Puy de Paugnat
| Puy de Paugnat | ||
|---|---|---|
| height | 896 m | |
| location | Puy-de-Dôme department , France | |
| Mountains | Chaîne des Puys , Massif Central | |
| Coordinates | 45 ° 52 '49 " N , 2 ° 58' 40" E | |
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| Type | Cinder cone | |
| rock | Trachy basalt | |
| Age of the rock | 30,600 ± 3,400 years BP | |
The Puy de Paugnat is an extinct volcano ( cinder cone ) in the French department of Puy-de-Dôme , which belongs to the Chaîne des Puys .
Geography
The Puy de Paugnat belongs to the municipality of Charbonnières-les-Varennes ( Auvergne-Rhône-Alpes region ) and is located 500 meters southwest of the eponymous district of Paugnat . Moulet-Marcenat , part of the municipality of Volvic, is 1.5 kilometers to the east . The cinder cone is surrounded by other volcanic structures, such as the Puy de la Nugère 2.5 kilometers in the south-south-east, from which it is separated by the Bois Latia forest , the Puy de la Gouly and the Puy la Baneyre 1.5 kilometers in the south-west, the Puy de Pradet 1 kilometer in the west and the Puy de Verrières and the Puy du Thiolet 2 kilometers in the northwest. The D 16 / D 90 passes on its north side and the railway line from Clermont-Ferrand to Montluçon and Mont-Dore in the south runs on its south-west side . A circular hiking trail leads around the volcano, part of which is used on the GR 4411 long-distance hiking trail.
geology
introduction
The Chaîne des Puys is the youngest volcanic district in France with typical alkaline intraplate volcanism. It can boast over 100 volcanic centers that were created over an arched eyrie of the Variscan basement , the Plateau des Dômes . This plateau consists of rhyolite tuffs of the Viséum in the north , but further south of peralkalic granitoids of the Upper Carboniferous and migmatic gneisses of the early Paleozoic. It is bounded to the east by the Limagne Trench and to the west by the Olby Trench (Fossé d'Olby). The volcanoes are lined up over a distance of 30 kilometers in a 3 to 4 kilometer wide band in north-south direction and thus run parallel to the edge fault of the Limagne Trench.
Volcanism began at the beginning of the Würm Ice Age around 100,000 years BP and lasted up to almost 4,000 years BP, with the majority of the volcanic centers being formed between 13,500 and 7,000 years BP, with a maximum of 10,000 years BP for the basalts. It is questionable whether it is now completely extinguished.
The extracted magmas form a series of magmas differentiated by fractional crystallization , which ranges from potassium-rich alkali basalts to mugearite and benmoreite (rarely) to trachytes . A total of around 8 cubic kilometers of basaltic lavas and 1 to 2 cubic kilometers of trachy derivatives as viscous lava domes were formed.
description
The Puy de Paugnac is located in the northern section of the Chaîne des Puys, a little to the east separated from the main chain. The rounded cinder cone culminates at 896 meters above sea level and towers over the surrounding plain by around a hundred meters. In contrast to the other volcanoes of the Chaîne des Puys, however, its summit has no crater. Its slopes are wooded with the exception of the northeast side, which has now been completely dismantled by a large quarry. The quarry had been quarrying the pozzolans over an area of 11.8 hectares for over 50 years , but was finally closed in 2001.
The quarry provides an excellent insight into the internal structure of a Strombolian volcano. The stratification of the scoria falls parallel to the slope of the cone at an angle of 30 ° radially outwards from the center - the natural angle of incidence of loose material. Two facies merging into one another can be distinguished - a core facies, whose red-colored scoria shows the oxidation of the iron in the sediments, and a black- colored , reduced marginal facies. The mean grain sizes changed in the course of the eruption and thus reveal differently strong eruption pulses. Under the pozzolana there are spindle-shaped bombs of various sizes and fragments of lava that are beautifully twisted in flight.
Dating
By means of thermoluminescence, Guérin (1983) found an age of 30,500 ± 7,000 years BP for the Puy de Paugnat , which means that it erupted towards the end of the Würm Ice Age. Similarly, Brousse and Levfevre (1990) were able to determine an age of 30,600 ± 3,400 years BP using thermoluminescence. Sampling south of the D 16 at Moulet-Marcenat by Guérin showed 30,550 ± 3,500 years BP using TL.
Individual evidence
- ↑ Villemant, B. et al .: Cristallisation fractionnée d'un magma basaltique alcalin: la série de la Chaîne des Puys (Massif Central, France). II. Geochimie. In: Bulletin de Minéralogie . tape 103 , p. 267-286 .
- ↑ Boivin, P. et al.: Volcanologie de la Chaîne des Puys, Massif Central Français (58 edition) . Parc Naturel Régional des Volcans d'Auvergne, Clermont-Ferrand 2009, p. 196 .
- ↑ a b Guérin, G .: La thermoluminescence des plagioclases, méthode de datation du volcanisme. Applications au domaine volcanique français: Chaîne des Puys, Mont Dore et Cézallier, Bas-Vivarais. (PhD thesis) . Université Pierre et Marie Curie - Paris VI, Paris 1983.
- ^ Brousse, R. and Lefevre C .: Le Volcanisme en France . Masson (Guides Géologiques Régionaux), Paris 1990.