La Voulte-sur-Rhone

The late mid-Jurassic lagerstätte at La Voûlte-sur-Rhone, 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. Some soft parts of organisms are preserved as phosphatised concretions, in exceptional cases down to cellular details. [ [http://palaeo.gly.bris.ac.uk/Palaeofiles/Lagerstatten/lavoulte/index.html (Department of Earth Sciences at University of Bristol): Sarah Joomun, "La Voûlte-sur-Rhone"] ; Etter 2002 notes some retinal structures in the eyes of conchilyocaridi crustacea.]

The facies are exposed in a series of quarries at La Boissine, west of the village of La Voûlte-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.

At the site, well-preserved fossils of the first pycnogonids ("sea-spiders") ever found in Mesozoic strata were identified in 2007. [Pycnogonids have a very patchy fossil record. S. Charbonnier, J. Vannier and B. Riou, "Jurassic sea spiders from the La Voulte-sur-Rhône Lagerstätte" "Proceedings of the Royal Society of London" B 274, reported in "Geophysical Research Abstracts" 10 (2008) ( [http://www.cosis.net/abstracts/EGU2008/02378/EGU2008-A-02378.pdf?PHPSESSID= on-line abstract] ).] The oldest Coleoid cephalopods (squid and octopus [A single specimen of a small octopus, the oldest such fossil, was published in 1982 (Etter 2002).] ) were found here. Fish, crustaceans, and bivalves, which lived in mid-water levels and drifted down after they died, ophiuroids [Most commonly "Ophiopinna elegans" (Etter 2002).] and burrowing worms are all to be found. Periodic turbidity flows may have washed allochthonous organisms in from a more highly oxygenated benthic fauna. Turbidity flows and the presence of two specimens of plants suggest that a shoreline was not far distant, represented today by France's Massif Central (Etter 2002).

References

*Walter Etter, "La Voulte-sur-Rhone: exquisite cephalopod preservation", in David J. Bottjer, Walter Etter, "Exceptional Fossil Preservation: A Unique View on the Evolution of Marine Life" (Columbia University Press) 2002. Full description and bibliography of the site.

Notes