Jura Threshold
The Jura threshold—At the crossroads of the Mesozoic seas
This project aims to update our knowledge:
- On the revision and ammonite dating of the various lithostratigraphic units of the Jura Range;
- On the description of previously unknown species and their phylogenetic relationships;
- On the faunal exchanges occurring between the Tethysian and Boreal marine domains via the Jura-Burgundy Threshold, an underestimated paleogeographic crossroads.
The Jurassic: Inventory of Lower Lias ammonites from the Jura Massif — Many studies devoted to the Lower Jurassic in the Jura Massif mention ammonites only in the form of taxonomic lists, often lacking illustrations, which limits their verifiability and comparative scope. A preliminary inventory aims to review and illustrate, for the first time in a comprehensive manner, a large portion of the species recognized in the Jura.
This collection sheds new light on ammonite biodiversity and offers a coherent view of the biostratigraphic and paleobiogeographic framework of the Lower Jurassic in the western part of the Jura Massif. In particular, it highlights episodes of migratory fluctuations between the Tethysian and Boreal regions, which were especially pronounced during the Hettangian–Sinemurian and the Toarcian, in connection with phases of increased connectivity between basins.
The Cretaceous: Since the late 19th century, numerous authors have reported the presence of boreal ammonites in Cretaceous sediments of southeastern France and vice versa. The stratigraphic and paleogeographic distribution of ammonite families on the Jura threshold is a very good indicator of migration routes and their chronology. The factors that controlled the distribution of boreal ammonites along the northern margin of the Tethys and vice versa are not yet fully understood (paleogeographic barriers, paleo-oceanographic and climatic changes, and paleoecological adaptations).
Project Leader : Antoine Pictet
