The Chaîne des Puys: how complicated can monogenetic get?

VAN WYK DE VRIES, B.; GROSSE, P.; MARQUEZ, A.; PETRONIS, M.S.; KERVYN, M.; DELCAMP, A.; MOSSOUX, S.; TROLL, V.

San Francisco

Congreso; American Geophysical Union 2012 Fall Meeting; 2012

American Geophysical Union

The Chaîne des Puys (Massif Centrale of France) is part of a prospective volcano-tectonic UNESCO World Heritage site including the Limagne Rift fault (http://www.chainedespuys-failledelimagne.com/). The strategy is to present the monogenetic field that is both representative of other such fields but also uniquely special. Effectively, the Chaîne des Puys would become a sort of ambassador for monogenetic volcanism, raising the profile of all other sites. Here, we want to go through some recent work on the chain, looking at morphology, morphometry, structure, lithology and petrology and show some of the intriguing complexities of this classic highly variable monogenetic alignment. Also, we want to build on the historical development of ideas that can be traced back to characters such as Montlosier, Humphrey Davey, Faraday, Lyell, and Von Humbolt... and many more. We focus, first, on the central Puy de Dôme. This classic trachyte dome has been known for some time to be the product of two eruptions, and recently we have found that it is related to a number of cryptodome intrusions that have created two flanking bulges, fed at least two major explosive eruptions, and extensively modified the topography of the field. Strangely, Von Humbolt´s concept of  ´craters of elevation´ rises up in a reanalysis of these structures. Secondly, we visit Lemptégy (www.auvergne-volcan.com/), which in 1857 Scrope called ´an insignificant cone grazed by sheep´, but now quarried out and showing the internal structure expected for the Puy de Dôme bulges, as well as illustrating that a seemingly simple scoria cone plumbing can be infernally complicated. Thirdly, we consider the Beaunit, a bucolic village in a maar, where the process of crustal ingestion suggests an intimate relationship between eruptive dynamics and assimilation. With these three examples we show some of the complications and interactions of monogenetic basaltic to trachytic volcanism typified by the Chaîne des Puys.