Silurian limestone under our feet

July 6th, 2012

KURESSAARE, ESTONIA–The 2012 Wooster Estonia expedition had its first official time in the field this afternoon. Jonah, Richa and I traveled the short distance from Kuressaare to the historical Sõrve peninsula in the extreme southwest of Saaremaa. There we explored the Äigu Beds in the Kaugatuma Formation exposed along the peninsula’s northwest coast. I know this place well from several visits, and it was the site of Palmer Shonk’s Independent Study project. The limestone here is mostly a high-energy encrinite (a rock made almost entirely of crinoid fragments) with many elaborate crinoid root systems in place showing the arrangement of a “crinoid forest”. Pictured above is a limestone bedding plane with two primary axes of the roots  (holdfast) of the genus Enallocrinus. The interior sediment has eroded away so that you can see the holes where “rootlets” emerged to penetrate the surrounding sediment.

Richa and Jonah on the swampy northwest side of the peninsula with the Kaugatuma Cliff exposed in the background.

Our liberally-educated students are here examining the surface of a granitic boulder brought here from Sweden by the last glaciation and dropped as an erratic. Of course, it is not the igneous rock that excites them — it’s the multicolored  lichens on it!

This project is funded by a grant from the National Geographic Society and the Wengerd Fund of The College of Wooster. Tomorrow we will introduce you to the Ohio State University team members and more details about our work and goals. We are very grateful for this research opportunity. We are also very pleased with the spectacular weather. Sunny and 26°C today.

 

Wooster Geologists return to Estonia

July 6th, 2012

KURESSAARE, ESTONIA–It took longer than we expected, but three Wooster geologists and four colleagues from Ohio State University are finally on the island of Saaremaa and ready for our fieldwork in the Silurian limestones along the shores here and on the smaller island of Hiiumaa to the north. We had a missed connection which delayed us a day in Tallinn, and everywhere we went our reservations were difficult to find, but it has at last worked out. Above you see Richa Ekka and Jonah Novek, two Wooster seniors who will be studying the Silurian sections for their Independent Study theses. Behind them is Moon Sound between the Estonian mainland and Muhu Island as viewed from a car ferry. Richa and Jonah are part of a long tradition of Wooster students who have worked in Estonia, some of whom you can meet by clicking our Estonia tag to the right.

Now we’re off to buy some lunch and take advantage of the fantastic weather to see some rocks. Much more will follow!

The view from my hotel room of Kuressaare Castle. Nice, eh?

First Wooster student presentations: The Estonia team

October 9th, 2011

MINNEAPOLIS, MINNESOTA–The first Wooster students presented today at the Geological Society of America annual meeting. Above is Nick Fedorchuk who talked about his work in Estonia studying the Wenlock-Ludlow boundary on Saaremaa Island and its implication for Silurian stratigraphy and depositional environments in Baltica.

Rachel Matt (above) presented her work on the Lower Silurian fauna found in the Hilliste Formation on Hiiumaa Island, Estonia. These fossils are critical evidence for the recovery of marine communities following the end-Ordovician mass extinctions.

It was fun watching Nick and Rachel interact with geologists who stopped by to see their posters. Not only did they learn a great deal about the rocks and fossils they are studying, they could also see how they fit into larger questions about Silurian plate tectonics and evolution.

Two other Wooster students also showed posters today: Lindsey Bowman and Andrew Collins. Photos and profiles of their work will be posted later.

A Day in Tallinn, Estonia

July 10th, 2011

TALLINN, ESTONIA–Like our Wooster Geology colleagues in Iceland, we also have a nearly-final day in a city. Tallinn is the capital of Estonia, the medieval town square of which is shown above. We started here briefly at the airport, and will leave from the same place early  tomorrow morning. The only difference is that we have one more big city to go: Stockholm, Sweden.

Tallinn, or at least a significant settlement in this place, goes back to the 11th Century, and before that there are Bronze Age artifacts. After the Danes conquered it in the 13th Century, it became known as Reval until the Estonian War of Independence in 1918-1920 when the Estonians could finally give it their own name: Tallinn (or Tallinna). It was a member of the Hanseatic League, being an important trade link between northern Europe and Russia. (And so the merchants in the town square are dressed in the Medieval garb of “Old Hansa”.) This year it is a European Capital of Culture. Tallinn does not sit on a major river but takes advantage of Ordovician limestone heights to raise it above the coastal swamps and bogs.

We enjoyed a day off in the city under (as you might have predicted) sunny skies. Tomorrow is another travel day, and then back to work one more time in Stockholm!

The newly renovated Freedom Square in Tallinn. The memorial is for the Estonian War of Independence (1918-1920).

Rachel and Nick can be barely made out here on the other side of Freedom Square.

Suur Strait (Moon Sound, Moonzund)

July 9th, 2011

TALLINN, ESTONIA–The Wooster Geology team in Estonia successfully returned to the Estonian capital city of Tallinn today, which means we crossed by ferry the Suur Strait between the western Estonian islands (notably Muhu) and the Estonian mainland. This is an interesting strip of water with a complicated geological and human history.

There is an Estonian dream of building a bridge or digging a tunnel across the Suur Strait to eliminate the need for the ferry line and more efficiently connect Muhu and Saaremaa to the main part of Estonia. It will not be an easy task (and it is probably too expensive to ever be attempted), but it has led to considerable study of the strait and its oceanographic, biologic and geologic characteristics. The currents are complicated as they move between the Gulf of Riga to the south and the Baltic Sea proper in the north, and it freezes solid in the winter (when it is crossed by a 9 km long ice road). The strait hosts one of the most significant bird migration routes in northern Europe, and the marine fauna and flora here is still poorly surveyed.

The floor of the Suur Strait is highly variable from exposed Silurian limestone bedrock to thick mantles of glacial till. As you can deduce from the Google Earth image, some parts of the strait are very shallow, and the deepest regions are no more than 21 meters of water. Because of isostatic rebound, the region gets shallower about 2 mm per year as the land rises.

Suur Strait as viewed from northeastern Muhu (July 2007).

Historically, the Suur Strait has been the “backdoor” to the Gulf of Riga to the south. Any navy that controls the Baltic wants to keep that backdoor open for itself, but close it to enemies. This was especially the case during World War I when the Imperial German Navy sought to trap elements of the Imperial Russian Baltic Fleet in the Gulf on October 17, 1917, during Operation Albion. Most escaped north through the Suur Strait (known then in English as Moon Sound) following carefully dredged channels lined with mines. One Russian battleship, the Slava, was severely damaged and took on too much water to pass back through the shallow strait and was scuttled.

The Suur Strait was crossed by the Germans in 1941 as they invaded the western Estonian islands (Operation Beowulf), and again by the Russians when they re-invaded in 1944 (Moonzund Landing Operation).

We made it across on one of the car ferries which ply the Suur Strait between Kuivastu and Virtsu. Like the Russian warships of old, it also follows a dredged channel through the shallow and storied waters.

View from our ferry west across the Suur Strait towards Kuivastu on Muhu island. Last ferry ride of the trip!

Reference:

Saaremaa Fixed Link – Report of Preliminary Environmental Impact Assessment – Final Draft – 15.07.2005 (Google this and you can get a thorough report as a pdf.)

A visit to Kaali Crater for our last day on Saaremaa

July 8th, 2011

KURESSAARE, ESTONIA–A dramatic geological site on our last Saaremaa day: the meteorite craters at Kaali. We hiked around the largest crater (shown above) and then visited one of the smaller subsidiary craters nearby (shown below). The main Kaali crater is 110 meters in diameter and about 22 meters deep. The meteorite was between 20 to 80 metric tonnes and was traveling 10-20 km/s. It broke up into pieces 5-10 km above the ground before the multiple impacts. The date of this event is disputed. We have seen ranges in the literature from 4000 to 2700 years ago. Some archaeologists have evidence that an ecological catastrophe followed the impacts with massive wildfires and a drop in crop production for a century. Others think there is a connection between the Kaali event and Baltic mythology. (I think it is a delightful coincidence that the Estonian place name “Kaali” used for this fiery event is coincidentally the same name as the fearsome Hindu goddess.)

To our surprise, the Kaali Museum had a thorough display on the geology of Saaremaa, including this polished cross-section through Nick’s critical Wenlock/Ludlow section.

Our last stop was a virtually abandoned little harbor at Turja on the southeastern coast of the island. It was a nice place for lunch as we contemplated how our fieldwork did not include bears and wolverines (as with our Wooster colleagues in Alaska) or gale-force winds and thick fogs (as experienced by our Iceland friends). We were quite fortunate to gather such excellent geological data with so few such adventures!

Tomorrow we drive to Tallinn to spend a day and a half, and then to Stockholm for a day in the Natural History Museum looking at comparative Silurian material. On Wednesday of next week we fly home.

Paleoecology of the Hilliste Formation (Lower Silurian, Llandovery, Rhuddanian) Hiiumaa Island, Estonia: An example of a shallow marine recovery fauna — An abstract submitted to the Geological Society of America for the 2011 annual meeting

July 7th, 2011

KURESSAARE, ESTONIA–Editor’s note: The Wooster Geologists in Estonia found enough material, and had enough time, to write abstracts for posters at the Geological Society of America Annual Meeting in Minneapolis this October. The following is from student guest blogger Rachel Matt in the format required for GSA abstracts:

PALEOECOLOGY OF THE HILLISTE FORMATION (LOWER SILURIAN, LLANDOVERY, RHUDDANIAN) HIIUMAA ISLAND, ESTONIA: AN EXAMPLE OF A SHALLOW MARINE RECOVERY FAUNA

MATT, Rachel M., WILSON, Mark A., FEDORCHUK, Nicholas D., Dept of Geology, The College of Wooster, 944 College Mall, Wooster, OH 44691-2363, VINN, Olev, Dept of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia

The Hilliste Formation (Lower Silurian, Llandovery series and Rhuddanian stage) is well exposed in a quarry in western Estonia. During the deposition of this unit, Estonia was part of the paleocontinent Baltica, which was located near the equator. The Hilliste Formation thus records the recovery of tropical invertebrate marine communities following the mass extinction at the end of the Ordovician. Globally, pre-extinction levels of marine diversity were not met until the Wenlock, about 15 million years after the end of the Ordovician; this formation was deposited about three million years following the event. The Hilliste Formation contains a diverse fauna including brachiopods (orthids, atrypids, rhynchonellids, pentamerids, and strophomenids), corals (favositids, halysitids, heliolitids and rugosans), stromatoporoids, bryozoans, gastropods, crinoids, ostracodes and trilobites. We measured, described and sampled the Hilliste Formation at Hilliste Quarry on Hiiumaa Island, western Estonia. The unit records a regression from depths between normal and storm wavebase to depths at or above normal wavebase. The evidence for this paleoenvironmental interpretation includes more argillaceous beds in the bottom two-thirds of the formation and more biosparite/grainstone upwards. The top third of the formation consists of massive biosparite/grainstone with little clay and overturned and fragmented corals and stromatoporoids indicating high depositional energy. The fauna changes stratigraphically upwards from one dominated by brachiopods and gastropods to a community primarily of corals, stromatoporoids and crinoids. This fauna provides additional information about biotic recovery in eastern Baltica and its implications for the migration of Early Silurian Baltic taxa into other regions.

Stratigraphy and paleoecology at the Wenlock/Ludlow boundary on Saaremaa Island, Estonia — An abstract submitted to the Geological Society of America for the 2011 annual meeting

July 7th, 2011

KURESSAARE, ESTONIA–Editor’s note: The Wooster Geologists in Estonia found enough material, and had enough time, to write abstracts for posters at the Geological Society of America Annual Meeting in Minneapolis this October. The following is from student guest blogger Nick Fedorchuk in the format required for GSA abstracts:

STRATIGRAPHY AND PALEOECOLOGY AT THE WENLOCK/LUDLOW BOUNDARY ON SAAREMAA ISLAND, ESTONIA

FEDORCHUK, Nicholas D., WILSON, Mark A., MATT, Rachel M., Dept of Geology, The College of Wooster, 944 College Mall, Wooster, OH 44691-2363, VINN, Olev, Dept of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia

The boundary between the Wenlock Series and the Ludlow Series can be easily observed on the island of Saaremaa in western Estonia. Here, the boundary is distinguished by a major disconformity that can be correlated to a regional regression described in several previous studies. During this time, western Saaremaa was a lagoonal facies that reflected sea-level changes within the Baltic Basin. We measured and described this Wenlock-Ludlow boundary interval at Soeginina Cliff on the western shore of Saaremaa. Here this boundary consists of the Vesiku Beds of the Rootsiküla Formation (Wenlock) overlain by the Soeginina Beds of the Paadla Formation (Ludlow). The Vesiku Beds (Wenlock) record a carbonate lagoonal environment with finely laminated beds and Thalassinoides burrows (indicating oxygenated bottom conditions). The fauna is much less diverse than that in normal marine sediments of the Wenlock. The top surface of these beds (the primary discontinuity surface) shows a microtopography and dissolution consistent with exposure and abrasion. The top 20 centimeters also show diagenetic alteration of the laminated sediments, probably from fluids traveling through the Thalassinoides burrow systems. The Soeginina Beds (Ludlow) show pulsating transgressive sediments with multiple discontinuity surfaces. Large oncoids are common in these beds. They have distinctive shapes because they were initially spherical and later stabilized and grew like small stromatolites upwards. These forms may indicate periodic energy reductions in these transgressive waters. There are also storm beds with biogenic debris including oncoids nucleated on gastropods. This boundary interval is topped by thin dolomites and stromatolites. This example of the Wenlock-Ludlow boundary can be correlated with other such disconformities recorded in a variety of depositional environments, such as in the equivalent reef complexes of Gotland, Sweden.

Inside a secret Soviet missile base — 20 years later

July 7th, 2011

KURESSAARE, ESTONIA–When I was growing up the Soviet Union was simply an unchangeable fact of life. The United States had an implacable enemy, and we were locked in a struggle that would last my lifetime, at least. That lifetime was almost certainly going to be short, of course, because sooner or later someone would push the nuclear button and, in the words of the Kingston Trio, “… we will all be blown away”.

Thus it is very much an existential treat to have lived into my sixth decade and be able to walk through the remains of a secret Soviet missile base to get to the Suuriku Cliff locality this morning. The Evil Empire collapsed, the Baltic States were liberated, and massive overgrown concrete bunkers stand as evidence of a nearly unimaginable past only 20 years old. I am privileged as a geologist to be able to travel to such places and feel the turning points of history.

While constructing this Google Earth image of Tagalaht Bay to show the location of this Soviet base (one of dozens on the island, by the way), I saw something cool in the south: ancient shorelines. Saaremaa, like most of the Baltic region, is experiencing post-glacial isostatic rebound. The land is rising at least 2 mm per year (and in some places much more), so the sea is retreating. These shorelines are only a few thousand years old.

Wooster Geologists return to Suuriku Cliff, Saaremaa, Estonia

July 7th, 2011

KURESSAARE, ESTONIA–Today we visited one of Rob McConnell’s (’10)  Senior Independent Study field sites on the northwest coast of Saaremaa. Suuriku Cliff (N58.50875°, E21.99818°; see above image) is an exposure of the Jaani Formation (Lower Silurian, Wenlock). There are two members here: the upper Ninase (most of the cliff) and the lower Mustjala. Rob sorted out the paleoecology and environments of deposition of these two members using samples from this location and two others.

We were here today to find additional crinoid calices to continue a project Bill Ausich, Olev Vinn and I are pursuing. We found a few, too, although none very photogenic. It was also a chance for us to see more examples of Silurian limestone and fossils before we leave the island on Saturday.

Nick Fedorchuk and Rachel Matt at Suuriku Cliff. We want to show that some Saaremaa cliffs really are more than a meter high!

Panorama of Tagalaht Bay south of Suuriku Cliff near Veere. This bay is where German naval and infantry forces invaded Saaremaa on October 11, 1917, in Operation Albion.

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