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.

The painful history of the Sõrve Peninsula, Saaremaa, Estonia

July 6th, 2011

KURESSAARE, ESTONIA–This country has had the historical misfortune to lie between the Russians to the east and the Germans to the west with all their imperial ambitions in the last few centuries. The terrain is deeply glaciated and thus has few natural defenses beyond thick forests, extensive bogs, and rocky coastlines. It has been occupied by Crusaders, Swedes and Polish-Lithuanians besides the multiple incursions of Germans and Russians. The 20th Century has been especially painful for Estonians.

Yesterday the Wooster Geology Estonia team worked near Kaugatuma on the proximal end of the Sõrve Peninsula on the southwestern tip of Saaremaa Island (see the images above). We then traveled south down the full length of the peninsula to Sääre. We visited a small, eccentric military museum and learned much about the history of this region. I think this strip of land is emblematic of the recent historical travails of Estonians — and thousands of Russians and Germans as well.

This is a panoramic image looking from the top of an old Russian gun emplacement looking south to the end of the Sõrve Peninsula at the village of Sääre. For a larger view of this panorama, please visit the Sõrve Peninsula Wikipedia page. This peninsula, by the way, has only been connected to Saaremaa for about 2500 years. It and the other eastern Baltic islands are still rising from the sea as a consequence of post-glacial isostatic rebound.

On the left Rachel and Nick explore a massive concrete gun emplacement near Sääre. These were built by Imperial Russians to house the 12-inch guns shown on the right in a museum image. These guns commanded the western entrance to the Gulf of Riga. They were captured by the German Army in October 1917. Note that this was a World War I battle.

The Soviets occupied and annexed Estonia in 1940 following the secret protocols of the earlier Molotov-Ribbentrop Pact. Nazi Germany declared war on the Soviet Union in June 1941, and in October turned its attention to conquering the Baltic islands. In November 1944, the Soviets returned and re-invaded Estonia and its islands. Some of the fiercest fighting took place in the Sõrve Peninsula in both invasions, as can be seen in the above maps photographed at the Kuressaare Castle Museum of Saaremaa. Note the November 1944 Russian amphibious landing at Kaugatuma. You can see why the Sõrve Peninsula has a significant number of landmines still remaining in the undeveloped forests. (Since 1999 there have been at least 77 casualties from landmines and unexploded ordnance in Estonia.)

A Soviet artillery observation post (from the 315th Coast Guard Battery) disguised as a windmill. A nearby gun emplacement was connected to it through an underground bunker. The complex was captured by the Germans in the 1941 invasion. At the time, of course, there were far fewer trees.

Foxholes dug by defending German troops on top of Kaugatuma Cliff in November 1944. As you can see from the map above, the Soviet amphibious landing was successful. On November 24th, against a direct order from Adolf Hitler, the Germans evacuated the Sõrve Peninsula and thus the last part of Estonia they held. The Soviets reported that up to 7000 German soldiers had been killed on Saaremaa, Hiiumaa, and Muhu islands during their offensive.

Nick holds the rusted remains of a World War II artillery shell found near Sääre.

The museum we visited was filled with objects collected from the World War I and World War II battlefields on the Sõrve Peninsula. This shelf of bullet-riddled German helmets was particularly poignant. There was a similar shelf of Soviet helmets.

This is the text of a monument we found in the woods on the way to Sääre. It is the only such memorial I’ve seen here in all three languages of the combatants. (I could not find a way of editing out my own ghostly reflection.)

Without the old trenches, bunkers and decaying concrete fortifications, it would be hard to believe such violent events happened on these quiet islands. The occupations by the Nazis and Soviets had their own much more ghastly horrors as well, including mass executions, deportations and concentration camps. It is over now, though, and we can freely wander these beautiful shores and absorb ourselves in the arcane details of Silurian paleoecology while enjoying the flowers, butterflies and very friendly Estonian people. Here’s to peace and the vigilance to maintain it.

Return to a Silurian crinoid forest

July 5th, 2011

KURESSAARE, ESTONIA–Today our Wooster Geology team visited a favorite outcrop of mine: the Äigu Beds of the Kaugatuma Formation exposed on the northwestern shore of the Sõrve Peninsula on Saaremaa. These are Late Silurian (Pridoli) limestones with a great abundance of crinoid fragments — so many that they are locally called “ringstones” (see the above image of a crinoid stem and isolated ring-like columnals). Palmer Shonk (’10) studied this outcrop for his Independent Study thesis. We returned here today to collect more field data so that Palmer, Olev Vinn, Bill Ausich and I can write a professional paper on the depositional system and paleoecology.

The limestones show significant storm beds made of skeletal debris, especially the crinoids but also corals, stromatoporoids, bryozoans, brachiopods and trilobites. The most remarkable aspect of this exposure is the presence of an in situ crinoid “forest” of holdfasts (the part of the crinoid that holds it to the sediment). Our job today was to find out more about the non-crinoid fauna since Palmer and I have already mapped out the crinoid holdfasts. We hope to soon publish a rare look at a Silurian crinoid community essentially preserved in place.

The Kaugatuma outcrop on the Sõrve Peninsula of Saaremaa. This was a Russian amphibious landing zone in 1944. You can bet you’ll read more about that story later!

The star-shaped fossil with the hole in the center is a crinoid holdfast in place at Kaugatuma. There are dozens of these scattered across the outcrop. The crinoid is Enallocrinus. The hole in the center is the hollow lumen of the crinoid stem.

Nick found this calyx of another crinoid known as Eucalyptocrinites. Such well preserved calices are rare.

Nick also found this very nice trilobite pygidium (tail piece). It is preserved well enough that we can probably later identify it to the genus level.

Back to the Big Island for the Fourth of July

July 4th, 2011

KURESSAARE, SAAREMAA, ESTONIA–The Wooster Geologists Estonia Team today braved the Baltic Sea again and took a ferry from the island of Hiiumaa to return to their previous field sites on the island of Saaremaa. We worked at Soeginina Cliff on the western coast (shown above) to finish up Nick Fedorchuk’s Independent Study field research on the Wenlock-Ludlow (Silurian) erosional sequence. It was a fun day because we now have hypotheses to test about these rocks and fossils. More on those later.

The above rock shows an advantage we have studying exposures on rocky coastlines. The waves erode blocks of limestone from the cliff and polish them up on the boulder-strewn beach. We can thus see our rocks in three dimensions rather than just the flat cross-section we would normally have. The trick, though, is to know from where in the section the boulders were derived!

We found some excellent sections through the numerous oncoids in our outcrops as well. We saw that many are formed around gastropod (snail) shells — very much like a Jurassic version I recently described as one of Wooster’s Fossils of the Week.

Tonight we will celebrate the 4th of July with a pizza dinner in downtown Kuressaare. It is as close to American food as we can get here. On this holiday we salute the Wooster Geologists Iceland Team also far from home on the front lines of science!

Saying goodbye to the little island of Hiiumaa

July 3rd, 2011

KÄINA, ESTONIA–Today we had our last visit to our Silurian quarry working site (where I photographed the Paleofavosites coral fossil above, which by the way was preserved upside-down in the sequence), and then we had lunch in the town of Kärdla overlooking the Baltic. Tomorrow we take the early morning ferry back to the larger island of Saaremaa where we resume fieldwork. Here are a few last photographs from Hiiumaa.

The other Silurian outcrop on the island: Kallaste Cliff. A bit overgrown, we think.

Some purple flowers found in the woods near our field site.

Yellow flowers in the quarry itself. I do know the one on the left is a daisy!

Whitish flowers and then a moth-covered thistle. I photographed this Six-Spot Burnet moth earlier, but three on one flower deserved another image. I'm sparing you the photos of them mating!

Our hotel on Hiiumaa. For most nights we were the only ones there. The students said it reminded them of "The Shining".

A walk to the sea after lunch in Kärdla. We have enjoyed this weather very much.

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