Archaeopteryx and all that

Wednesday 8 November

After seeing all those wonderful fossils, the next day we learnt why so many had been so well-preserved in this small area. During the Upper Jurassic, 148 Ma, the arrangement of the continents was quite different from today and this area of Bavaria lay close to the Tethys Ocean, between Europe and Africa at 25 and 30 degrees latitude in a much warmer climate, probably in an area of lagoons containing salt water.

The excellent preservation of the fossils was due to their rapid burial in finely-grained limestone sediment undisturbed by predators or burrowing organisms. This indicated a rather hostile bottom environment with sudden storm surges producing a profusion of fine limestone fragments which rapidly buried any organisms unfortunate enough to be caught up in the storm. So everything that fell into the lake, including casualties of the storms from the surrounding land area and islands, was fairly rapidly covered by limestone. Strata only a few cm thick can be traced for many km. At Maxburg quarry, which we visited during the afternoon quarry we saw that several layers of "Flinzen" consisting mostly of limestone only a few mm thick were separated by "Faeule" layers which were thicker and more irregular and contained more clay and mud mixed with the limestone. The quite different texture of the "Faeule" is because they were terrestrial sediments entering the lagoons from the land, maybe as a result of violent storms.

Guenther pointing out the flinzen and faeule at the Maxburg quarry

We stood back and studied the layers, reflecting that most of the geological time represented by the sequence lay in the gaps between the layers, the long quiet periods without storms when no sediment was laid down. Although it looked to be a gentle process of sed imentation, catastrophism seemed to be the cause of the formation of the layers rather than gradualism.

We had our own chance to search for fossils in the Schernfeld quarry by splitting the limestone fragments lying around the quarry, so it was hammers and chisels to the fore. We found an abundance of fish coprolites and nearly everybody found a sample of Saccocoma tenellum (a crinoid) with which to weigh down their luggage. Andrea also found a specimen of Mecochirus longimanatus (a shrimp) and we were able to purchase other fossils of fish, shrimp and insects from the quarry workers. We also collected examples of dentrites that we found fascinating and very beautiful, so more weight for the rucksacks.

The magnificent dendrite flooring of the Langenaltheimer quarry

On our way to the next stop, we also passed a series of rock formations called, aptly, the Twelve Apostles. These are the remains of reefs formed by sponges and microbial mats during the Cretaceous when shallow seas covered the area. The softer rocks covered the area. The softer rocks between the reefs have eroded away to leave the Apostles standing as isolated white outcrops.

In the afternoon we visited the quarry at Maxburg and also the Langenaltheimer Haardt quarry, the site of four Archeopteryx finds. We saw the Turkish quarry workers sorting out the stones and very hard work it looked to be. Guenther took a broom and cleared the dust off a very fine example of dentrites on the floor of the quarry a few sq m in size so that the photographers could all rush in. Some of us would have liked to take this home to lay in the floor. It would become a very interesting talking point.

All in all a very busy two days. We saw a lot and learnt a lot and now have a much better understanding of the sedimentary processes at work during the closing stages of the Jurassic in Bavaria. I shall continue to look at the beautiful pictures that we have for a long time to come.

As a postscript, Neil and I called in at the Senckenberg Museum, Frankfurt, on our way back to the Netherlands. There we saw the 10^th Archeopteryx specimen that has recently been found. It is on display in the museum until it goes to America. We felt that we had become quite expert in recognising the dentrites and Saccocoma tenella on the same slab as the fossil so we were quite convinced that it was not a copy. The museum will be very sorry to see it go. It is now our aim to go "Archeopteryx spotting" in Berlin and Haarlem as well.

A beautiful fish pecimen in the Buergermeister-Mueller Museum, Solnhofen

Eileen A Lawley