Tallinn, Estonia, airport within an hour after flying from three different countries. (Thank you, travel agent Suzanne Easterling!) We rented a car and then drove through impressive rainstorms westwards to the coast where we boarded a ferry for the island of Saaremaa. By dinner time we had checked into a little hotel in the small city of Kuressaare. We are the third team of Wooster geologists to work in Estonia. The last one was two years ago — one of the first expeditions covered by this blog.

This morning we began our field reconnaissance with our friend and colleague Olev Vinn (shown below) of the University of Tartu. Olev is generously working with us for a week as we explore the Silurian and sort out Independent Study projects for senior geology students Nick Fedorchuk and Rachel Matt (pictured above). They are already prepared for work at particular sections, but we first want an overview of the Silurian on the island (and to be ready for surprises).
The Silurian of Saaremaa and its sister island Hiiumaa is very well exposed along the coastline in a series of cliffs (some of which, admittedly, are less than two meters high!). They encode information about the environments and communities on the ancient continent of Baltica about 430 million years ago. Saaremaa is particularly interesting to us because it was essentially off-limits to visitors between 1940 and 1991 because it was a military zone occupied by Soviets, and then Germans, and then Soviets again until Estonia regained its independence upon the collapse of the Soviet Union. The rocks and fossils here have not been studied as intensively as their equivalents elsewhere in Europe, so there are many opportunities for new discoveries and interpretations.
Today we visited Abula Cliff, Jaagarahu Quarry, and Elda Cliff on the western extension of the island looking at limestones and dolomites of the Wenlock Stage. Spherical stromatoporoids (see above) caught our fancy because they were particularly well exposed at Abula Cliff.

As you can see from the photos it was a gorgeous day. More geology tomorrow!
An old Soviet searchlight station at Elda Cliff (N58.30450°, E21.82935°). For twenty years now this coastline is free!

Wooster’s Fossil of the Week: A chain coral (Silurian of Ohio)

June 19th, 2011

For some reason the Fossil of the Week I’ve had the most comments about is the Ordovician honeycomb coral from Indiana. It has an unexpected polygonal symmetry reflected in many other geological materials like desiccation cracks and columnar basalt. So this week’s fossil is another coral with a surprising shape: the chain coral Halysites.

Halysites is a tabulate coral genus originally named by Johann Fischer von Waldheim in 1828. Its corallum (colonial skeleton) consists of long vertical tubes (corallites) laterally attached to each other in ranks so that a cross-section looks like a series of chain links. Each corallite held a single coral polyp (an individual) that collected zooplankton for food. The spaces between the ranks — the empty holes — are called lacunae.

A closer view of the halysitid corallum. This specimen is replaced with silica so the surrounding limestone matrix could be removed by dissolving it in hydrochloric acid.

Halysites lived only in the Ordovician and Silurian (about 480 to 420 million years ago), so it is a rough index fossil for these periods. They were especially common in coral reefs, adding stability because their lacunae filled with sediment making them very difficult to dislodge by currents.

Thin-section of a halysitid coral with limestone matrix still in the star-shaped lacunae.

References:

Motus, M.-A. and Klaamann, E. 1999. The halysitid coral genera Halysites and Cystihalysites from Gotland, Sweden. GFF 121: 81-90.

Christian Albrechts Universität zu Kiel (our IBA meeting venue)

August 2nd, 2010

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."

Paleoenvironmental analysis of the Silurian Jaani Formation on the island of Saaremaa, Estonia (Senior Independent Study Thesis by Rob McConnell)

February 18th, 2010

Editor’s note: Senior Independent Study (I.S.) is a year-long program at The College of Wooster in which each student completes a research project and thesis with a faculty mentor.  We particularly enjoy I.S. in the Geology Department because there are so many cool things to do for both the faculty advisor and the student.  We are now posting abstracts of each study as they become available.  The following was written by Rob McConnell, a senior geology major from Darby, Montana.  Here is a link to his final PowerPoint presentation on this project.

In the summer of 2009, Wooster paleontologists Dr. Mark Wilson, Palmer Shonk, and I traveled to Estonia with fellow Ohio State University paleontologist Dr. Bill Ausich. Olev Vinn of the University of Tartu greeted us at the Tallinn Airport. We then proceeded by car to the island of Saaremaa in western Estonia. The city of Kuressaare would serve as our home for the next week as we conducted our research on the island.

My research describes two members of the Jaani Formation (Silurian, Wenlock): the older Mustjala Member and the younger Ninase Member. Samples of these two members were collected from three sites along the northern Saaremaa coast:  Liiva Cliff, Suuriku Cliff, and Panga Cliff (Figure 1).

Figure 1. Jaani Formation at Panga Cliff, Saaremaa, Estonia.

Figure 1. Jaani Formation at Panga Cliff, Saaremaa, Estonia.

The purpose of my research is to describe and recreate the paleoenvironment of the Jaani Formation. I am doing this by analyzing thin-section slides, stromatoporoid sponges (Figure 2), and various other fossils such as corals and brachiopods. It appears thus far that the lower Mustjala Member is far more fossiliferous and contains larger stromatoporoids, many of which are still in life position. This indicates a tranquil shallow marine environment. Smaller and flatter sponges are found in the upper Mustjala Member, close to the Mustjala/Ninase boundary. This is likely because of a shallowing of the water through time (a regression).

Figure 2. Stromatoporoids from the Mustjala Member, Jaani Formation (Silurian, Wenlock) on Saaremaa, Estonia.

Figure 2. Stromatoporoids from the Mustjala Member, Jaani Formation (Silurian, Wenlock) on Saaremaa, Estonia.

The Ninase Member has different characteristics than the Mustjala. In general, it is better cemented and contains fewer fossils. It also contains more brachiopods and fewer sponges. It may have been deposited in a higher energy environment. Continued analysis of both members is required to gain a better understanding of this approximately 420 million year old environment.

Paleoenvironmental Reconstruction of the Late Silurian (Pridoli) Äigu Beds of Saaremaa Island, Estonia (Senior Independent Study Thesis by Palmer Shonk)

February 15th, 2010

Editor’s note: Senior Independent Study (I.S.) is a year-long program at The College of Wooster in which each student completes a research project and thesis with a faculty mentor.  We particularly enjoy I.S. in the Geology Department because there are so many cool things to do for both the faculty advisor and the student.  We are now posting abstracts of each study as they become available.  The following was written by Palmer Shonk, a senior geology major from Dublin, New Hampshire.  Here is a link to his final PowerPoint presentation on this project.

I traveled to Estonia in July of 2009 with my advisor, Dr. Mark Wilson, Dr. Bill Ausich of The Ohio State University, and fellow Wooster geology major Robert McConnell. Upon arrival, we were greeted by Dr. Olev Vinn, his wife Ingrid, and their baby daughter. Olev is a geology professor at Tartu University in Estonia. The seven of us then headed for the island of Saaremaa, where I carried out my research. We stayed in the town of Kuressaare, on the southern shore of the island. My field site, the Äigu Beds, is about a 20 minute drive southwest of Kuressaare, on the western shore of the Sõrve Peninsula.

The Äigu Beds (Figure 1) are part of the Kaugatuma formation, named after the nearby town of Kaugatuma. My goal is to use the fossils and lithology at the beds to reconstruct an environment 418 million years old. My group assisted me in collecting fossils from three distinct layers. The first layer, about 8 cm thick, is an argillaceous limestone and contains many fossils still in life position, particularly crinoid holdfasts (Figure 2). This layer represents a calm, shallow-marine environment with soft, submarine dunes. The second layer, about 17 cm thick, shows evidence of a high energy event such as a storm. Fossils in the second layer have been crushed and are cemented together. The third layer, about 30 cm thick, is comprised again of the argillaceous limestone of layer one, but also shows evidence of a small scale high-energy event due to its “mashed” fossil specimens.

Figure 1. Part of the Äigu Beds on Saaremaa Island, Estonia; Late Silurian in age; note green pen for scale.

Figure 1. Part of the Äigu Beds on Saaremaa Island, Estonia; Late Silurian in age; note green pen for scale.

Figure 2. Crinoid holdfast from the first layer at the Äigu Beds; note tip of pen for scale.

Figure 2. Crinoid holdfast from the first layer at the Äigu Beds; note tip of pen for scale.

The wonder of natural history museums

July 9th, 2009

TALLINN, ESTONIA–Scientific museums preserve specimens and information from generations of researchers, collectors and students. The interiors of a typical paleontological museum contains windowless rooms filled almost to the ceiling with cabinets, each with dozens of drawers containing carefully labeled and cataloged specimens. Because information grows rapidly in science, the most important information on those labels is not the identity of the fossils but where they were found. The names and even systematic categories often change over the years as we learn new characteristics of particular groups, but the location information will always be critical for the value of the specimen for future researchers.

Today we visited the Institute of Geology at the Tallinn University of Technology. We were hosted by Dr. Helje Pärnaste, a paleontologist who specializes in Ordovician trilobites. She generously spent the day with us going through the collections. Using one of the best electronic cataloging systems we have ever seen, she was able to take us to drawers containing specimens from our study localities. We were able to add to our faunal lists and see better preserved fossils which will help in our future identifications. We concentrated on crinoids, of course, and were able to calibrate what we found which was truly new and see many other examples.

The Estonia Geology Research crew examining specimens in the Institute of Geology collections (left); a typical museum drawer (right).

The Estonia Geology Research crew examining specimens in the Institute of Geology collections (left); a typical museum drawer (right).

Much of our work involves finding specimens from our study locations and making quick and simple photographs for later reference.

Much of our work involves finding specimens from our study locations and making quick and simple photographs for later reference.

Again another scientific colleague we did not know before this trip helped us immensely and has become a friend. It is a remarkable universal fellowship. I hope we are able to return many such favors back in the United States.

Some fieldwork actually improved by rain

July 7th, 2009

UNDVA CLIFF, SAAREMAA, ESTONIA–I’ve never had anything good to say about rain during geological fieldwork, but our colleague Bill Ausich from Ohio State University insisted that it makes echinoderm fossils stand out better against the rock matrix. Turns out he’s right.

Two calices of the eucalpytocrinid crinoids at the Undva Cliff locality.  When wet the pure calcite of their skeletons contrasts brilliantly with the surrounding dark rock matrix.

Two beautiful calices of the eucalpytocrinid crinoids at the Undva Cliff locality on Saaremaa. When wet the pure calcite of their skeletons contrasts brilliantly with the surrounding dark rock matrix.

A Second Project Emerges on the Glorious Fourth of July

July 4th, 2009

KAUGATUMA, SAAREMAA, ESTONIA–It is always an important moment for a Wooster geology research team when it identifies its final student independent study project. Today Palmer Shonk found his. There is a remarkable exposure of a high-energy deposit in the Aigu Beds (Kaugatuma Stage, Upper Silurian) on the Sõrve Peninsula of southwestern Saaremaa island. These rocks have spectacular crinoid materials, including elaborate holdfasts, along with stromatoporoids, bryozoans and brachiopods. The sediments still retain their original dune bedding forms showing the high energy conditions under which they were deposited.

Palmer and Rob at the Kaugatuma locality.  I probably shouldn't point out again the spectacular weather.  That would be like bragging.

Palmer and Rob at the Kaugatuma locality (N58.12409°, E22.19375°). I probably shouldn't point out again the spectacular weather. That would be like bragging.

Crinoid fragments (left) and well-preserved stromatoporoids (right) at the Kaugatuma locality.

Crinoid fragments (left) and well-preserved stromatoporoids (right) at the Kaugatuma locality.

Palmer’s job will be to understand the original organisms and the environments in which they lived and died (a paleocommunity study) as well as the means by which the remains were redistributed and preserved (a taphonomy study). It is exciting material which will make an excellent project.

At the end of the day we said good-bye to our generous and thoughtful Estonian hosts Olev and Ingrid Vinn. We are on our own now in Estonia, but they’ve trained us well. They left us at the marvelous Kaali Meteorite Craters, estimated to be about 7500 years old.

The main Kalli meteorite crater.  On the far side of the pond you may see a spot of blue.  That is Rob McConnell performing his job as a scale very well.

The main Kaali meteorite crater. On the far side of the pond you may see a spot of blue. That is Rob McConnell performing his job as a scale very well.

« Prev - Next »