Lagerstätte
A Lagerstätte (German; literally place of storage; plural Lagerstätten) is a sedimentary deposit that exhibits extraordinary fossil richness or completeness. Palaeontologists distinguish two kinds.[1]
Konzentrat-Lagerstätten (concentration Lagerstätten) are deposits with a particular concentration of disarticulated organic hard parts, such as a bone bed. These Lagerstätten are less spectacular than the more famous Konservat-Lagerstätten. Their contents invariably display a large degree of time averaging, as the accumulation of bones in the absence of other sediment takes some time. Deposits with a high concentration of fossils that represent an in-situ community, such as reefs or oyster beds, are not considered Lagerstätten.
Konservat-Lagerstätten (conservation Lagerstätten) are deposits known for the exceptional preservation of fossilized organisms, where the soft parts are preserved in the form of impressions or casts. This is caused by incompleteness of biological recycling, for example where anoxic conditions, as in oxygen-free mud, has suppressed common bacterial decomposition long enough for the initial casts of soft body parts to register. The individual taphonomy of the fossils varies with the sites. Conservation Lagerstätten are crucial in providing answers to important moments in the history and evolution of life, for example the Burgess Shale of British Columbia is associated with the Cambrian explosion, and the Solnhofen limestone with the earliest known bird, Archaeopteryx.
Preservation
Konservat-Lagerstätten preserve lightly sclerotized and soft-bodied organisms that are not otherwise preserved in the usual shelly and bony fossil record; thus they offer a more complete record of ancient biodiversity and enable some reconstruction of the palaeoecology of ancient aquatic communities. In 1986 Simon Conway Morris calculated that only about 14% of genera in the Burgess Shale had possessed biomineralized tissues in life. The affinities of the shelly elements of conodonts were mysterious until the associated soft tissues were discovered near Edinburgh, Scotland, in the Granton Lower Oil Shale of the Carboniferous.[2] Information from the broader range of organisms found in Lagerstätten have contributed to recent phylogenetic reconstructions of some major metazoan groups.
A number of taphonomic pathways may produce lagerstätten. Here's an incomplete list:
- Orsten type preservation and Doushantuo type preservation preserve organisms in phosphate
- Bitter Springs type preservation preserves them in silica
- Carbonaceous films are the result of Burgess Shale type preservation
- Pyrite preserves exquisite detail in Beecher’s Trilobite type preservation
- Ediacaran type preservation preserves casts and moulds with the aid of microbial mats.
Important Lagerstätten
The world's major Lagerstätten include:
See also
- List of fossil sites (with link directory)
References
- ^ The term was originally coined by Adolf Seilacher here: Seilacher, A. (1970). "Begriff und Bedeutung der Fossil-Lagerstätten: Neues Jahrbuch fur Geologie und Paläontologie" (in German). Monatshefte 1970: 34–39.
- ^ Briggs et al. 1983; Aldridge et al. 1993.
References
- "Fossil Lagerstätten". Department of Earth Sciences, University of Bristol. 2003. http://palaeo.gly.bris.ac.uk/Palaeofiles/Lagerstatten/. Retrieved 2005-11-21. — A catalogue of sites of exceptional fossil preservation produced by MSc palaeobiology students at University of Bristol's Department of Earth Sciences.
- Orr, Patrick J.; Derek E. G. Briggs, David J. Siveter and Derek J. Siveter (1 January 2000). "Three-dimensional preservation of a non-biomineralized arthropod in concretions in Silurian volcaniclastic rocks from Herefordshire, England". Journal of the Geological Society 157 (1): 173–186. http://jgs.geoscienceworld.org/cgi/content/abstract/157/1/173. Retrieved 2006-10-26.