Exquisite Cephalopod Preservation
THE MARINE LAGERSTÄTTE OF LA VOULTE-SUR-RHÔNE IS poorly known outside France, even though generations of paleontologists and geologists have worked at this locality. The Callovian (Middle Jurassic) of La Voulte, a series of dark platy claystones and marls with intercalated ferruginous limestone layers and carbonate concretions, is especially notable for the excellent preservation of ophiuroids, crustaceans, and fish, as well as perhaps the finest examples known of fossil cephalopods exhibiting soft-part preservation. Apart from Beecher's Trilobite Bed (Chapter 7) and the Hunsrück Slate (Chapter 8), La Voulte-sur-Rhône is the only other locality where extensive pyritization of soft parts occurs (Bartels, Briggs, and Brassel 1998). However, soft-part preservation in La Voulte-sur-Rhône is not confined to pyritization, but also occurs associated with phosphatized and calcified tissues (Wilby, Briggs, and Riou 1995, 1996). The exceptional preservation in this locality in southeastern France is most likely the result of both oxygen-depleted bottom-waters and repeated sediment blanketing. This Lagerstätte thus qualifies as both a stagnation and an obrution deposit (sensu Seilacher, Reif, and Westphal 1985).
Interest in the fossiliferous layers of La Voulte-sur-Rhône dates back to the early nineteenth century. At that time, the ferruginous beds were exploited as iron ore, and as a result, various geologists tried to establish the stratigraphic position of these layers (Sayn and Roman 1928). By the middle of the nineteenth century, the first remarkable fossils were discovered, including the bedding-plane accumulations of fully articulated ophiuroids (Lory 1854). Although the stratigraphy of the Callovian of