Mark Wilson 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.
Mark Wilson 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.
Mark Wilson 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!
Mark Wilson 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.
Mark Wilson July 1st, 2011
KÄINA, ESTONIA–Rachel, Nick and I worked today in our lonely quarry on Hiiumaa measuring and describing this section of Lower Silurian (Llandovery, Rhuddanian) rocks and fossils. This is the fieldwork for Rachel’s Senior Independent Study.
One of the dilemmas is the nature of the lower interbedded limestones and shales. In places they show gently sloping beds and curved tops as here. Does this indicate some sort of mud mound or bioherm? Or is it a function of slumping in the quarry itself? (I'm leaning toward the latter.)
The fossils here are excellent, including corals and bryozoans. (Just because I could I expanded the image of the mite!)
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.