Real Geology

Munich lies on the banks of the river Isar and the celtic meaning of the name is 'Raging Torrent.' Towards the end of the 19th century, a canal was built parallel to the river and the river banks were steepened and reinforced to reduce the risk of flooding in Munich, particularly during the alpine-snow melting period in the spring and early summer. Now, at the change of the 20th to 21st centuries, this work is being reversed, the old embankment reinforcements are being removed and the river banks restored to their original, gentle sloping shape, reviving the natural character of the river. In order to give these new embankments a chance to settle, they in turn have been reinforced with slabs and boulders of an interesting limestone, interesting because some of the slabs and boulders are rich in calcite crystals or fossils. I have never detected these two together in any piece of stone and the most common condition is that the stone contains neither.

Whenever a new shipment of slabs and boulders is delivered, any hobby geologists around, descend on it and reduce the lot to mere fragments and dust, if it contains either crystals or fossils. I witnessed the delivery of a new shipment at the beginning of April, when I was alone, being walked by the dog next to the river; this meant no competion. Unfortunately, the load was dumped by the truck in the middle of a vast expanse of deep mud, churned-up by the bulldozer working the embankment. I was forced to build a 'causeway' from dry land to the pile to keep my feet dry, this worked admirably on the way to the pile, which of course, turned out to be completely sterile but was less effective on the way back. One of the stepping-stones tilted and deposited me, on my back, in some 10 cm of Isar mud.

At that time, S260 was dealing with crystal structures and symmetry. I recall lying in the mud and being concerned about disturbing the symmetry that the mud formed, in a line around my head, around my shoulders, arms and legs, perfectly dividing a clean and dry front from a very dirty, wet back. The water temperature was around 4-5° C and the air temperature only some

9-10° C, so the symmetry had to be sacrificed in order to get up and get home, about 20 mins walking-time away! I may have been alone when crossing to the rocks, on the way back, however, there was a considerable audience, all delighted with my performance and with the reaction of the dog who was looking-on in a most disapproving manner. The walk home was miserable and uncomfortable to say the least and the reception when I got there decidedly more 'kuhl' than 'cool', but I did manage to stop the traffic on the way, something which I have never previously achieved.

The following day, I witnessed another new delivery, I was alone again and this time, the conditions were more favourable. Despite further disapproving looks from the dog, I searched the pile, which proved to be very rich in fossils, mainly ammonites and other mollusca/brachiopoda. Since most of these were contained in giant slabs of stone, I thought that I was going to be frustrated yet again, however, I eventually found a piece of stone, about 1 kg in weight, containing a good, if incomplete relief of an ammonite. On my way home, I checked with the lorry driver and the landscape engineer, where the stone came from, namely, Neuburg-on-the-Danube.

The geological map of Bavaria confirmed my worst fears, the Danube valley and, indeed, a good deal of southern Bavaria is an alluvial nightmare, however, just south-west of Neuburg there is an outcrop of Jurassic dolomite limestone from the Oxfordian, this can be the only possible location for the quarry. This is in fact the same sediment that outcrops over an extensive part of the Fraenkische Alb, Schwaebische Alb and into the Swiss Jura, following roughly the palaeocoastline of a branch of what today is the North Sea and it is also the same stone as found in Solnhofen, the home of Archaeopteryx lithographica. Southern Bavaria was positioned at a latitude of around 30° N during the Oxfordian, equivalent to about Cairo today. Armed with the age of my find, some 154-159 Ma, my book of fossils offered me a choice of about 20 different ammonite species, from the Oxfordian period. The book contains good photos of the specimens and details such as typical body shapes and sizes etc., I am fairly sure that I have been able to identify my specimen as Perisphinctes plicatilis, mainly, because of the forks at the end of its ribs.

The next day saw me drawn back magnetically to my favourite pile, however, the bulldozer had already been at work and the slabs and boulders were spread over the new embankment and firmly pressed down. Before leaving the site, I turned over the top-half of one of the smaller slabs, which had been neatly split in two, during the bulldozing. I was rewarded with the relief and impression, both complete and perfect, of a second Perisphinctes plicatilis plus two other mollusca or brachiopoda. Getting these samples home was something of a logistical problem, since each half-slab weighed about 15 kg, and I was now on the other, more distant river bank. The logistics were finally sorted out and solved with two cycle trips and a large ruecksack.

In the mean time, the two unmanagable 15 kg half-slabs have each been reduced to a reasonable size, exposing traces of many more ammonites. Also, one of the two unknown mollusca/brachiopoda has been further exposed and I think that there is a good chance of identifying it, although I have not come up with a final answer yet. It is about 3.5 cm long, with a width of 1.5 cm at its widest point. It looks very much in shape and texture, like the inside of a half of a brazil nut shell. It might be a brachiopod of the class Articulata, order Strophomenida and suborder Chonetidina,if anyone has any better idea what the beast could be, please let me know.

I felt that my finds more than compensated for the indignity of the mud-bath and I proudly wrote to our OUGS Spokesperson, Annette, claiming that this was an example of 'Real Geology'. I was promptly slapped down and informed by her that what I had practised was not "Real Geology", but 'Armchair Geology'. That is where you sit at home in your armchair and wait until a lorry dumps a load of fossils in your backyard, what else could I have expected from a volcano freak?

Mike Molloy, Munich