Estonian Independent Study fieldwork completed!

July 7th, 2009

KURESSAARE, SAAREMAA, ESTONIA–Today in a cold drizzle we measured the last section and bagged the last sample for our field projects. Tomorrow we leave the beautiful island of Saaremaa and drive to Tallinn. The next day we will study fossils in the University of Tallinn collections to complete our survey of the Silurian communities preserved in this part of the Baltic.

Rob McConnell is sorting out the paleoecology and paleoenvironments of the upper Mustjala and lower Ninase Members of the Jaani Formation (Wenlock) at three sites on the northern coast of Saaremaa. He has some very cool stromatoporoids, corals and bryozoans which are sometimes complexly intergrown and are almost always bored with long, thin holes.

Wonderfully symmetrical and large stromatoporoid (a kind of fossil sponge) preserved in the Undva Cliff, northwestern Saaremaa coast.  The surrounding blue-gray sediment is a calcarous clay with other smaller fossils such as brachiopods and bryozoans.  The stromatoporoid itself is a community with endosymbiotic corals and worms.  (Mustjala Member, Jaani Formation, Wenlock).

Wonderfully symmetrical and large stromatoporoid (a kind of fossil sponge) preserved in the Undva Cliff, northwestern Saaremaa coast. The surrounding blue-gray sediment is a calcarous clay with other smaller fossils such as brachiopods and bryozoans. The stromatoporoid itself is a community with endosymbiotic corals and worms. (Mustjala Member, Jaani Formation, Wenlock).

Palmer Shonk has a single locality on the Sõrve Peninsula of southwestern Saaremaa with an extraordinary accumulation of crinoids in both growth positions (as extensive holdfasts) and as storm-tossed skeletal debris. These rocks and fossils are part of the Aigu Beds (Kaugatuma Stage, Pridoli). We think that there were low mounds of calcareous mud colonized by numerous species of crinoids, bryozoans and stromatoporoids which were occasionally swept by strong currents and buried in coarse sand and gravel made almost entirely of crinoid bits. Palmer will work out the ecological structure of those original communities and then the environmental history which led to these thick storm deposits.

Crinoid holdfast seen sideways in the Aigu Beds, Kaugatuma Stage, Pridoli.  This structure is like the tap root of a tree.  It penetrated the sediment, tapering downwards, and produced lateral branches (radices) which held the crinoid in place in a relatively energetic marine environment.  Unlike a tree root system, this crinoid holdfast did not take up nutrients for the organism.  Crinoids are animals which filter the seawater for food with a head and arms at the opposite end of the stalk.

Crinoid holdfast seen sideways in the Aigu Beds, Kaugatuma Stage, Pridoli. This structure is like the tap root of a tree. It penetrated the sediment, tapering downwards, and produced lateral branches (radices) which held the crinoid in place in a relatively energetic marine environment. Unlike a tree root system, this crinoid holdfast did not take up nutrients for the organism. Crinoids are animals which filter the seawater for food with a head and arms at the opposite end of the stalk.

The Wooster 2009 Estonia Geological Research Team.  Photograph kindly taken by our colleague Bill Ausich.

The Wooster 2009 Estonia Geological Research Team. Photograph kindly taken by our colleague Bill Ausich.

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