I could not believe it! The very first site on the next day, Kaugatuma cliff, at the southwest, long stick-out of the Saaremaa island, was just as full of fossils as Ninase! Apparently, this was one of the most fossiliferous localities of the Silurian period.
At the time of this formation, the Caledonian mountains had formed, by the three-front collision between western Scandinavia, northern Greenland, and the British Isles. This massive clash closed up some shallow marine environments in the vicinity, and there is a visible transition toward more terrestrial (land) conditions. However, this is not seen here, in Kaugatuma cliff, which contains some of the last marine communities in this place.
The shore was teeming with exquisitely preserved fossils, completely dominated by crinoids, which very much look like aquatic plants, but actually are animals. They are related to starfish and sea urchins, all belonging to the echinoderm group, united by a five-sided or pentagonal symmetry: crinoids have five tentacly projections around its main body, starfish have five arms, and sea urchins’ mouths are divided into five parts.
What is mostly preserved from the crinoids here, however, is their long stalk, which in some forms here were unusually large. If they are large and abundant, they must have been doing very well in this environment.
The above picture was taken in place; the four below are front and back of two rock pieces completely stuffed with crinoid fragments I found and brought back home.
Here is another nice fossil. Luckily, it was not stuck in the ground as most other similar specimens, so I could add it to my collection.
This is a section of a crinoid stalk, preserved in three dimensions, with the clear calcite rings it is made up of. Below is a specimen that is just a fragment of the outer part of the stalk. I am not sure of what would have been inside when this animal was alive, but it probably was slimy.
There were many fragments that had small, round holes. This is where the “roots”, which were used to anchor the long, slender creature into the seabed.
Among this crinoid jungle, we found corals, brachiopods, sponges, gastropods and even some trilobites. Professor Graham Budd had announced a competition: the best trilobite find would be rewarded with a free drink on the ferry back home. So most of us were searching vigorously for trilobites. Personally, I thought finding a trilobite would be a most awesome reward in itself, and I think many others agreed.
Brachiopods can of course rival trilobites in sheer beauty, but they could basically be found in every second rock you looked at or flipped over, so they were not quite as thrilling to search for. However, I miraculously found this:
And what was even more miraculous was that I did not lose it in my pocket later! I have to keep it safe, for any bird or rodent might easily take it for a seed.
No, but seriously, it is a truly wonderful specimen, by my standards, and definitely one of my favourites. I think it is a rhynchonelliform, or articulate brachiopod, based on its shape, but I guess one must crack the shell open to find out for sure. (I’m not going to do that!) Articulate brachiopods have teeth holding their two shells together, rather than muscles, in contrast to the craniiformeans, or inarticulate brachiopods, which rely on a complex set of muscles to keep the shells closed. Muscles require more energy to be sustained, so the rhynconelliformeans had an edge over the craniiform brachiopods.
It was a very chilly morning, and my hands were aching from the cold, so there was at least something positive when we left for the bus to take us further on.
Next, we arrived at another shore (surprise!), also with abundant fossils (yay!!). This was the Ohesaare cliff, a famous late Silurian fish locality, so there was some hope of maybe finding a vertebrate fossil. (One of our teachers, Lars Holmer, did find a fish scale fossil, but I never got the opportunity to see it, so I have no idea of what it looked like.)
Lamentably, we were supposed to do some serious exercise to really examine the exposed layer sequence. In the previous locality, there were no cliff exposures to examine, just a flat carpet of fossiliferous rocks. Here, however, we would not be able to avoid some rock work.
There were fossil embedded in the exposed cliff rocks (can you find some on the picture below? look carefully, it’s not as clear as before), not just on the loose pebbles on the shore.
But, the purpose here was to do a so-called log of the exposure. This basically meant a proper scale drawing of the different sections we could see.
Luckily, the exposure was roughly evenly divided into four clear units, each around 50 cm thick, making the scale drawing easy on a lined paper.
Identifying the rocks in the layer, however, was a different story. The top section was dry, quite light grey to yellow limestone (investigated by an excited Aodhán with a bottle of hydrochloric acid, which fizzles if poured upon a calcium carbonate rock such as limestone); below was some dark grey, wet, yucky mud, with some lighter rocks embedded; next we had a section with some mud similar to the above one, but a lot more solid, light grey rock, once again limestone, I think; the base consisted of partly mud, partly darker rock (maybe stained by the mud).
I am not sure what to believe, but since only the three lower parts contained mud, and to a lesser amount in the lower layers, and because these three layers were wet, I want to interpret the mud as all belonging to the layer second to the top – if the groundwater table lies at this level, it may very well be that it is responsible for washing mud down to the lower layers. This sort of explains why the bottom sections contain less mud, and why they are wet too. However, this must be a slow process, or one that has begun relatively recently, because, otherwise, one would expect a thicker layer of mud accumulating at the bottom. It is a bit tentative, but particles are usually washed down in the ground profile by percolating water – there is even a beautiful word for this: eluviation.
So, the logging was done relatively quick, and was mostly forgotten when a Illiam Jackson, a PhD-studen, came cheering over having found huge bivalves (clams) stuck in the second-to-top bed mud. The next moment most of us were combing the exposure for them. They were not easy to find, despite being the size of a chicken egg, because they were of the same colour as the mud, so we had only the shape to go for.
It seemed hopeless at first, mostly because I was not sure of what their exact shape was, and how to distinguish them from the normal rocks pointing out of the mud.
However, perseverance paid off eventually. I found a half one. Too muddy to put in my pocket, I had to wash it in the cold water and roll it up in a paper napkin. Not exactly a professional handling of the fossil, but it had to do.
And now I knew what too look for, and – guess what – found two more! Now I had a fine collection of enormous Silurian bivalves!
However, this find was bleak in comparison to another discovery: my very first trilobite!
I actually found this piece before the bivalves, but it looked so strange – somewhat like a trilobite, but still not really. I hoped it was a trilobite, but doubted it. Later, however, I asked professor Budd to look at it, and he said it might be a very weird-angled cross-section of a trilobite. “But it’s not a winner”, he added, and I knew it, but was not bothered. I had found my own trilobite, and that certainly made my whole day, and the trip would be a success, even if this would be my last find.
Well, it wasn’t. On the way back, my eyes came over some pretty awesome trace fossils, probably made by burrowing worms. Not as spectacular as the other fossils, but for being a trace fossil, or ichnofossil, it was rather impressive.
The final stop for the day was a bit of an anti-climax: a meteorite impact crater in Kaali. I tried to tell myself, and others, that it was nice for a change, but it was too sterile. Of course, you cannot expect much else from an impact crater, but in the light of the earlier localities, this was rather dull. Massive, but dull.
One impressive feature was the big blocks of rock that had been thrust up at an angle by the impact shockwaves.
Another interesting thing was the way the trunks of the trees growing on the crater ridge were curved. This is because the soil is slowly creeping down toward the centre, dragging the trees down, while the trees strive to grow upright, and therefore bend their stems so the crowns will face as much upward as possible, to reach the sunlight. The trees came after the crater had been formed, and so did the lake, of course.
It had truly been a day of miracles. Yet, more was to come!
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