The late Middle Jurassiclagerstätte at La Voulte-sur-Rhône, in the Ardèche region of southwestern France, offers paleontologists an outstanding view of an undisturbed paleoecosystem that was preserved in fine detail as organisms died at the site and settled to the bottom of a shallow epicontinental sea, with a folded floor that in places exceeded 200 m at this site. The site preserves a marine system of the Lower Callovian stage, a little over 160 mya. The sequence is exposed in a series of quarries at La Boissine, west of the village of La Voulte-sur-Rhône. Iron pyrites in the silty shale are symptoms of an anoxic environment. The site was recognized among French paleontologists from the mid-nineteenth century for its finely detailed fossils.
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 allochthonous fauna (consisting of soft-bodied organisms which lived on the sea floor (benthic) or swam freely just above it (nektobenthic)) and the in-situ mortality horizon.
The allochthonous fauna contains rare and well-preserved organisms. Fossils of pycnogonids ("sea-spiders"), the first find in Mesozoic strata in an admittedly very patchy fossil record, were identified in 2007.[5][6] A coleoidcephalopod (a single specimen of a small octopus) was described from La Voulte-sur-Rhône in 1982.[2] The marine crocodile Metriorhynchus, fish, decapod, mysidcrustaceans, thylacocephalans, crinoids, and ophiuroids (most commonly Ophiopinna elegans)[2] are also to be found.
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
^ abcdEtter, 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
^Paul A. Selden; John R. Nudds (2005), (PDF), University of Chicago Press, IL, p. 192, ISBN978-0-226-74641-8, 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
June 25, 2023
voulte, rhône, lagerstätte, late, middle, jurassic, lagerstätte, voulte, rhône, ardèche, region, southwestern, france, offers, paleontologists, outstanding, view, undisturbed, paleoecosystem, that, preserved, fine, detail, organisms, died, site, settled, botto. The late Middle Jurassic lagerstatte at La Voulte sur Rhone in the Ardeche region of southwestern France offers paleontologists an outstanding view of an undisturbed paleoecosystem that was preserved in fine detail as organisms died at the site and settled to the bottom of a shallow epicontinental sea with a folded floor that in places exceeded 200 m at this site The site preserves a marine system of the Lower Callovian stage a little over 160 mya The sequence is exposed in a series of quarries at La Boissine west of the village of La Voulte sur Rhone Iron pyrites in the silty shale are symptoms of an anoxic environment The site was recognized among French paleontologists from the mid nineteenth century for its finely detailed fossils La Voulte sur RhoneStratigraphic range Callovian 165 Ma PreꞒ Ꞓ O S D C P T J K Pg N The mines ravine of the Voulte lagerstatte 1 TypeGeological formationThicknessabout 100 m 330 ft LithologyPrimaryClaystones and marlsOtherferruginous limestoneLocationCoordinates44 47 58 3 N 4 46 42 4 E 44 799528 N 4 778444 E 44 799528 4 778444RegionRhone Alpes Ardeche departmentCountryFranceExtentSeveral historically active commercial quarriesType sectionNamed forLa Voulte sur Rhone a nearby townPyritized fossil of Vampyronassa rhodanica from La Voulte sur RhonePreservation Edit Rhomboteuthis lehmani from La Voulte sur Rhone 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 Hunsruck Slate La Voulte sur Rhone 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 EditThe fauna preserved can be broadly divided into the allochthonous fauna consisting of soft bodied organisms which lived on the sea floor benthic or swam freely just above it nektobenthic and the in situ mortality horizon The allochthonous fauna contains rare and well preserved organisms Fossils of pycnogonids sea spiders the first find in Mesozoic strata in an admittedly very patchy fossil record were identified in 2007 5 6 A coleoid cephalopod a single specimen of a small octopus was described from La Voulte sur Rhone in 1982 2 The marine crocodile Metriorhynchus fish decapod mysidcrustaceans thylacocephalans crinoids and ophiuroids most commonly Ophiopinna elegans 2 are also to be found 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 Edit 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 Lagerstatte 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 Rhone 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 Paul A Selden John R Nudds 2005 Evolution of Fossil Ecosystems PDF University of Chicago Press IL p 192 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 Rhone Lagerstatte 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 Rhone Lagerstatte PDF Geophysical Research Abstracts 10 Retrieved from https en wikipedia org w index php title La Voulte sur Rhone lagerstatte amp oldid 1129326434, wikipedia, wiki, book, books, library,
