Reconstructing the Late Quaternary eruption history of the Chaîne des Puys, France, using modern luminescence dating approaches

• Applicants: Dr. Lennart Fischer; Professor Dr. Frank Preusser
• Subject Area: Palaeontology ; Mineralogy, Petrology and Geochemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 490668505

Volcanic hazard assessment studies benefit greatly from accurate and well-resolved chronologies of active volcanic provinces. By this is it possible to establish past temporal and spatial patterns in eruptions and allow for the refinement of models for the magmatic evolution of a province. The Chaîne des Puys in the Auvergne, France, is a prime example of a young volcanic province with the last eruption dating to 7130–6370 years ago. Considering its central location in France and proximity to the city of Clermont-Ferrand, a potential future eruption could have serious impacts on a large population. An additional appealing aspect of the Chaîne des Puys is its geoheritage value and recent designation as a UNESCO World Heritage Site in 2018. However, only a little less than half of all the eruptions in the Chaîne des Puys have been dated so far. Furthermore, a large majority of dates available are from the doctoral thesis of Guérin (1983), who used thermolumiescence dating. Since then, the luminescence dating has seen several major methodological refinements, which have now established the methods as a regular tool in geochronology.The primary objective of the project is to establish a revised and more reliable chronology of the Chaîne des Puys. The secondary objective of the study is to create a protocol to test the chemical, mineralogical, and luminescence properties of crystalline feldspars from volcanic samples in order to determine the optimum luminescence method to obtain a date. A three-phase research project with two side projects has been planned to achieve these two objectives. In the first phase petrographic and geochemical analysis will be performed on samples collected from several volcanoes in the Chaîne des Puys during a preliminary phase to understand the mineral textures and thermal histories of the samples. The second phase of the project will be a systematic analysis of the luminescence behavior of these same samples under various luminescence methods to identify relationships between a sample’s mineralogy and thermal history to its luminescence behavior. In the final phase, the results of the previous two phases will be compiled to devise the optimal luminescence protocol for each sample and ultimately derive final luminescence ages. The two side projects are important additions to the project to assure that the measured luminescence signal has not been reset since the event being dated, and to provide a reliable effective dose rate for the samples, which is necessary for dating calculations. The final ages obtained by this project will be integrated into volcanic risk assessments for the Chaîne des Puys and into the educational content related to the UNESCO geoheritage program. Additionally the impact of this project will extend beyond the Chaîne des Puys, because the protocol established for dating will be of significant value due to its applicability to luminescence dating of other Quaternary volcanic provinces.

• DFG Programme: Research Grants
• International Connection: France, Switzerland
• Cooperation Partners: Dr. Daniel Rufer; Professor Dr. Benjamin van Wyk de Vries