Structural control of the Limagne Rift Fault on the Chaîne des Puys

The close proximity of the Limagne Fault to the Chaîne des Puys (Massif Central, France) has been noted for a long time. In fact, if the Limagne fault had not raised the Chaîne relative to the Limagne Rift, to create a spectacular skyline of volcanoes, there would probably not have been so much interest in them. Early geologists such as Elie de Beaumont, Davy, Lyell, Murchison, and Von Humbolt, were as much concerned with explaining the escarpment by catastrophism or uniformitarianism, as they were with battling over neptunism and plutonism, or craters of elevation. The questions still stands as to what relationship the monogenetic volcanoes have to the fault, and perhaps: are the volcanoes monogenetic because of the fault? - seeing as just to the south of the rift, stand the Mont Dore-Sancy and Cantal stratovolcanoes. Considering the spatial-temporal relationship, it becomes clear that there are volcanoes on the fault, in the rift, and behind the footwall, but with different ages and configurations. Early volcanoes are cut by the faulting, showing a potential linkage, later volcanoes, as a whole, follow generally the main structural trend NS of the rift, but in detail group around a more NE-SW trend, that can be related to Hercynian structures, and to a major transfer fault linking the Limagne Rift to the Rhine Graben. These trends host some of the youngest volcanoes, and the fault appears to have been more recently active in this area, and the area of some damaging historic earthquakes. Considering the proximity of the fault as an influence in the monogenetic nature of the volcanism, more needs to be known about the state of faulting in the Tertiary in the Massif Central. However, the area of the Chaîne de Puys is highly heterogeneous, with complex associations of Hercynian and Tertiary structures, and thus the crustal structure may be compatible with multiple pathways, and thus a monogenetic tendency. In conclusion, there is a probably spatial and temporal structural link between the the Chaîne des Puys and the Limagne Rift, partly inherited for both from the Hercynian crust and lithosphere.