La Voulte-sur-Rhône (lagerstätte)
La Voulte-sur-Rhône | |
---|---|
Ma | |
Type | Geological formation |
Thickness | about 100 m (330 ft) |
Lithology | |
Primary | Claystones and marls |
Other | ferruginous limestone |
Location | |
Coordinates | 44°47′58.3″N 4°46′42.4″E / 44.799528°N 4.778444°E |
Region | Rhône-Alpes, Ardèche department |
Country | France |
Extent | Several historically active commercial quarries |
Type section | |
Named for | La Voulte-sur-Rhône, a nearby town |
The
Preservation
Some soft parts of organisms are preserved as phosphatised concretions, in exceptional cases down to cellular details, e.g. retinal structures in the eyes of conchyliocarid crustacea.[2] Apart from Beecher's Trilobite Bed and the Hunsrück Slate, La Voulte-sur-Rhône is the only other locality where extensive pyritization of soft parts occurs.[3] However, pyritisation is not the only preservation pathway; several stages of mineralization (originally phosphate followed by calcite or gypsum, then pyrite and finally galena) are seen, each successive mineralization event degrades the detail preserved, with only gross morphological features preserved in the most advanced stages.[4]
Fauna and flora
The fauna preserved can be broadly divided into the
The allochthonous fauna contains rare and well-preserved organisms.
The in situ mortality horizon consists of abundant pavements of the bivalve Bositra buchi and trace fossils of suspected worm burrows.
Two specimens of plants suggest that a shoreline was not far distant, represented today by France's Massif Central.[2]
References
- ^ Location as described in: Sylvain Charbonnier, Jean Vannier, Pierre Hantzpergue, Christian Gaillard. Ecological signif- icance of the arthropod fauna from the Jurassic (Callovian) La Voulte Lagerstätte. Acta Palaeontologica Polonica, Polskiej Akademii Nauk, Instytut Paleobiologii, 2010, 55 (1), pp.112. Online: https://hal.archives-ouvertes.fr/hal-00551274/document
- ^ a b c d Etter, Walter (2002), "La Voulte-sur-Rhône: exquisite cephalopod preservation", in David J. Bottjer; Walter Etter; James W. Hagadorn; Carol M. Tang (eds.), Exceptional Fossil Preservation: A Unique View on the Evolution of Marine Life., Columbia University Press, NY, pp. 293–306
- ISBN 978-0-226-74641-8, archived from the original(PDF) on July 14, 2011 see page 41
- ^ "La Voulte-sur-Rhone" by Sarah Joomun, Dept. of Earth Science, Bristol University
- ^ S. Charbonnier; J. Vannier; B. Riou (2007), "Jurassic sea spiders from the La Voulte-sur-Rhône Lagerstätte", Proceedings of the Royal Society of London, B 274: 2555–61
- ^ S. Charbonnier; J. Vannier; B. Riou (2008), "Jurassic sea spiders from the La Voulte-sur-Rhône Lagerstätte" (PDF), Geophysical Research Abstracts, 10