Solnhofen limestone
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A brittle star fossil from Solnhofen limestone. |
The
Solnhofen limestone is a
Jurassic lagerstätte that preserves a rare assemblage of
fossilized organisms, some of which, such as sea jellies, don't ordinarily fossilize at all. Others, like the early
bird Archaeopteryx are preserved in such detail that they are among the most famous and most beautiful fossils in the world.
The Solnhofen beds lie in the
German state of
Bavaria, halfway between
Nuremberg and
Munich. During late
Jurassic times, this area was an
archipelago at the edge of the
Tethys Sea. This included placid lagoons that had limited access to the open sea and where salinity rose high enough that the resulting brine could not support life. Since the lowest water was devoid of
oxygen, many ordinary scavengers were absent. Any organism that fell, drifted, or was washed into the lagoons from the ocean or the land became buried in soft
carbonate mud. Thus, many delicate creatures avoided consumption by scavengers or being torn apart by currents. The wings of
dragonflies, the imprints of stray
feathers, and terrestrial plants that washed into the lagoons were all preserved. The fossils are not numerous, but some of them are spectacular, and their range gives a comprehensive picture of a local Jurassic
ecosystem.
At times, the lagoons almost dried out, exposing sticky carbonate muds that trapped insects and even a few small
dinosaurs. Over 600 species have been identified, including twenty-nine kinds of
pterosaur ranging from the size of a sparrow to
1.2 m (4 ft) in length have been found.
The fine-grained texture of the mud
silt forming the
limestone from the
Solnhofen area (which is composed mainly of the towns of
Solnhofen and
Eichstätt)is ideal for making
lithographic plates, and extensive quarrying in the
19th century revealed many fossil finds, as commemorated in the name
Archaeopteryx lithographica, all the specimens of which come from these deposits.
*
University of California Berkeley offers a brief introduction.*
Another brief description.
