Lagerstätten

sedimentary deposit that exhibits extraordinary fossils with exceptional preservation
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Lagerstätte (plural: Lagerstätten) is a German word for places (sites) of exceptional fossil preservation. Adolf Seilacher coined the term in 1970 to describe sites, like Solnhofen, which yielded the most exceptional fossils.[1]

Diplomystus dentatus from the Green River Formation, an Eocene Lagerstätte
Marrella, the most abundant Burgess Shale organism

Extra-special sites are called Konservat-Lagerstätten (conservation Lagerstätten). These are deposits known for the exceptional preservation of fine details. There skeletons are mostly articulated (bones together in life form), and the soft parts are preserved as impressions or casts.

Preservation

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In Lagerstätten the normal processses of decay after death were less active or halted as sediment was deposited. This allowed the preservation of soft parts and exceptional detail. There are several possible causes which allow this to happen:

  1. Anoxic or near anoxic conditions (e.g. oxygen-free mud) which suppresses common bacterial decomposition long enough for the initial casts of soft body parts to register.
  2. Rapid burial in volcanic ash from a nearby eruption. This prevents scavengers and burrowing animals from reaching the dead body. It also produces a low-oxygen environment.
  3. Rapid burial by mud-slides.
  4. High salt content in the water, which few organisms can live in. This condition occurred in the lagoons which produced the Solnhofen limestone.

In these conditions, which are exceptional, scavengers, burrowers and bacteria are eliminated or reduced. Then the normal processes of deposition and fossilisation produces strata containing exceptional fossils.

Lessons learnt

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Most of what we know about the details of extinct life comes from these exceptional sites. The soft-bodied Ediacaran biota, the fins of ichthyosaurs, the fur and wing structure of pterosaurs, the feathers on Mesozoic dinosaurs and birds, are all discoveries made on fossils from Lagerstätten. These sites preserve much of the fauna and flora of the time and place. That permits reconstruction of its ecology.

Short-list of Lagerstätten

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Palaeovespa florissantia, a fossil wasp, forms the logo for Florissant Fossil Beds National Monument

There are over 50 sites which have been described as Lagerstätten.[2]

Bitter Springs, South Australia
Mistaken Point Ecological Reserve, Newfoundland, Quebec
Sirius Passet, Greenland.
Burgess Shale, British Columbia, Canada
Qingjiang biota, Hubei, China
Fezouata Formation, Morocco
Rhynie chert, Aberdeen, Scotland
Mazon Creek, Illinois;
Joggins Fossil Cliffs, Nova Scotia
Morrison Formation, western U.S.A.
Solnhofen limestone, Bavaria, Germany
Jehol biota: Yixian and Jiufotang formations, China.
Burmese amber fossils;
Smoky Hill Chalk: Zhucheng dinosaur site
Tanis, North Dakota: Tanis fossil site
Messel Pit, Germany
Green River Formation, Utah.
Florissant Formation, Rocky Mountains, Colorado
Riversleigh, Australia
Gray Fossil Site, Tennessee
Rancho La Brea tar pits, Los Angeles, California.

References

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  1. Seilacher A. 1970. Begriff und Bedeutung der Fossil-Lagerstätten: Neues Jahrbuch fur Geologie und Paläontologie. Monatshefte 1970: 34–39.
  2. "Fossil Lagerstätten". Department of Earth Sciences, University of Bristol. 2003. Archived from the original on 2007-06-12. 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.