|Name: The Solnhofen Lithographic Limestone
Location: Bavaria, Germany
Age: Tithonian, Late Jurassic
The Solnhofen Lithographic Limestone group is located in the Southern Franconian Alb in the German State of Bavaria, in the region of Nuremberg and Munich. The majority of this bed is exposed in the many local quarries, where the locals mine the fine-grained flat-cleaving limestone, or "Plattenkalk", for floor and roof tiles and lithographic plates in printing. The miners often find fossils, which are then sold on to tourists and scientists.
Geological setting and age:
The lithology is characterised by micritic, even layered limestone slabs ("Flinze"), and irregular intercalated calcareous fine-layered marls ("Fäulen"). There is some controversy over the origin of the sediment, with Barthel (1978) believing that the Fäulen represents normal deposition, and the Flinze represents storm deposits, whereas others believe that they are built up as a type of stromatolite (Keupp, 1977). The first hypothesis seems to be more likely, with carbonate ooze being deposited on the seaward margin of the coral reefs being periodically stirred up by storms and being introduced by suspension into the lagoon, forming a fine mud when it settled.
The Solnhofen Lithographic Limestone was deposited in the Tithonian age of the Jurassic period, in a small lagoon where water exchange was restricted from the open sea due to an extended platform of shallow water and strong seafloor relief. A hot dry climate caused high evaporation rates, which in turn led to extremely saline conditions in the basins and the development of salinity stratification.
The bottom would have been hypersaline, stagnant and anoxic, whereas the upper levels of the water column were of normal salinity, allowing both nekton (swimming organisms) and plankton (floating organisms) to thrive. There were also some benthic (bottom dwelling) organisms that lived on ancient sponge-microbial mounds that entered the well-aerated upper waters, which are represented by both body fossils and trace fossils.
Fauna and flora:
The vast majority of Solnhofen fossils are complete, with soft tissue preservation. This would confirm the suggestion that there was rapid sedimentation, represented by the Flinze, with gradual sedimentation being represented by the Fäulen. The fossils show many necrolytic features that could be due to the hypersaline nature of the environment. For example, many of the teleost fish are bent quite strongly, with the vertebral column being broken as a result, and the curved-back necks of the flying vertebrates may also be a result of osmotic desiccation, although this may also be due to the drifting position of the organism.
Evidence for hypersalinity also comes from the state of preservation of the commatulid crinoid Saccocoma. The majority of Saccocoma found in the Solnhofen Lithographic Limestone are preserved with their arms coiled up, whereas a few have them open. It has been deduced that if Saccocoma, like all other echinoderms, was able to move its arms using hydrostatic pressure, died and sank into deeper, more saline water, the loss of water from Saccocoma by osmosis in the hypersaline waters below the halocline would cause this collapse.
There is evidence for quick death in several specimens. In some of the fish and pterosaurs there are stomach contents, and even in one case of a fish on the process of swallowing another. There are also half-eaten fish, possibly the leftovers of a fish or pterosaurs dinner. Also, there are examples of fish that are wrapped in microbial film, which would have passed through the halocline, and therefore the microbial film after death, although this is not very common.
Aragonite is not preserved in the Solnhofen Lithographic Limestone, with the ammonites being deformed and reduced to periostracal films, presumably in the upper levels of the water column, as these are more commonly preserved in slump sediments.
BARTHEL, K. W. 1978. Solnhofen. Ein Blick in die Erdgeschichte. Ott Verlag, Thun.
KUEPP, H. 1977. Ultrafazies und Genese der Solnhofener Plattenkalke (Oberer Malm, Südliche Frankenalb). Abhandlungen der Naturhistorischen Gesellschaft Nürnberg. 37, 128
SEILACHER, A., ANDALIB, F., DIETEL, G and GOCHT, H. 1976. Preservational history of compressed Jurassic ammonites from southern Germany. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 152, 307-356
VIOHL, G. 1990. Solnhofen Lithographic Limestones. In BRIGGS, D. E. G. and CROWTHER, P. R. (eds). Palaeobiology: a synthesis. Blackwell Science. 285-289
óóóó. 1998. The Fossils of the Solnhofen Lithographic Limestone. Brief Guide. Jura-Museum, Eichstätt, Willibaldsburg. Bischöfliches Seminar, St. Willibald, Eichstätt.
DYKES, T. 2002. The Museums of Solnhofen. http://home.arcor.de/ktdykes/altmuehl.htm
Kennedy 2000 - Solnhofen Limestone Home of Archaeopteryx: http://www.grisda.org/georpts/3001.htm
Solnhofen, Germany: http://www.yale.edu/ypmip/locations/solnhofen.html
Section author: Simon M. Clabby
This section is part of a Fossil Lagerstätten web site which has been built up as a result of the efforts of the 2002-3 MSc Palaeobiology class in the Department of Earth Sciences at University of Bristol, as part of a course in Scientific Communication.
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