Stratigraphy and paleoenvironment of the Soeginina Beds (Paadla Formation, Lower Ludlow, Upper Silurian) on Saaremaa Island, Estonia — An abstract submitted to the Geological Society of America for the 2012 annual meeting

July 19th, 2012

Editor’s note: The Wooster Geologists in Estonia this summer wrote abstracts for posters at the Geological Society of America Annual Meeting in Charlotte, North Carolina, this November. The following is from student guest blogger Richa Ekka in the format required for GSA abstracts:

Stratigraphy and paleoenvironment of the Soeginina Beds (Paadla Formation, Lower Ludlow, Upper Silurian) on Saaremaa Island, Estonia

EKKA, Richa N., WILSON, Mark A., NOVEK, Jonah M., Department of Geology, The College of Wooster, Wooster, OH 44691 USA; VINN, Olev, Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia

The Soeginina Beds in the Paadla Formation on the island of Saaremaa, western Estonia, are a Lower Ludlow (Upper Silurian) sequence of dolostones, marls, and stromatolites. They represent rocks just above the Wenlock/Ludlow boundary, which is distinguished by a major disconformity that can be correlated to a regional regression on the paleocontinent of Baltica. We interpret the depositional environment of the Soeginina Beds as having been a hypersaline lagoon. Our evidence includes halite crystal molds, oscillation ripples, eurypterid fragments, stromatolites, ostracods, gastropods, Chondrites trace fossils, intraclasts and oncoids. Nautiloid conchs are common, probably because storm currents washed them in. We measured two sections of the Soeginina Beds at Kübassaare, eastern Saaremaa, western Estonia. The beds in one section are virtually horizontal; in the second they are steeply dipping, probably because of Pleistocene glacial ice overpressure. The beds begin with fine-grained dolostone and end with large, well-preserved domical stromatolites. The equivalent section at Soeginina Pank in western Saaremaa (about 86 kilometers away) has larger oncoids, branching coral fragments, and smaller stromatolites. It is also more heavily dolomitized. We interpret these differences as showing the western Soeginina Beds were deposited in slightly deeper, less saline waters than those in the east at Kübassaare.

Our last evening in Estonia

July 17th, 2012

TALLINN, ESTONIA–We had our final group dinner in the Olde Hansa restaurant. (Freezing at an outside table, I might add, but the food and company was excellent.) We leave for the USA at 5:00 a.m. tomorrow morning. Pictured above, just after our hearty dinner, are, from the left, Mark Peter, Jeff Thompson, Alyssa Bancroft, Mark Wilson, Jonah Novek, Bill Ausich, and Richa Ekka. It is a delightful team. We are already looking forward to our Ohio reunion.

Bill’s image of our last dinner in Tallinn. So much fun, especially after such a successful field trip. Note that it was a bit chilly!

Some wildflowers from the western islands of Estonia

July 17th, 2012

TALLINN, ESTONIA–This is a tradition on my field trips: a sampling of flowers we’ve seen. We are so fortunate to be working in such a beautiful place. It would be a pity not to share. I don’t have any identifications, so feel free to add them in the comments. [The above flower is Campanula persicifolia.]

(Actually I do know that this is a thistle and a Six-Spotted Burnet moth.)

This wild rose has raindrops from the first downpour we experienced at Undva Pank.

This geranium-like flower is one of the most common on Saaremaa.

This is the first time I’ve seen these little red stars.

These long yellow shoots were found only on the alvars on the Sarve Peninsula on Hiiumaa.

These look a bit like Mountain Laurel at home.

I have no idea what these lily-like flowers are. They are striking in the field.

A museum visit: Institute of Geology at Tallinn University of Technology

July 17th, 2012

TALLINN, ESTONIA–This morning Bill Ausich and I examined fossils in the collections of the Institute of Geology at Tallinn University of Technology (the cool exterior of which is shown above). The Chief Curator, Ursula Toom, generously came in from her vacation to show us some important Ordovician and Silurian crinoid specimens, as well as assemblages from the Lower Silurian throughout Estonia. We had an excellent time looking at gorgeous fossils in a classic museum. (We were here in 2009 with Rob McConnell and Palmer Shonk as well.)

It must be an interesting place if they bolt a rock up off the ground in front!

Bill is here looking at crinoids Ursula set aside for us to examine. Note his use of an iPad for taking notes and images, just like Wooster geologists did last year at Ohio State. Bill carries his entire pdf library with him on his iPad, and makes many annotated images of museum specimens.

Typical hall of cabinets in the Institute of Geology. Each set of drawers is on a mechanical device for closing the aisles to increase storage space.

This is a row of cabinets with one drawer opened. Note the use of a drawer partially opened underneath for support. (A rough experience once before I learned this trick …)

A typical drawer of specimens. These are newly collected from the Reinu Quarry by our friend and colleague Olev Vinn.

A specimen label. Unfortunately some are nearly indecipherable. Sometimes it is because a Russian worker was transliterating information into Latin letters. There is often an interesting mix between the Russian, Estonian and English languages. Fortunately Ursula and others can quickly translate for us!

We enjoyed working in the Institute of Geology collections very much. They are not only superbly organized, much of their content is listed (and even imaged) online. We saw many critical specimens, and Bill was able to borrow some important crinoids. Thank you to Ursula for her kindness and excellent assistance!

 

Goodbye Hiiumaa, Hello Tallinn!

July 16th, 2012

TALLINN, ESTONIA–Early this morning the Wooster/OSU geologists left the Estonian island of Hiiumaa on the ferry from the port of Heltermaa (58° 52′ N, 23° 3′ E; seen above). After a 90-minute ferry ride, we landed on the Estonian mainland. We looked briefly at some quarries near Pusku south of Haapsalu (the limestones were too dolomitized for our liking) and then made the two-hour drive to Tallinn. After negotiating the most miserable intersection in Europe (which is under perpetual construction), we at last gassed up our cars and turned them in to the Sixt rental agency. There is nothing quite like the feeling of returning vehicles safely after such a long trip — it is only topped by returning students safely to their homes, of course! We are now in Tallinn for two nights. Bill and I have an appointment with the chief curator at the Institute of Geology in Tallinn as our students take a day off in the city. We are all staying at the St. Barbara Hotel near Old Town — a place beloved by many past Wooster students (depending on whether we have drunk Russians serenading us from the street all night.) I like that the building stone is a beautiful local Ordovician limestone.

The coiled-and-ribbed fossil mystery deepens on Hiiumaa

July 15th, 2012

KÄINA, ESTONIA–It has been a rainy day on the Estonian island of Hiiumaa. The Wooster geologists stayed inside most of the day to work on their Geological Society of America abstracts. Bill Ausich and his Ohio State University team, though, returned to the Hilliste Quarry and continued to collect fossils. To our great surprise, they picked up two more specimens of that strange planispirally-coiled shell that Richa found on July 13. One is shown above, and the “venter” view is shown below. All specimens were found in a yellowish unit that matches the matrix in the fossils (although we’ll check in the lab to make certain). These new finds reduce the chances that the fossils are a product of “site contamination” in which a visitor discards specimens from a previous trip, often to make room for new ones. That is still a possibility, but an increasingly remote one.

So what are these? They look very much like Mesozoic ammonites, all the way down to deflections of ribs along the periphery as you might be able to see above. (Specimen photography in a hotel room has its challenges.) The earliest ammonoids, the larger group that contains ammonites, appear in the Devonian (the period after the Silurian), so it is unlikely we are looking at that group. They are certainly mollusks, though, so most likely gastropods (snails) or nautiloids. Coincidentally enough, Wooster alumnus James St. John has a webpage with a photograph of a coiled, ribbed nautiloid known as Graftonoceras, which you will note has many similarities with our mystery critter. The specimen he photographed is in the museum at, of all places, Ohio State!

The last holdouts of pagan Europe

July 14th, 2012

KÄINA, ESTONIA–The little island of Muhu between Saaremaa and the Estonian mainland, had a large prehistoric population — much larger than it has today. The Muhu Estonians built a large fort of stone heaps near the western coast opposite Saaremaa so that they could control the traffic and trade through the Small Strait. The remains of that fortification are seen above. In January 1227, Teutonic Crusaders cornered the last of the pagan Estonians in this stronghold. (They were, in fact, among the last pagans in all of Europe.) Reports say that 20,000 soldiers besieged 2500 Estonian warriors for six days here. All the Estonians were killed save one, who escaped by pretending to be a victorious crusader. Most of the stones of the fort were removed to build the causeway between Muhu and Saaremaa, but the site remains as a ring of earthen walls and a stone monument (below) marking the bloody battlefield.

Wooster geologists return to Saaremaa and Muhu one last time

July 14th, 2012

KÄINA, ESTONIA–Today the Wooster/OSU team crossed the strait between Hiiumaa and Saaremaa to visit some earlier sites one last time on this trip. The Ohio State paleontologists stayed on the northern part of Saaremaa to look for crinoids and Panga, Ninase and Undva Cliffs; the Wooster geologists went farther south and west to visit Soeginina Pank (above) and Nick Fedorchuk’s 2011 field area. This was important to us so that we could compare observations here to Richa Ekka’s exposure of these beds on the eastern side of the island.

Richa stands by Nick’s Soeginina locality to compare it to her own rocks. This Soeginina section seems considerably more dolomitized in the west than the east.

Jonah and Richa at Nick’s outcrop. Richa is pointing to the Wenlock/Ludlow boundary horizon, and Jonah is showing the stromatolite layer near the top of the section. Richa’s section in the east begins somewhere above her finger.

We were impressed by how poorly preserved the stromatolites are in Nick’s section compared to the gorgeous specimens Richa studied earlier this week. You can barely make out the laminae in this western sample. Look here at its equivalent in the east.

Another difference we noted between the Richa and Nick sections was that Nick’s has thin coral branches (above) in storm layers whereas Richa’s does not. Nick’s oncoids are also larger and more complex.

The amount of damage the Soeginina Pank outcrop received in the last year is astonishing. I had worried about our hammer blows leaving noticeable marks on the rocks. The freshly fallen blocks on the cliff above appeared since our visit last June. Much of this is likely due to ice floes slamming into the rocks during the winter.

After our observations at Soeginina Pank, the Wooster geologists drove to Muhu to visit an historical site (more later on that), then went north through Orissaare to Triigi where we reunited with our OSU companions and boarded the ferry for the ride back to our hotel on Hiiumaa. Our two matching field vehicles are seen above at the front of the ferry. We weren’t going to miss the last ferry to the island!

Quarry work continues on Hiiumaa

July 13th, 2012

KÄINA, ESTONIA–It was a beautiful Baltic day in the Hilliste Quarry on Hiiumaa. Thunderstorms swept by us to the east, but we stayed dry and enjoyed the quickly-changing cloudscape. The Wooster/OSU team was again studying the Hilliste Formation for both its crinoid content and general paleoecology. We did very well.

The typical limestone in the quarry is a biosparite/grainstone as seen above. The most common grains are bits of crinoid stems. The OSU team has found a few crinoid calices and calyx parts, but not as many as you would think given the enormous amount of crinoid skeletal debris in the unit.

It looks like a theme of this year’s Wooster study in the Hilliste Formation may be the sclerobiont (hard substrate-dwelling) fauna, especially the encrusters on corals, stromatoporoids and crinoid stems. Above you see an auloporid coral (the larger tubes connected at their bases) encrusting a favositid coral. Our other encrusters include crinoid holdfasts (three varieties), cornulitids (a kind of worm tube), sheet-like bryozoans, runner-like bryozoans (corynotrypids), and erect bryozoan holdfasts. As far as I know, no one has described a Rhuddanian sclerobiont fauna before.

We have our share of mysteries. Richa picked up the above coiled shell this morning. Bill and I have not seen anything like it in the Silurian before. If these were Jurassic rocks we would have called it a partial ammonite. We know it is not, but we don’t know what it is. A gastropod like Poleumita discors? A nautiloid cephalopod similar to Bickmorites? We’ll have to figure it out later in the lab.

Here is Jonah on the north quarry wall. We dress him brightly every day so we don’t lose him in the Estonian woods.

Richa is in her own world in the western part of the quarry looking for more paleontological treasures.

And finally, our Estonian animal of the day: a spider dutifully guarding her eggs in the quarry floor rubble. I suspect this is the Robust Crab Spider: Xysticus robustus (Hahn, 1832).
 

 

Exploring the Estonian island of Hiiumaa

July 12th, 2012

KÄINA, ESTONIA–The Wooster/OSU geology team took a break today from our usual field routine. We spent the morning consolidating notes and specimens (yes, that means the students slept very late) and then the afternoon seeing some of the major Hiiumaa sites. The highlight was visiting Hiiumaa’s iconic attraction, the Kõpu Lighthouse on the Ristna Cape. It is the oldest lighthouse in the Baltic states and reported to be the third oldest continuously-operated lighthouse in the world. It was completed in 1531 and has been working ever since. The Hanseatic League demanded a lighthouse here beside the most important trade route in the Baltic Sea. The original light was a fire that required 1000 cords of firewood every year, nearly deforesting the surrounding peninsula. The Germans bombed it in 1941, but only damaged its optical structures on top. It was an important navigational aid until 1997 when it was replaced by a modern radar system.

A model of the medieval version of the Kõpu lighthouse in the Tallinn Maritime Museum. Access to the top platform was by a long ladder. The light was a bonfire of pine wood.

The lighthouse staircase is incredibly narrow and steep, being cut into the structure in the 19th century. (Prior to this there was a wooden staircase on the outside.) Richa is better built for such a place than me!

Richa and Jonah wanted an answer to the famous “O-H-I-O” pantomime our OSU friends like to construct, so they made a C-O-W version. The lighthouse window here at the top is the “O”, you see. Maybe it will catch on. Maybe …

Near the end of the afternoon we visited the Ristna Lighhouse and one of the westernmost points on the island. (This is where Alyssa found her famous trilobite.) Richa and Jonah noted that large igneous boulders make excellent posing platforms at the edge of the sea.

As a brief nature vignette, here is a dung beetle (Geotrupes stercorosus) we saw deep in the Estonian woods at our lunch spot. I’m sparing you the dung itself!

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