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.

Tiny bit of wildlife on Hiiumaa

July 1st, 2011

KÄINA, ESTONIA–This is a shout-out to our Wooster Geology colleagues currently working on the barren volcanic island of Iceland. We thought they might want a break from the bleak expanses of black basalt for a little color of wildlife from Estonia. The creature above, of course, is a grasshopper we found in our quarry today.

This colorful moth seems to specialize in the nectar of a common thistle here. It is a Six-Spot Burnet (Zygaena filipendulae).

A native bee on a daisy.

And delicious wild strawberries every day!

Quarry time on Hiiumaa

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!)

A second new Senior Independent Study project begins in Estonia

June 30th, 2011

KÄINA, ESTONIA–Today we moved our geological investigations from Saaremaa to the island to the north: Hiiumaa. Our friend Olev Vinn of Tartu University then led us to an abandoned quarry in the Hilliste Formation (Lower Silurian). This made Rachel Matt very happy as it is the place she has been studying as the potential site for her Senior Independent Study project. First, it is not filled with water; second, it is easy to get to; third and most important, it has a diverse mix of fossils and rocks crying out for her attention. She is shown above in front of what looks like an ancient mud mound.

The rocks and fossils are so good that the students quickly accumulated a pile of cool specimens. I had to stop them from picking up fossils because we’ve not even started to sort out the stratigraphy. A good sign!

Our friend Bill Ausich at Ohio State University will be pleased to hear that there is much crinoid debris, as shown here in this image. It is a calyx plate in the center, with stem fragments around it. Hiiumaa is the island on the Euro to the right of the top star.

There is much I can’t identify here, at least not immediately. Another good sign!

The only thing that I don’t like is that we’re on yet another island, and this one smaller than the last. So much water around so little land, and no way off except by these little ferries. Our car is the brown one in the front on the right. I’ll endure for science!

A few of the wildflowers on the alvars of Saaremaa Island, Estonia

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!

A little something for igneous petrologists

June 29th, 2011

Like a lonely little onion in a petunia patch, a boulder of red granite sits on the cobblestone beach off Soeginina Cliff, western Saaremaa, Estonia.

KURESSAARE, ESTONIA–Hard-rock geologists sometimes complain that I flood this blog with too many sedimentary rocks and fossils (and just wait until I get to the Estonian wildflowers!). There are actually quite a few igneous and metamorphic rocks on Estonia — just like there are in Ohio — in the Pleistocene glacial till. They show up well on the beaches here in contrast to the sedimentary rocks around them.

A closer view of the above rock, just to show it really is granite.

Granite in action! A granitic vein through some unfortunate rock.

Saaremaa Silurian stromatolites studied

June 29th, 2011

KURESSAARE, ESTONIA–Our fieldwork today at the Soeginina Cliff locality ended with an examination of a sequence of stromatolites near the top of the exposed Ludlow section. Stromatolites are layers of sediment accumulated by photosynthetic cyanobacteria. They are the earliest fossils known, some 3.5 billion years old, and these structures are still being formed today. Bacteria were present at the beginning and no doubt will be the only surviving life at the end.

In the image above, the stromatolitic portion of the outcrop begins at Nick’s upraised arm and goes almost to the top of the exposure. It is a complicated story because they seem to be sitting on an erosional surface cut into the dolomite underneath. There are also patches of what appears to be gravel under some of the stromatolite domes. A dolomitic sand fills the spaces between the stromatolite heads. Stromatolites can tell us a lot about the paleoenvironment of this area during the Silurian.

Closer view of the stromatolites at Soeginina Cliff.

Top view of the Soeginina stromatolites showing the fine layering produced by cyanobacteria. (Note the clever use for scale of a Euro with the map of Estonia on it. You can easily pick out the island of Saaremaa!)

I don’t usually come across stromatolites in my work. The last time I saw a few was with Matthew James on a great field trip to British Columbia. Part of the joy of supervising student research is that I must learn alongside them!

Thriving in the shingle: the story of Sea Kale

June 29th, 2011

KURESSAARE, ESTONIA–A very common perennial plant at the foot of the cliffs we are studying in Estonia is Sea Kale (Crambe maritima Linnaeus). It is beautiful with large, thick leaves and central stalks with bursts of white flowers, each with a purplish throat and yellow pistil. Turns out there is a bit of geological context and history of this edible plant in Western Europe.

Sea kale lives in a place where few other plants can survive. Shingle and cobblestone beaches have very little soil and are usually saturated at depth with brackish water from rain mixed with seawater. If the cobbles are mostly calcareous, as they are on Saaremaa, nutrient levels are low. Sea kale does well in this place because it is halophytic (tolerant of higher salinity than most terrestrial plants) and can collect enough nutrients because it has so few competitors. Its seeds float and so the plant can disperse via coastal sea currents. It is pollinated by numerous species of flies, beetles and bees, so it has no dependence on a particular pollen vector.

Sea kale was a popular vegetable in Europe during the 19th Century and before, but it fell out of favor as more easily cultivated plants became marketable. The new geological angle on sea kale is its ability to grow nutritious tissues in salty water. As freshwater resources become more scarce, biologists are looking at more ways to cultivate sea kale in marginal marine environments, and geologists are helping identify and preserve limestone shingle and cobble beaches for its continued growth. One of those places is Vilsandi National Park in western Saaremaa where we’ve been working this week.

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