revised chronology of the youngest volcanoes of the
Transcription
revised chronology of the youngest volcanoes of the
Quaternaire, 23, (4), 2012, p. 283-290 REVISED CHRONOLOGY OF THE YOUNGEST VOLCANOES OF THE CHAÎNE DES PUYS (FRENCH MASSIF CENTRAL) n Didier MIALLIER1,6, Thierry PILLEYRE6, Serge SANZELLE6, Pierre BOIVIN2,3,4 & Philippe LANOS5 ABSTRACT The chronology of major, young (< 15 ka) volcanoes of the central part of the Chaîne des Puys has been revised by means of tephrostratigraphy, thermoluminescence dating and radiocarbon dating. The previously assumed relative chronology between volcanoes like Pariou and Chopine was inverted; more accurate numerical ages were obtained, as exampled in the case of Côme volcano. This revision also includes previously unknown eruptions. Compilation of all available data suggests that an active volcanic period, marked by about two to three eruptions per millennium, terminated about 7 ka ago. This is an issue for interpreting the volcanism of the Chaîne des Puys during both Upper Pleistocene and Holocene. It seems to mark the end of a cycle, initiated about 80 ka ago, of feeding from a deep reservoir before magma differentiation in a system of shallow level magma chambers. Keywords: Chaîne des Puys, volcanoes, tephrochonology, radiocarbon, thermoluminescence RÉSUMÉ RÉVISION DE LA CHRONOLOGIE DES VOLCANS LES PLUS JEUNES DE LA CHAÎNE DES PUYS (MASSIF CENTRAL FRANÇAIS) La chronologie relative et absolue de volcans majeurs et récents (< 15 ka) du centre de la Chaîne des Puys a été révisée par une approche téphrostratigraphique combinée à la datation par thermoluminescence et par radiocarbone. La chronologie relative précédemment admise entre certains volcans comme le Pariou et le Chopine a été inversée ; des âges plus précis ont été obtenus, par exemple pour le Côme ; enfin, la révision introduit des éruptions qui n’avaient pas encore été repérées. Le schéma chronologique permet de mettre clairement en évidence le fait qu’une période de volcanisme actif, comprenant autour de deux à trois éruptions par millénaire, s’est achevée il y a environ 7 000 ans. C’est un élément de réflexion pour l’interprétation du volcanisme pléistocène supérieur et holocène de la Chaîne des Puys. Ce volcanisme semble à la fin d’un cycle commencé il y a environ 80 000 ans par une alimentation profonde suivie par une différentiation magmatique dans un système de chambres intermédiaires. Mots-clés : Chaîne des Puys, volcans, téphrochonologie, radiocarbone, thermoluminescence 1 - INTRODUCTION The Chaîne des Puys is a small Quaternary volcanic field situated in the northern part of the continental intraplate volcanic area of the French Massif Central (Boivin et al., 2009). It is basically composed of about hundred monogenic volcanoes aligned westwards along the boundary between the Plateau des Dômes uplifted Palaeozoic block and the rift formed by the Limagne Graben (fig. 1). The volcanic centres display a variety of types resulting from different combinations of magma nature, presence or absence of external (i.e., nonmagmatic) water and pre-existing topography (either volcanogenic or not). The principal volcanic types are basaltic (s.l.) scoria cones accompanied by lava flows, basaltic or trachytic maars, as well as trachytic lavadomes and protrusions. The magma diversity resulted from differentiation occurring in intermediate chambers, where magma possibly stayed for long periods before rising up to the surface. Crustal contamination may also have played a role in the evolution of the magma composition (Condomines et al., 1982). Clermont Université, Université d’Auvergne, LPC, CNRS/IN2P3, F-63177 AUBIERE cedex. Courriel : [email protected] Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans, BP 10448, F-63000 CLERMONT-FERRAND. Courriel : P.Boivin@[email protected] 3 CNRS, UMR 6524, LMV, 5 rue Kessler, F-63038 CLERMONT-FERRAND 4 IRD, R 163, LMV, 5 rue Kessler, F-63038 CLERMONT-FERRAND 5 CNRS UMR 5060 Institut de Recherche sur les Archéomatériaux (IRAMAT), Centre de Recherche en Physique Appliquée à l’Archéologie (CRPAA), Université Bordeaux 3. Esplanade des Antilles, F-33607 PESSAC, Courriel : [email protected] 6 Clermont Université, Université Blaise Pascal, LPC, CNRS/IN2P3, F-63177 AUBIERE cedex 1 2 Manuscrit reçu le 10/09/2011, accepté le 19/06/2012 1210-126 Mep 4-2012.indd 283 26/11/12 10:06 284 quoted at ± 95 %. Quoting a single mean age with error limits is not exactly correct for radiocarbon because age distributions are quite complex, but this simplification gives homogeneity and clarity to the text. 2 - THE VOLCANOES AND TEPHRAS OF INTEREST 2.1 - VOLCANOES Fig. 1: General map of the Chaîne des Puys. For details, see Boivin et al. (2009). Fig. 1 : Carte générale de la Chaîne des Puys. Pour les détails, voir Boivin et al. (2009). Assessing both numerical and relative chronologies of these volcanoes has been an issue for a long time and this chronology has been periodically revised (e.g., Juvigné & Gilot, 1986; Juvigné, 1987a, b; Juvigné et al., 1988, 1992, 1994, 1996; Raynal et al., 1994; Vernet & Raynal, 2000; Miallier et al., 2004a, b, c). As a continuation, the present paper gives a revised chronology for the youngest volcanoes of the centre of the Chaîne des Puys, based on recent field observations and new dating results. It focuses on three major volcanoes, namely Puy de Côme, Puy Pariou, and Puy Chopine. Other volcanoes and tephra layers are also considered, where appropriate. The approach was based on tephrostratigraphy, thermoluminescence dating (TL) and radiocarbon dating. Only new data will be presented in detail. The present work focuses on proximal tephras, sampled on the volcanoes themselves or in their immediate vicinity. Actually, a substantial amount of data has already been obtained from long distance airborne tephras, trapped in various sediments (e.g., Reille et al., 1985; Juvigné, 1987b; Gewelt & Juvigné, 1988; Juvigné, 1991; Raynal et al., 1994; Vernet & Raynal, 2000; Fourmont et al., 2006). However, although the latter distal deposits have been characterized and dated, many of them could not yet be connected to specific volcanoes. In this paper, calibration of radiocarbon data was performed based on Reimer et al. (2004). Calibrated radiocarbon and TL ages are given as elapsed time before today (see discussion in Duller, 2011) with error limits 1210-126 Mep 4-2012.indd 284 The volcanoes of interest are succinctly presented below (details and map in Boivin et al., 2009). Puy de Côme and Puy Pariou (fig. 1) are both trachyandesitic cones accompanied by important lava flows. The construction of Puy Pariou comprised a first phreatomagmatic phase and a final strombolian phase. The first phase magma was trachyte and turned to trachyandesite in the course of eruptions, indicating the existence of a zoned reservoir (Camus, 1975; El Arabi, 1987). The eruptions were triggered or enhanced by interaction of magma with water, resulting in a tuff-ring and in thick distal tephra deposits characterised by phreatomagmatic features (Camus, 1975; El Arabi, 1987; Miallier et al., 2008). The cone was finally constructed by trachyandesitic strombolian projections, while lava flows were emitted eastwards and attained the Limagne plain. Puy de Dôme, the most prominent volcano of the Chaîne des Puys, is a trachytic lava-dome of which the erection was characterised by numerous but low energetic pyroclastic flows. Puy Chopine is a rhyolithic protrusion. Its eruptions were violent and affected a large area all around the volcano, eventually developing mudflows downwards to the Limagne Graben, as far as 11 km away from the eruption centre (Vernet et al., 2001, Vernet & Raynal, 2002). Puy Sarcoui, Aumône and Clierzou are trachytic cumulo-domes of which the growth has been quite calm, without significant pyroclastic flows. Vasset and Kilian are both trachytic volcanoes of which the eruptions gave rise to violent pyroclastic flows initiated by phreatomagmatic eruptions. Today, they both show only small and hidden dome remains but their tephras are thick and widespread all over the central area of the Chaîne des Puys (Boivin et al., 2009). Thin layers of ashes attributed to either Vasset or Killian, which respective products still cannot be discriminated from each other (Michon, 1996), were observed at long distance, as far as in Swiss lake-sediments (Martini & Duret, 1965). The Nid de la Poule is a 50 m wide basaltic maar, half surrounded by a crescent-shaped tuff ring. It is situated in the middle of the still poorly understood strombolian ensemble of Petit Puy de Dôme. The twin volcanoes La Vache and Lassolas, situated at the south of the Chaîne des Puys, are trachybasaltic cones that erupted simultaneously and produced a 16 km long lava flow. 2.2 - ORPHAN TEPHRA LAYERS In some cases, the chronological relationship between identified tephra layers implies intermediate tephras of unknown origin. Such tephras are briefly presented below. 26/11/12 10:06 285 3 - TEPHROSTRATIGRAPHIC DATA The Terrenoire tephra was primarily characterized 1,500 m west of the Puy de Dôme (fig. 1). It consists of poorly bedded layers of polygenic lapilli in which juvenile trachyandesitic lava, under the form of pumice, scoriaceous lapilli and lithics, is mixed with older basaltic lava and country rocks. This tephra, which has clearly a phreatomagmatic origin, is represented by thick units (often > 80 cm) in various places including the SE flank of the Puy de Barme and the flanks of the poorly known trachybasaltic volcanoes Salomon and Montchié (fig. 1). It was probably emitted by the NE crater of Montchié. Tephra des Chaves has been recognized in only one place, as a pluridecimetric unit, between Puy Filhu and Puy Balmet (fig. 1) (Miallier et al., 2008). It has been deposited by surges, oriented S-N, which produced small U-shaped channels in the ground. Its polygenic composition indicates the opening phase of a vent. Its unknown origin might be a small crater that must be located in the close vicinity of the site, where the tephra was discovered. Other orphan tephra layers are locally intercalated between the identified ones (tab. 1), without playing a role in the establishment of the relative chronology. Assessed chronostratigraphy Cho/Par Cho/Par Cho/Par Cho/Par Cho/Par Cha/Cho/Par/Com Cho/Sar Kil/Par Par/X3/Com Par/Com Par/Com VK/Trn/Com/AC Vas/Trn/Bar Kil/ X4/Trn VK/Trn Kil/PdD Kil/PdD Kil/PdD Kil/Pou/Par Kil/ X1/Pou/Par Par/ X2/Clz Par/ X2/Aum Par/PdD Par/PdD VaL/Vas 3.1 - UPDATED TEPHROSTRATIGRAPHIC PATTERNS In the Chaîne des Puys, it is not possible to follow continuously the ejecta of a volcano because the landscape is largely covered by moors, meadows and woods. Most of the outcrops which have provided valuable information are distributed haphazardly by occasional excavations or natural accidents. Several volcanoes gave quasi-identical pyroclastites, for example Vasset and Kilian, while some others emitted sequentially different lavas during eruptions, such as Nugère and Pariou. These difficulties induced errors and hesitations in establishing the chronology, since the pioneer works of e.g., Brousse et al. (1970) or Camus (1975). In the present work, new field observations completed by laboratory characterization enabled to establish localised logs (tab. 1). Cross combination of those logs resulted in the chronological pattern presented in table 2. However, because the relative chronology between certain volcanoes or tephras remains unknown, it is not yet possible to combine all the data in a single pattern. Coordinates X Y 497518 499147 498134 497832 497824 495012 498565 499257 495310 492767 495119 493912 494130 495545 495214 497098 497267 496646 497287 497577 496850 496977 499117 501893 496700 5072259 5071283 5071987 5071622 5071544 5070204 5073255 5070750 5070893 5069139 5071443 5067851 5064651 5067115 5066501 5068704 5067981 5068920 5069487 5069854 5071168 5070657 5068781 5070100 5063572 Tab. 1: Location of the main logs used for establishing figure 1. The youngest volcano/tephra is the left one. Aum: Aumône; Bar: Puy de Barme; Com: Côme; Cho: Chopine; Cha: Les Chaves tephra; Clz: Clierzou; Kil: Kilian; Par: Pariou; Pou: La Poule; PdD: Puy de Dôme; Sar: Sarcouy; Trn; Terrenoire tephra; Vas: Vasset; VaL: la Vache & Lassolas; VK: Vasset or Kilian (not differentiated). AC: Aumône or Clierzou (not differentiated); Xi: indicates unidentified intermediate tephra layers; X1: strombolian fall of potassic trachy-basalt; X2: fall, polygenic lapilli; X3: strombolian fall of potassic trachy-basalt; X4: trachyandesitic ashes, possibly originated from Montchié. Geographical coordinates are in the UTM (wgs84) system. Tab. 1 : Localisation des principales coupes ayant permis d’établir la figure 1. Les volcans sont indiqués par ordre stratigraphique, le plus récent étant à gauche. Aum : Aumône ; Bar : Puy de Barme ; Com : Côme ; Cho : Chopine ; Cha : téphra des Chaves ; Clz : Clierzou ; Kil : Kilian ; Par : Pariou ; Pou : La Poule ; PdD : Puy de Dôme ; Sar : Sarcouy ; Trn ; téphra de Terrenoire ; Vas : Vasset ; VaL : la Vache & Lassolas ; VK : Vasset ou Kilian (non differenciés). AC : Aumône ou Clierzou (non différenciés) ; Xi : indiquent des téphras intermédiaires non identifiés : X1 : retombée strombolienne de trachy-basalte potassique ; X2 : retombée de lapilli polygéniques, X3 : retombée strombolienne de trachy-basalte potassique ; X4 : cendres trachyandésitiques, peut-être originaires du Montchié. Les coordonnées sont dans le système UTM (wgs84). 1210-126 Mep 4-2012.indd 285 26/11/12 10:06 286 Upper level Lower level Terrenoire tephra Pariou La Poule Chopine Vasset Côme Puy de Dôme Aumône or Clierzou Aumône Clierzou Sarcoui Barme Terrenoire tephra Pariou La Poule Chopine Kilian + + + + Vasset Chaves tephra La Vache Côme + + + + + + + + + + + + + + + + + + Tab. 2: Relative chronology assessed by means of tephrostratigraphy. Sign (+) means that the products of the volcano or the tephra mentioned in the first upper horizontal line have been unambiguously observed covering the ones mentioned on the first left column, either in direct contact or with other tephra layers intercalated in between. The association “Aumône or Clierzou” means that the tephra could not be discriminated between these possible sources. Tab. 2 : Chronologie relative déduite de la téphrostratigraphie. Le signe (+) signifie que les produits du volcan ou le téphra mentionné dans la première ligne horizontale ont été observés sans ambigüité au dessus de ceux de la première colonne à gauche, soit en contact direct, soit avec un niveau intermédiaire entre les deux. L’association « Aumône or Clierzou » signifie que la discrimination entre ces deux sources possible n’a pas pu être faite. Recent progress in tephrostratigraphy can be illustrated by the cases of Pariou and Côme. 3.2 - TEPHROSTRATIGRAPHY OF PUY PARIOU The tephras emitted by Puy Pariou are widespread and quite easily recognizable so that they can be considered as a useful chronological marker (Miallier et al., 2008). Due to initial misinterpretation of field observations, Puy Pariou has long been considered as one of the youngest volcanoes in the centre of the Chaîne des Puys. It is now recognized as being older than the Kilian crater as tephras from the latter are found at the surface of the Pariou deposits and lava flows (Miallier et al., 2004a). After Camus (1975), it has been admitted that the Puy Chopine volcano is older than the Puy Pariou, but no evidence supporting this assumption has been presented. Recent systematic prospection allowed collecting, in various places over the Pariou lava-flows and tephras, trachytic lapilli that could be securely attributed to Chopine. Such attribution is based on the prominent occurrence of green pyroxene and yellow sphene (Montiel, 1997; Vernet & Raynal, 2002). The last mineral is completely absent from the trachytic nodules of Kilian and Vasset, which have the same aspect as the Chopine ones. Two first outcrops showing distal ashes of the Puy de Dôme covered by Pariou lapilli were meanwhile discovered (tab. 1). As a conclusion, the Pariou eruption is now bracketed between both Chopine and Puy de Dôme ones. 4 - NUMERICAL DATING 4.1 - AGE OF PUY PARIOU The assumption about the relative young age of Pariou was also based on a radiocarbon measurement 1210-126 Mep 4-2012.indd 286 of carbonized wood at 8,580 ± 350 BP (Sa 94, Delibrias et al., 1964). This age was seemingly supported by the TL ages of 8.2 ± 1.6 ka (Guérin, 1983) and 8.7 ± 1.8 ka (Raynal et al., 1989). But calibration of the Sa 94 radiocarbon result gives an older age of 9.6 ± 1.0 ka, also compatible with the TL ages within error limits. Meanwhile, eight radiocarbon dates were obtained for carbonized wood sampled in the Chopine products and one for peat embedding the Chopine tephra (compilation in Miallier et al., 2004a). Calibration and averaging of the latter dates by means of a Bayesian approach (see method in Lanos & Dufresne, 2012) resulted in the age of 9.66 ± 0.17 ka for Chopine, compatible with tephrostratigraphy and with the age of Puy Pariou estimated at 9.1 ± 0.8 ka (weighted mean of the three results). 4.2 - AGE OF PUY DE CÔME The age of the Puy de Côme volcano was previously estimated to ca. 14-15 ka on the basis of TL measurements (tab. 3) and field arguments (Boivin et al., 2009). This estimation is confirmed by new results. In the Terrenoire quarry (fig. 1), the Côme deposits overlay a sediment of which the surface was dated by radiocarbon applied to minute carbonized plant remains, to 12,070 ± 220 BP (ANNUA-31428, Gif 50024), that is 14.5 ± 1.0 ka, when calibrated. In the same outcrop, the Côme deposits were covered by the Terrenoire tephra which was dated by red TL of quartz (see method in Pilleyre et al., 1992) to 13.6 ± 1.4 ka. The Terrenoire tephra was also dated by red TL in the Barme quarry at 13.7 ± 1.4 ka. All ages were processed by means of a Bayesian approach including radiocarbon calibration and considering stratigraphic constraints (see method in Lanos, 2004; Lanos & Dufresne, 2012). The final age obtained for the Côme is 13.70 ± 0.88 ka. 26/11/12 17:01 287 Stratigraphy Age Method Material Origin Younger than Côme 13600 ± 1400 13700 ± 1400 11600 ± 1660 15900 ± 3000 12000 ±2000 12070 ± 220 BP 16400 ± 3000 TLQ TLF Tephra (TR) Tephra (TR) lava TLF TLQ TLF Carbonized plant remains lava 17300 ± 4000 TLF lava 13200 ± 2600 TLF lava 13300 ±3500 U/Th lava Côme products Older than Côme TLQ 14 C Montchié Laboratory reference Cler 437 Terrenoire 493912 5067851 Montchié Cler 383 Barme 494130 5064651 Côme Cp 23 Pontgibault 489066 5075539 lava Côme Cp 89 493893 5071225 Tephra Côme Cler 300 Forêt de Souis Vulcania 495645 5073325 Filhu or Grand Suchet Filhu or Grand Suchet Filhu or Grand Suchet Filhu or Grand Suchet Site Coordinates ANNUA31428, Gif 50024 Cp 91 Terrenoire 493912 5067851 Les Gardes 492123 5071150 Cp 92 Mazayes 489034 5070461 Cp 88 Bois d’Epinoux 494034 5069570 La Gardette 889620 5068857 Tab. 3: Age results for Côme, either direct, on the Côme products, or indirect for materials older or younger than Côme. TLQ: TL for quartz grains, measured at Clermont Ferrand; TLF: TL for feldspars, measured by Guérin (1983); U/Th: U-Th method, by Condomines et al. (1982). For the site, see map on figure 1, and Boivin et al. (2009). TR refers to the Terrenoire tephra (see text). Geographical coordinates are in the UTM (wgs84) system. Tab. 3 : Résultats de datations concernant le Côme, soit directes sur les produits du Côme lui-même, soit indirectes sur des produits plus anciens (Older) ou plus récents (Younger). TLQ : TL des grains de quartz, mesurée à Clermont Ferrand ; TLF : TL des feldspaths, mesurée par Guérin (1983) ; U/Th : méthode U-Th, par Condomines et al. (1982). Pour les situations, voir la carte sur la figure 1, et Boivin et al., (2009). TR se réfère au téphra de Terrenoire (voir le texte). Les coordonnées géographiques sont dans le système UTM (wgs84). 5 - COMBINATION OF RELATIVE AND NUMERICAL CHRONOLOGICAL DATA The numerical results may give the relative chronology between two volcanoes independently from field obser- La Vache Volcano or tephra La Vache La Vache Chaves tephra Vasset Kilian La Poule Pariou Puy de Dôme Tn. tephra Côme Aumône or Clierzou Pariou Puy de Dôme Sarcoui Chopine Pariou Puy de Dôme Sarcoui vation when the age gap is large enough compared to the measure uncertainties. Accordingly, table 4 was derived from table 2, by combining numerical and relative chronology. It is not yet possible to display all eruptions in a single column by lack of relative chronology between Age (ka) 8.66 ± 0.32 9.2 ± 1.1 References Boivin et al., 2009 Miallier et al., 2010 9.20 ± 0.36 9.40 ± 0.20 Miallier et al., 2004-a Miallier et al., 2004-a Miallier et al., 2010 9.66 ± 0.17 9.1 ± 0.8 11.04 ± 0.23 12.6 ± 1.0 13.7 ± 1.4 13.7 ± 0.9 Miallier et al., 2010 Miallier et al., 2004-b Tab. 4: Chronology combining measured ages and tephrochronology. Relative chronology in a given column is assessed either by stratigraphy (tab. 2) and/or by the significant gap between measured ages. Unreferenced ages are discussed in the present paper. Uncertainties are quoted at 95 %. For Puy de Dôme, only the main phase was considered (see Miallier et al., 2010). The association “Aumône or Clierzou” means that the tephra could not be discriminated between these possible sources. For Kilian, a new radiocarbon age on carbonised wood of 8,415 ± 40 BP (Ly 15654) was combined with the four given in Miallier et al. (2004a). Tab. 4 : Chronologie combinant datations et téphrochronologie. La chronologie relative dans une colonne est déduite de la stratigraphie (tab. 2) ou d’un écart significatif dans les datations absolues. Les résultats sans référence sont discutés dans le texte. Les âges sont en années réelles, avec une incertitude à 95 %. Pour le Puy de Dôme, seule la phase principale a été prise en compte (voir Miallier et al., 2010). L’association « Aumône or Clierzou » signifie que la discrimination n’a pas pu être faite entre les deux sources possibles. Pour le Kilian, un nouvel âge radiocarbone sur bois carbonisé de 8 415 ± 40 BP (Ly 15654) a été combiné avec les quatre donnés dans Miallier et al. (2004a). 1210-126 Mep 4-2012.indd 287 26/11/12 10:06 288 certain volcanoes, Vasset and Kilian for example. The tephras of these two volcanoes are too similar for being distinguished in the field (Vernet & Raynal, 2002, 2008) and their numerical ages are too close (tab. 4). Chronological data obtained from distal tephra deposits were not considered at this stage, because, as outlined earlier, the correlation is often unsecure. However, no part of the interpretation of the distal observations is in contradiction with the proximal ones. Finally, one of the topics that can be addressed with such results, i.e. looking for cycles (Nowell, 2006), can be illustrated by plotting the number of eruptions with time. This was achieved by compiling all the available results for the Chaîne des Puys and young Cézallier, a small volcanic area located 30 km south of the Chaîne des Puys (tab. 5). The test was made for the last 15 millennia only, because the lack of data for older periods could bias the distribution. The histogram (fig. 2) clearly evidences the termination of a period of active volcanism followed by a completely calm one. 6 - DISCUSSION AND CONCLUSION The past experience has shown that improvement in establishing such a chronology is inherent in a process of trial and error. Among the main sources of uncertainty and error is the identification of tephra layers or even lava-flows, and their attribution to given eruptions or volcanoes. Wrong attributions induced by the similarity of tephras emitted by distinct volcanoes may result in errors in chronology. Also, the Chaîne des Puys was previously considered as a quite simple case because most of the volcanoes are monogenic. But recent observations have demonstrated that the Puy de Dôme construction was terminated by a minor summit eruption delayed by about 2 or 3 centuries, which renders the Puy de Dôme chronology less simple (Miallier et al., 2010), and it is now suspected that such a scenario also occurred at Grand Sarcoui. Age (ka) 5-4 6-5 Fig. 2: Distribution of eruptions in both Chaîne des Puys and Cézallier for about 15 ky. Dark grey: assessed; light grey: to be confirmed. Data in table 5. Fig. 2 : Distribution des éruptions de la Chaîne des Puys et du Cézallier depuis environ 15 ka. En gris foncé : bien attestées ; en gris-clair : encore énigmatiques. Données du tableau 5. Eruptions (Fung ?) (Sarliève ?, Beaunit ?) Total (1) (2) References Camus, 1975 Fourmont et al., 2006 ; Juvigné & Stach-Czerniak, 1998 1 3 Boivin et al., 2009 Boivin et al., 2009 1 5 (6) Boivin et al., 2009 12 - 11 13 - 12 Pavin Montchal, Montcineyre, Estivadoux La Vache/Lassolas Chaves, Vasset, Kilian, Poule, Chopine (Mey) Pariou, Puy de Dôme 2, (Sarcoui 2 ?) Puy de Dôme Sarcoui, CF2, CF3 (Barme ?) 1 3 (4) 14 - 13 15 - 14 Nugère, Terrenoire Côme, Tartaret 2 2 7-6 8-7 9-8 10 - 9 11 - 10 2 (3) Vernet & Raynal, 2000 ; Guérin, 1983. Miallier et al., 1994 Tab. 5: Number of eruptions per millenium in the Chaîne des Puys and Cézallier. Names and figures in brackets indicate still enigmatic results. References concern only eruptions not cited in the text. Tab. 5 : Nombre d’éruptions par millénaire dans la Chaîne des Puys et le Cézallier. Les noms et les nombres entre parenthèses indiquent des questions non complètement élucidées. Les références ne concernent que les éruptions non citées dans le texte. It should also be outlined that several volcanoes not mentioned here certainly belong to the same period, including major ones like La Nugère volcano, NE of the Chaîne des Puys, whose eruptive development was complex with a chronology, around 13 ka, remaining uncertain (Vernet & Raynal, 2000; Boivin et al., 2009; Vernet & Raynal, 2012). 1210-126 Mep 4-2012.indd 288 This is an issue for the interpretation of Upper Pleistocene and Holocene volcanic activity in the French Massif Central. 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