# Developing and expanding the Late-Glacial and Holocene tephrochronological framework of France: A new contribution from the Chaîne des Puys volcanic field in the Massif Central

Gwénolé Jouannic, Anne-Véronique Walter-Simonnet, Gilles Bossuet, Pierre Boivin, Hervé Cubizolle, Eric Delabrousse, Anne-Lise Develle, Jean-Luc Devidal, Christine Oberlin, Béatrice Pigny

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Gwénolé Jouannic, Anne-Véronique Walter-Simonnet, Gilles Bossuet, Pierre Boivin, Hervé Cubizolle, et al.. Developing and expanding the Late-Glacial and Holocene tephrochronological framework of France: A new contribution from the Chaîne des Puys volcanic field in the Massif Central. Quaternary International, 2022, 10.1016/j.quaint.2021.12.013. hal-03768032

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Developing and expanding the Late-Glacial and Holocene tephrochronological

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framework of France: A new contribution from the Chaîne des Puys volcanic

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field in the Massif Central

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Gwénolé Jouannic<sup>a,*</sup>, Anne-Véronique Walter-Simonnet<sup>b</sup>, Gilles Bossuet<sup>b</sup>,

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Pierre Boivin<sup>c</sup>, Hervé Cubizolle<sup>d</sup>, Eric Delabrousse<sup>e</sup>, Anne-Lise Develle<sup>f</sup>,

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Jean-Luc Devidal<sup>c</sup>, Christine Oberlin<sup>g</sup>, Béatrice Pigny<sup>e</sup>

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<sup>a</sup> GEOLAB Laboratory, UMR 6042 CNRS, University of Clermont Auvergne, 4

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rue Ledru, F-63000 Clermont-Ferrand, France

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<sup>b</sup> Chrono-Environnement Laboratory, UMR 6249 CNRS, University of

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Bourgogne Franche-Comté, 16 route de Gray, F-25030 Besançon cedex, France

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<sup>c</sup> Magmas and Volcanoes Laboratory, CNRS, IRD, OPGC, University of

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Clermont Auvergne, 6 avenue Blaise Pascal, F-63170 Aubière, France

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<sup>d</sup> Environment City Society ISTHME Laboratory, UMR 5600 CNRS, University

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of Lyon 1, 6 rue Basse des Rives, F-42023 Saint-Etienne cedex 2, France

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<sup>e</sup> Nanomedecine, Imagery Therapeutics Laboratory, EA 4662, University of

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Bourgogne-Franche-Comté and Regional University Hospital of Besançon, 16

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route de Gray, F-25030 Besançon cedex, France

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<sup>f</sup> Laboratory of Environments, Dynamics and Mountain Territories EDYTEM,

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UMR 5204 CNRS, University of Savoie Mont Blanc, Bâtiment « Pôle

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Montagne », 5 boulevard de la mer Caspienne, F-73376 Le Bourget du Lac

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cedex, France

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<sup>g</sup> Radiocarbon Dating Center, University of Claude Bernard Lyon 1, Campus la

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Doua, Bâtiment Carbone 14, 40 Boulevard Niels Bohr, 69622 Villeurbanne,

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France

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27 * Corresponding author.

28 E-mail address: gwenole.jouannic@gmail.com (G. Jouannic).

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30 Abstract

31 The aim of this paper is to highlight new occurrences of tephra and cryptotephra
32 layers from three peatbogs located southeastern from the French Massif Central
33 in France. These tephras were evidenced using magnetic susceptibility logging,
34 scanner imagery and chemical analyses by X-Ray Fluorescence, and
35 characterized by their glass chemistry. Originated from the Chaîne des Puys
36 volcanic field, these six new tephras allow for the definition of a more detailed
37 regional tephrostratigraphic framework. Most of these tephras were deposited
38 between ca. 13,500 and 9,500 yrs cal. BP, and the last one was deposited
39 between 6,400 and 5,920 yrs cal. BP. Some tephras of this framework were
40 previously described in the Jura Mountains, the Northern Alps and the Western
41 Swiss Plateau, and allow its correlation to the Northern European context
42 established by previous studies.

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44 Keywords

45 Tephras; Trachytes; Rhyolites; Nugère; Western Europe

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47 1. Introduction

48 Building a tephrostratigraphic framework in a geographical area extending from
49 Austria to Eastern France became one of the priorities of the group INTIMATE
50 (INTEGRATION of Ice core, MARINE and TERRESTRIAL records of the
51 Last Termination) to efficiently correlate sedimentary sequences on whole
Europe (e.g. Lowe et al., 2001; Davies et al., 2005; Blockley et al., 2014; Lane et al., 2015; Lowe et al., 2017).

Today, correlation of Late-Glacial and Holocene tephrostratigraphical frameworks from northern and southern Europe remains rather awkward because only a few tephras were observed really far from their source volcanoes. The Napolitean Yellow Tuff (NYT, Campi Flegrei Volcanic Zone, Southern Italy) was found in Germany, Austria and Slovenia (Schmidt et al., 2002; Lane et al., 2011a, 2015), the Laacher See Tephra (LST, East Eifel region, West Germany) and the Vedde Ash (VA, Katla volcano, Iceland) were described respectively in northern and north-western Italy and in Slovenia (Finsinger et al., 2008; Lane et al., 2011a). In Western Europe, the Chaîne des Puys volcanic field in the Massif Central (France), of which the volcanic activity ended about 5000 years ago (Boivin et al., 2017) is ideally located between northern and southern Europe. Tephras issued during its Late-Glacial and Holocene activity are therefore likely to have been deposited in key sites that can be used in a European global tephrochronological framework. Moreover, the regime of the stratospheric winds and some tephrostratigraphical studies conducted in Switzerland, in the Vosges and Jura Mountains, and in the northwestern Alps (Juvigné, 1991; Martini, 1970; Walter-Simonnet et al., 2008; Lane et al., 2011b; Jouannic et al., 2015) let to think that at least a part of volcanic ashes coming from eruptions of the Chaîne des Puys volcanic field may have scattered eastwards. But the lack of tephrostratigraphical studies in sites located between the Chaîne des Puys volcanic field and eastern France (Vosges and Jura mountains), Switzerland and the Alps, and the absence of chemical analyses on glass shards in proximal tephras, which prevent their pertinent comparison with distal data that were obtained exclusively on glass shards, leave a doubt over the origin of distal cryptotephras attributed to the Chaîne des Puys volcanic field in distal studies.
The volcanic activity of the Chaîne des Puys volcanic field is chronologically and chemically well known thanks to many studies conducted for forty years on proximal deposits observed near the Chaîne des Puys volcanic field and the Limagne plain (Baudry and Camus, 1972; Juvigné, 1987; Bastin et al., 1990; Juvigné, 1991; Juvigné et al., 1992; Vernet, 1992; Vernet et al., 1998; Vernet and Raynal, 2000 ; Miallier et al., 2004 ; Fourmont et al., 2006 ; Vernet and Raynal, 2008 ; Boivin et al., 2017). The Chaîne des Puys volcanic field results from the last activity period in the volcanic history of the French Massif Central which began 65 Ma ago (Nehlig et al., 2003). These activity periods ranged from 156,000 to 7,000 years cal. BP and resulted in the formation of more than 110 volcanoes, arranged along a north-south axis. The Chaîne des Puys volcanic field is essentially made up of slag cones, associated with flows as well as various eruptive structures (e.g. maars, domes, protrusions). Geochemical and chronological data show a global evolution with four main eruptive periods characterized by increasingly differentiated lava flows and separated by rest phases.

However, to our knowledge, the dispersion of tephras of the Chaîne des Puys volcanic field eastwards, beyond the Limagne plain, and southwards, beyond the Mont-Dore Massif, are limited. In proximal sites studied around the Chaîne des Puys volcanic field, the chemical composition of volcanic deposits was always obtained either on the bulk deposit or on phenocrysts, because the volcanic glasses are not very frequent and often mineralised when present. In the Clermont-Ferrand basin, 43 ash layers dated to between 150 and 80 ky and 75 ash layers between 80 and 40 ky have been observed. Six other Holocene tephra layers have already been found in the same area (Vernet, 1992). In the Monts du Forez, around 90 km southwards from the Chaîne des Puys volcanic field, Etlicher et al. (1987) described a tephra correlated with the Puy de la Nugère volcano which is the only certain eastern distal occurrence of a tephra coming from the Chaîne des Puys volcanic field.
Because of the occurrence of two tephras originating from the Chaîne des Puys volcanic field and correlated with eruptions of the Puy de la Nugère and Puy Vasset volcanoes in several lakes of Jura Mountains and Switzerland (Walter-Simonnet et al., 2008; Lane et al., 2011b; Jouannic et al., 2015) we decided to prospect peat bogs located between the Chaîne des Puys volcanic field and the Jura Mountains and the Alps in order to try to identify them and to remove the doubt which remains on their origin. Peat bogs with, at least partly, Late-Glacial infillings are not very frequent eastwards from the Chaîne des Puys volcanic field. The three sites we present here were chosen according to palynological and chronological studies conducted for several years on these sites (Cubizolle et al., 2012).

## 2. Regional and local settings

### 2.1. The Gourgon and Molhiac peat bogs.

The Gourgon and Molhiac peat bogs are located in the Monts du Forez (Figure 1), a plutonic and metamorphic massif from the eastern French Massif Central which culminates at 1634 m a.s.l.. The relief is, by places, undulating with valley floors that can be under 500 m a.s.l.. The main morphologies are inherited from previous glacial periods. Moraines and fluvio-glacial deposits were formed during a glaciation which probably started during the colder periods of the Quaternary and continued during the Würmian Ice Age to end about 11,700 years ago. Only the highest zones of the Forez area, with altitudes higher than 1350 m a.s.l., like the Gourgon site, present some rare morainic deposits and a glacial relief (Etlicher, 1986, 2005; Etlicher et al., 1987; Cubizolle et al., 2014).

The peaty system of Gourgon is part of a wide peatland system with a surface of about 88 hectares (Porteret, 2008). The cores were recovered in the rounded highest part of the peat bog (45°36′31.62" N, 3°52′59.75" E, 1367 m a.s.l.). The coring site was chosen based on many datations conducted on the whole peatland system (Argant and Cubizolle, 2005; Porteret, 2008; Cubizolle and
Argant, 2006). Moreover, the chronology of sedimentation is well known thanks to palynological analyses and radiocarbon datations. The peaty sedimentation recovered an organic rich coarse sand dated from the middle of the Allerød (13,359–13,095 yrs cal. BP; Porteret, 2008; Cubizolle et al., 2014) with a peat growth beginning during the Preboreal (11,335–11,175 yrs cal. BP).

The Molhiac peat bog (45°30′09″ N, 3°51′20″ E, 1130 m a.s.l.) is an ombrotrophic peat bog slightly rounded, with surface of about 3 hectares, situated upstream of the Valley of Ligonne. The extension dynamics of the peat bog was modelized by Cubizolle et al. (2015) according to 31 sediment cores. The peaty sedimentation started during the Allerød, about 13391–13091 yrs cal. BP, by covering an organo-mineral facies (Cubizolle et al., 2015). Our coring site was chosen according to this study.

## 2.2. The Digonnière peat bog

On the other hand, the Digonnière peat bog developed in the Massif du Pilat, about 40 km south-eastwards from the Monts du Forez (Figure 1). The Massif du Pilat (1432 m a.s.l.) is composed of two main geological areas: a granitic one, and a micaschist and gneissic one (Ledru et al., 2001; Faure et al., 2009). During the last glaciation, rocky screes, which extended over more than one kilometre, developed above 900 m of altitude on the northern mountainsides.

The Digonnière peat bog (45°20′51.8″ N, 4°28′36.9″ E, 1055 m a.s.l.) is, as those of Molhiac and Gourgon, a rounded peat bog and covers a 10 hectares area. Although younger than the Gourgon and Molhiac peat bogs, it is one of the oldest peat bogs of the Massif du Pilat. The peaty sedimentation started about 9725 yrs cal. BP ago and covered sands and gravels (Cubizolle et al., 2004; Argant and Cubizolle, 2005; Cubizolle et al., 2012).
164 3. Material and methods

165 The cores presented here were taken using a Russian corer providing split cores
166 1 m long with a diameter of 8 cm.

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168 3.1. Cryptotephras investigations

169 Cryptotephras were detected using split core magnetic susceptibility logging and
170 chemical analyses by X-Ray Fluorescence (XRF). These latter methods are
171 frequently used for the detection of volcanic ash layers (Sandgren and Snowball,
172 2001; Vannière et al., 2004; Walter-Simonnet et al., 2008; Kylander et al., 2012;
173 Damaschke et al., 2013; Wulf et al., 2013; Jouannic et al., 2014, 2015, 2016).
174 Here, we only present titanium, potassium and zirconium analyses, as the other
175 elements do not show any specific variations.

176 Magnetic susceptibility was measured on split cores with the point sensor MS2-
177 E1, a high-resolution surface scanning sensor from Bartington Instruments.
178 Measurements were made at 0.5 cm intervals. X-Ray Fluorescence analyses
179 were also performed at the same interval in the EDYTEM Laboratory
180 (University of Savoie Mont Blanc, France) (operating conditions: voltage of 10
181 and 30 KeV, 750 mA beam current, opening of 15 mm and counting time of 45 s
182 for 10 KeV and of 30 s for 30 KeV).

183 Three-dimensional medical imagery (scanner) was performed in Besançon,
184 France (Regional University Hospital of Besançon) with a resolution of 500 µm
185 in order to test it for tephra detection. Scanning allows showing sedimentary
186 structures in fine cuts in all directions of the space. The occurrence of a
187 significant contrast of density between the volcanic deposit and the host
188 sediment is the principle of detection on which this method is based. The
189 effectiveness of this detection method will be better in peat due to the very weak
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density of the organic matter in comparison with mineral constituents of the
 tephras.

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3.2. Geochemical characterization of tephras

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Tephra samples were wet sieved and separated into a 45 µm fraction. The >45 µm fraction was treated with a 10% solution of H2O2 to remove organic material and with a 10% solution of acetic acid during 30 minutes to remove carbonates. Particles were separated using the density separation method to isolate glass shards from phenocrysts (Turney, 1998; Blockley et al., 2005). This separation was carried out with densities of 2 and 2.55, with the interval corresponding to the density of glass shards. Electron probe microanalyses (EPMA) of glasses were obtained on a WDS Cameca SX100 at the “Magmas and Volcanoes Laboratory (LMV)”, University of Clermont Auvergne. The instrument was calibrated on natural glass (A99). The analytic conditions are similar to standard analysis (Óladóttir et al., 2011): 15 kV accelerating voltage and 4 nA beam current to reduce Na loss and 4 µm beam diameter, in agreement with Hunt and Hill (2001) and Kuehn et al. (2011). Counting time was 10 s for Na, Ca, Ti and Si; 20 s for Mg and Al; 30 s for Mn and finally 40 s for Fe and K.

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3.3. Age of the tephras

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The chronology of the Gourgon and Digonnière sedimentary sequences are well constrained according to pollen analyses and radiocarbon dates carried out in previous studies (Reille et al, 1992; Argant and Cubizolle, 2005; Porteret, 2008; Cubizolle and Argant, 2006; Cubizolle et al., 2012, 2014; Jouannic et al., 2014). In order to correlate our cores with these previous cores and to date the tephras, new dates were carried out as part of this study: six for Gourgon, and two for the Digonnière sequence. On the other hand, the chronology of the Molhiac bog

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appears to be much less constrained (Cubizolle et al., 2012, 2015). Three

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radiocarbon dates were performed on our Molhiac core as part of our study.

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When possible, we sampled the peat containing the tephra layers. The 11 peat

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samples were prepared for AMS radiocarbon dating and carried out in the

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Radiocarbon Dating Laboratory, University of Lyon (France), in the Poznan

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Radiocarbon Laboratory (Poland), or at Beta Analytic (USA), in order to

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determine the age of the volcanic deposits. The 14C ages were calibrated using

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the IntCal20 calibration curve after Reimer et al. (2020) and the CALIB 8.2

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software (Stuiver et al., 2021).

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## 4. Results

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On the basis of the peaks of the magnetic susceptibility, titanium, zirconium,

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and potassium, used for the tephra identifications as in Jouannic et al. (2015),

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and on scanner pictures, eleven levels of tephras were identified and

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characterized: six in Gourgon (tephras MF1 and G2 to G6, Figure 2), two in

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Digonnière (tephras D1 and D2, Figure 3) and three in Molhiac (tephras MF1,

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M2 and M3, Figure 4). The MF1 tephra was already characterized in a previous

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publication (Jouannic et al., 2014).

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### 4.1. Chemical composition of the tephras

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The chemical composition of the volcanic glass shards from the tephras from the

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Gourgon, Digonnière and Molhiac peat bogs is similar to the chemical

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composition of the volcanic products of the Chaîne des Puys volcanic field

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(Tables 2 and 3, Figure 6A to F). However, this should be considered with

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reserve since the chemical composition of the lava in the Chaîne des Puys

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volcanic field was obtained by analysing the total rock (Boivin et al., 2017),
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which may differ significantly from the chemical composition of volcanic glass.

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Nevertheless, the chemical compositions of tephras presented in Figure 6 range from trachybasaltes to rhyolites, and, with the exception of tephras MF1 and D1, greatly differ from the chemical compositions of contemporary tephras but of different origins, such as the Laacher See Tephra, the main Late-Glacial volcanic eruption in the Eifel Massif (Germany) and of phonolytic composition, and tephras resulting from Icelandic volcanic activity.

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## 4.2. Tephrostratigraphy and correlations with volcanoes and poximal tephras

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The figures 5 and 6 show the chemical and chronological correlations for the tephras investigated at the Gourgon, Digonnière and Molhiac peat bogs we used to build the tephrostratigraphy described below.

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### 4.2.1. The G6 tephra

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G6, the oldest tephra in our sediment cores, was only found at Gourgon. It shows a trachyandesitic composition (Figures 6 and 7, Table 2) and is dated to 13,449–13,184 years cal. BP (Figure 5, Table 1). These chemical and chronological criteria allow its correlation with the eruption of the Puy de la Nugère volcano which was dated to between 13,000 and 14,000 years cal. BP from the subjacent palaeosoil and organic fragments sampled within the tephra in the plain of Limagne (Vernet and Raynal, 2000; Vernet, 2013; Boivin et al., 2017). Other datations, obtained via radiocarbon, thermoluminescence and palynological correlations, performed on sites north of Limagne, point out to a medium age of about 13,700 ± 400 years cal. BP for the Nugère tephra (also named CF1; Vernet et al., 1990; Vernet and Paquereau, 1991).

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### 4.2.2. The G5 tephra
This very homogeneous trachytic tephra (Figure 6, Table 2), only observed in Gourgon, is a millimetric layer (4–5 mm) dated to 13,342 – 13,179 years cal. BP (Figure 5, Table 1). The trachytic activity of the Chaîne des Puys volcanic field mainly occurred between 9,000 and 11,000 years (Boivin et al., 2017). The building up of the Puy Sarcoui volcano is the only oldest volcanic trachytic demonstration which occured 12.6 ± 1.0 kyrs ago (Miallier et al., 2003). G5 tephra correlates with the Puy Sarcoui volcano activity, but the Puy Sarcoui volcano is described as a cumulo-dome (Miallier et al., 2017) which grew calmly after an initial explosive phase whose age is 10.4 ± 1.0 kyrs. Traces of this phase are noticed some kilometres east of the dome, but no tephra is presently correlated to this volcano in Limagne.

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### 4.2.3. The G4 tephra

G4 was again only observed in Gourgon. This basaltic-trachy-andesitic to phonotephritic tephra is 1 cm in thickness and dated to 12,453 – 11,817 years cal. BP (Figures 5 and 6, Tables 1 and 2). Its chemical composition partly correlates with the CF3 and CF4 tephras described by Vernet and Raynal (2002), which are trachybasaltic and trachy-andesitic, and whose respective ages are 12,500 and 11,400 years (Boivin et al., 2017). Vernet (2011) proposed that the CF4 tephra was emitted by the Puy de Pariou volcano dated to 10,000 years cal. BP. The chemical compositions of lavas from the Puy de Pariou volcano are trachytic to basaltic trachyandesite (Boivin et al., 2017; Miallier et al., 2012). Another known eruption with close trachy-basaltic composition is that of the Puy de Barme volcano dated to 11,900 ± 1,200 years cal. BP (Guerin, 1983), but no tephra was described related to this eruption. The Puy de Pariou volcano is the most probable source for the G4 and CF4 tephras.

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### 4.2.4. The G3-M3 tephra
As shown in figures 6 and 7, G3 and M3 represent a same trachytic tephra (Table 2), which is characterised by a rather important thickness (from 3 to 4 cm). According to the age-depth model obtained in Gourgon, the age of this tephra is about 10,900 years cal. BP and correlates with available datations in Molhiac (Figure 5). So we call this tephra MF2 (Mont du Forez #2). Three trachytic eruptions could have caused this tephra: the eruption of Puy de Dôme volcano, dated to $10.7 \pm 0.1$ kyrs (Condomines, 1997) whose 3 pyroclastic layers with important lateral variations of thickness (5 to 120 cm) are described by Miallier et al. (2010), the one of the Puy Grand Sarcoui volcano dated to $10.4 \pm 0.1$ kyrs (Boivin et al., 2017) and the one of the Puy Chopine volcano, dated to $9.7 \pm 0.2$ kyrs (Vernet and Raynal, 2000). No tephra originating from the Puy de Dôme volcano or Grand Sarcoui volcano were mentioned in tephrostratigraphic studies conducted around the town of Clermont-Ferrand and in the Limagne region. On the other hand, eruptive products of the Puy Chopine volcano are known. For example, the sedimentological sequence of Marsat, located west of the plain of Limagne, contains the different stages of the Puy Chopine volcanic eruptions with metric lahars and ash layers (Vernet and Raynal, 2008). Trachytic products of the Puy Chopine volcano are characterised by a high content of $SiO_2$ (up to 70 %), which is higher than the one noticed in the trachyte of the Puy de Dôme volcano (Foury, 1983; Boivin et al., 2017). These criteria are more in agreement with the hypothesis of the Puy Chopine volcano as the source volcano for the G3-M3 tephra (Figure 7). These tephra may eventually be the result of an unknown early stage of activity of the Puy Chopine volcano.

### 4.2.5. The G2-M2 tephra

These two tephras have a similar trachytic composition, marked by a heterogeneous content of silica (Figures 6 and 7, Table 2). In Gourgon, this tephra is dated to 10,372–10,201 years cal. BP, which is consistent with the
available datations in Molhiac. So we call this tephra MF2 (Mont du Forez #2).

The age of G2-M2 tephra is closer to those of the trachytic eruptions of the Puy
Chopine volcano (9.7 ± 0.2 kyrs; Miallier et al., 2012) and the Puy Grand
Sarcoui volcano (10.4 ± 0.1 kyrs; Miallier et al. (2017) which emitted lavas with
similar compositions, too (Figure 7). Presently, it seems difficult to relate G2-
M2 to a precise volcano.

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334 4.2.6. Tephra D2

This trachytic tephra, dated to 9,597–9,487 years cal. BP (Figure 5, Table 1) has a very homogeneous chemical composition compared to previous trachytic tephras observed in Gourgon and Molhiac (Figures 6 and 7, Table 2). This age is close to the age of the Kilian volcano, 9,500 years cal. BP, (Boivin et al., 2017) and close to the age of the Marsat Formation (9,540 ± 150 years cal. BP) described in Limagne (Vernet et al., 2001), but the SiO₂ and alcali contents of the G2-M2 are lower (Figure 7). On the other hand, the tephras D2, CF5 and of the Marsat Formation have close compositions. CF5 is described in Limagne but, presently, its source volcano remains unknown (Boivin et al., 2017).

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345 4.2.7. The MF1 tephra

Tephras FM1 and D1 are similar (Figures 5, 6 and 7, table 2), but D1 correspond
to the less differenciated glasses of the MF1, as if there was a sorting with
distance from the source volcano or a magmatic evolution during the eruption.
FM1 and D1 correspond to the youngest tephras present in our cores and are the
only ones with a rhyolitic composition. Peat containing this tephra was dated in
Molhiac and Digonnière (Figure 5). The obtained ages are not exactly similar
and give an age of 6,396–5,920 yrs cal. BP (Table 1 and Figure 5). This tephra is
therefore contemporary of volcanic activities of the volcanoes Montchal (about
354 6,900 yrs cal. BP), Montcineyre (6,920 ± 150 yrs cal. BP), and Pavin (6,700 ±
355 110 yrs cal. BP), located in the southern part of the Chaîne des Puys volcanic
356 field, but these volcanoes are characterised by basaltic and trachy-andesitic
357 products (Villemant et al., 2016; Juvigné and Miallier, 2016; Boivin et al.,
358 2017). The analysis of trace elements is in agreement with a local volcanic
359 origin but the source volcano remains presently unknown (Jouannic et al., 2014).

360 Although never observed in the Holocene volcanism of the Massif Central, the
361 rhyolitic composition of this tephra is not in disagreement with the magmatic
362 evolution of the Chaîne des Puys volcanic field because the degree of
363 differentiation of lava evolved with time (Boivin et al., 2017). Indeed, the
364 activity of the Chaîne des Puys volcanic field started with basaltic eruptions
365 evolving little by little towards a trachyandesitic, then trachytic composition.

366

367 5. Discussion

368 5.1. Trachytic tephras

369 Apart from the tephras MF1, G4 and G6, the tephrostratigraphical framework
370 built for the Monts du Forez Mountains and Massif du Pilat is composed of
371 trachytic tephras which compositions are very close (Figure 6). Without exact
372 datation, these tephra layers are chemically very difficult to distinguish.

373 Nonetheless, building a Principal Component Analysis (PCA) with all their
374 chemical characteristics (major elements) makes it clearly possible to
375 distinguish them from one each other (Figure 8). The PCA also shows that
376 tephra G2-M2 is very dispersed, in both sites. This particularity may be a
377 consequence of magmas mixing or magma evolution during the eruption. On the
378 other hand, the tephras G5, G3-M3 and D2 are characterised by homogeneous
379 and distinct compositions. Their identification and distinction is then possible if
380 using all their chemical characteristics.
382 5.2. Correlation with distal tephras

383 Among the seven tephras observed in our cores, some of them may be correlated
384 to proximal tephras and/or to distal tephras.

385 The tephra G6 is also mentioned under the name of Nugère tephra in several
386 lake fillings in the Jura Mountains (Walter-Simonnet et al., 2008; Jouannic et al.,
387 2015) where it just precedes the Laacher See Tephra, which has recently been
388 dated to 13,006 years cal. BP (Reinig et al., 2021) whereas previous studies
389 dated it to about 12,900 years cal. BP (Hajdas et al., 1995; Brauer et al., 1999;
390 Friedrich et al., 2004). In the Lake Lautrey (Jura Mountains) the Nugère tephra
391 is observed as two successive thin layers dated to about 13,300 years cal. BP.
392 Their volcanic glass shards were too altered to be analyzed (Walter-Simonnet et
393 al., 2008) so it's impossible to correlate the tephra G5 with one of the two tephra
394 layers observed in this lake.

395 On figure 7, the chemical composition of the tephra MF2 is close to the one of
396 the tephra Val12-374.5 / Sop-T4.74 described in Lake Val (Jura Mountains) and
397 Lake Soppensee (Switzerland), dated to 9,336 ± 71 years cal. BP in the latter
398 (Lane et al., 2011b; Jouannic et al., 2015) and related to the Puy Vasset or Puy
399 Kilian volcanos. Nonetheless, even if chemical compositions are quite similar,
400 respective ages of the tephras MF2 and Val12-374.5 / Sop-T4.74 are too
401 different to be the same tephra.

402 On the other hand, the ages of the tephra D2 and Val12-374.5 / Sop-T4.74 are
403 close (9,336 ± 71 years cal. BP for Val12-374.5 / Sop-T4.74 in Lake Soppensee;
404 Lane et al., 2011b), but the SiO2 and alcali contents of D2 are lower (Figure 7).
405 However, the tephra Val12-374.5 / Sop-T4.74 is related to the Puy Vasset or
406 Puy Kilian volcanos, which eruptions were dated to 9.2 ± 0.4 kyrs for the Puy
407 Vasset volcano (Miallier et al., 2012) and to 9.4 ± 0.2 kyrs for the Puy Kilian
408 volcano (Miallier et al., 2004, 2012). These eruptions followed an eruption of
409 the Puy Chopine volcano dated to 9.7 ± 0.2 kyrs by Miallier et al. (2012). Due to
410

the very close ages and chemical characteristics of their products, it remains

411

presently very difficult to distinguish them from one each other (Boivin et al.,

412

2015, 2017). Nonetheless, the tephras D2, CF5, Marsat and Val12-374.5 / Sop-

413

T4.74 are probably related to a same eruption.

414

415

## 6. Conclusions

416

The tephra layers identified in the peat bogs of Molhiac, Gourgon and

417

Digonnière constitute important chronological markers for sites located to the

418

east and southeast of the Chaîne des Puys volcanic field, completing the

419

chronological data got by palynological correlations or by radiocarbon dates

420

(Table 3). Today, the source volcanoes of some of these tephras remain

421

unknown, but our results bring new information on the recent volcanic activity

422

and the chemical evolution and variety of volcanism of the Chaîne des Puys

423

volcanic field. Our study also precise the dispersion of tephras emitted by

424

volcanoes of the Chaîne des Puys volcanic field. For the moment, some of these

425

new tephras may be correlate only to tephras identified close to the town of

426

Clermont-Ferrand and in the Limagne region (Figure 9), but three of them

427

(Nugère, Vasset-Kilian and MF1 tephras) were previously identified in the Jura

428

Mountains, in the Northern Alps, and on the Western Swiss Plateau (Figure 10).

429

Our data confirm their origin and allow building a tephrostratigraphical

430

framework for the east and southeast of the Chaîne des Puys volcanic field

431

which allows correlations to the Northern European context established by

432

previous studies (Turney et al., 1997; 2004; Lowe, 2001; Davies et al., 2002;

433

Wastegård, 2005; Walter-Simonnet et al., 2008; Lane et al., 2011b, 2012, 2015;

434

Wulf et al., 2013; Jouannic et al., 2015).

435

436
437 Author contributions

438 Gwénolé Jouannic: Conceptualization, Funding acquisition, Methodology, Data

439 collection, analysis and interpretation. Anne-Véronique Walter-Simonnet:

440 Conceptualization, Funding acquisition, Methodology, Data collection, analysis
441 and interpretation. Gilles Bossuet: Methodology, analysis and interpretation.

442 Pierre Boivin: analysis and interpretation. Hervé Cubizolle: Conceptualization,

443 Methodology, interpretation; Eric Delabrousse: analysis and interpretation,

444 Anne-Lise Develle: analysis and interpretation. Jean-Luc Devidal: analysis and

445 interpretation. Christine Oberlin: interpretation. Béatrice Pigny: analysis and

446 interpretation. All authors contributed to the Drafting and Critical revision of the
447 article.

448

449 Data availability.

450 Tephra glass major element geochemistry is available in table 2.

451

452 Declaration of competing interest

453 The authors declare that they have no known competing financial interests or

454 personal relationships that could have appeared to influence the work reported in
455 this paper.

456

457 Acknowledgments. We are grateful to the Région Franche-Comté, the Franche-

458 Comté University (BQR funding) and the National Institute for Earth Science

459 and Astronomy (INSU) which supported this work. We would thank two

460 anonymous reviewers for their helpful and constructive remarks to improve the
461 manuscript.

462

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Sandgren, P., Snowball, I., 2001. The Late Weichselian sea level history of the Kullen Peninsula in northwest Skåne, southern Sweden. Boreas 30 (2), 115-130.

722

723

Schmidt, R., van den Bogaard, C., Merkt, J., Müller, J.M., 2002. A new Lateglacial chronostratigraphic tephra marker for the south-eastern Alps: The Neapolitan Yellow Tuff (NYT) in Längsee (Austria) in the context of a regional biostratigraphy and palaeoclimate. Quaternary International 88 (1), 45-56.

724

725

726

727

728

Schnellmann, M., Anselmetti, F.S., Giardini, D., McKenzie, J.A., 2006. 15,000 years of mass-movement history in Lake Lucerne: Implications for seismic and tsunami hazard: Eclogae Geologicae Helvetiae 99, 409-428.

729

730

731

Stuiver, M., Reimer, P.J., Reimer, R.W., 2021. CALIB 8.2 [WWW program] at http://calib.org, accessed 2021-11-30
732

Turney, C.S.M., 1998. Extraction of rhyolitic component of Vedde microtephra from minerogenic lake sediments. Journal of Paleolimnology 19, 199–206.

733

734

Turney, C.S.M., Harkness, D.D., Lowe, J.J., 1997. The use of microtephra horizons to correlate Late-glacial lake sediment successions in Scotland. Journal of Quaternary Science 12 (6), 525–531.

735

736

737

Turney, C.S.M., Lowe, J.J., Davies, S.M., Hall, V., Lowe, D.J., Wastegård, S., Hoek, W.Z., Alloway, B., SCOTAV, INTIMATE members, 2004.

738

739

Tephrochronology of Last Termination sequences in Europe: a protocol for improved analytical precision and robust correlation procedures (a joint SCOTAV-INTIMATE proposal). Journal of Quaternary Science 19, 111–120.

740

741

742

Turney, C.S.M., Van den Burg, K., Wastegård, S., Davies, S.M., Whitehouse, N.J., Pilcher, J.R., Callaghan, C., 2006. North European last glacial-interglacial transition (LGIT; 15–9 ka) tephrochronology: extended limits and new events. Journal of Quaternary Science 21, 335–345.

743

744

745

746

van den Bogaard, P., Schmincke, H.-U., 1985. Laacher See Tephra: A widespread isochronous late Quaternary tephra layer in central and northern Europe. Geological Society of America Bulletin 96, 1554–1571.

747

748

749

Vannière, B., Bossuet, G., Walter-Simonnet, A.-V., Ruffaldi, P., Adatte, T., Rossy, M., Magny, M., 2004. High-resolution record of environmental changes and tephrochronological markers of the Last Glacial-Holocene transition at Lake Lautrey (Jura, France). Journal of Quaternary Science 19, 797–808.

750

751

752

753

Vernet, G., 1992. Message du volcanisme regional dans les formations quaternaires de Limagne occidentale (Massif Central Français). Minéraux denses et retombées. Thèse de l'Université de Bordeaux, France (Doctotal Thesis).

754

755

756

757

Vernet, G., 2011. Les dépôts pyroclastiques distaux: caractérisation, établissement de téphrostratigraphies de référence, taphonomie et relations

758
759 homme/volcan. Mémoire d'Habilitation à Diriger des Recherches, Université
760 Blaise Pascal, Clermont-Ferrand, 584 p. (Habilitation Thesis).

761 Vernet, G., 2013. La séquence sédimentaire des Gravanches/Gerzat: enregistrement d'évènements catastrophiques à valeur chronologique en Limagne d'Auvergne (Massif Central, France). Quaternaire 24 (2), 109-127

764 Vernet, G., Paquereau, M.-M., 1991. Le cours moyen de la Morge et de ses affluents (Puy-de-Dôme, France) au Pléistocène: éléments de chronologie et de paléoenvironnement. Cahiers du Quaternaire 16, 431-449.

767 Vernet, G., Raynal, J.-P., 1995. La Tephra des Roches, marqueur du volcanisme contemporain de la fin du Magdalénien dans le Massif Central français.

769 Comptes rendus hebdomadaires des séances de l'Académie des Sciences 321, série IIa, 713-720.

771 Vernet, G., Raynal, J.-P., 2000. Un cadre téphrostratigraphique réactualisé pour la préhistoire tardiglaciaire et holocène de Limagne (Massif central, France).

773 Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science 330, 399-405.

775 Vernet, G., Raynal, J.-P., 2002. Éruptions trachytiques de la Chaîne des Puys (France) et leurs impacts sur les environnements. In: Raynal, J.-P., Albore-Livadie, C., Piperno, M. (Eds.), Hommes et volcans – De l'éruption à l'objet. Les Dossiers de l'Archéo-Logis 2, 49-56.

779 Vernet, G., Raynal, J.-P., 2008. The Marsat formation and the CF7 tephra, distal markers of violent trachytic eruption of the Chaine des Puys during the Boreal period. Quaternaire 19, 97-106.

782 Vernet, G., Raynal, J.P., Fain, J., Miallier, D., Montret, M., Pilleyre, T., Sanzelle, S., 1998. Tephrostratigraphy of the last 160 ka in western Limagne (France). Quaternary International 47(8), 139-146.
785 Vernet, G., Raynal, J.-P., Kieffer, G., Camus, G., Guadelli, J.-L., Vivent, D.,
786 Miallier, D., Sanzelle, S., Pilleyre, Th., Fain, J., Montret, T M., 2001. L'éruption
787 trachytique du puy Chopine (Puy-de-Dôme, France): Impacts proximaux et
distaux et implications écoarchéologiques. In: Juvigné, E., Raynal, J.-P. (Eds.),
788 TEPHRAS – chronologie – archéologie. Les dossiers de l'Archéo-Logis 1, 227–
789 234.
790

791 Vernet, G., Raynal, J.P., Miallier, D., Pilleyre, T., Fain, J., Sanzelle, S., Montret, M., 1990. La retombée de la Moutade, marqueur startigraphique de l'Alleröd en Limagne septentrionale (Massif Central, France). Comptes rendus de l'Académie des sciences. Série 2, Mécanique, Physique, Chimie, Sciences de l'univers, Sciences de la Terre 310, 1077-1082.
792
793
794
795

796 Vernet, G., Raynal, J.P., Vivent, D., 1996. La Tephra de la Rue Sous-les-Vignes, marqueur en Limagne du volcanisme trachytique postglaciaire de la Chaîne des Puys. Comptes rendus hebdomadaires des séances de l'Académie des Sciences 323, série IIa, 325-331.
797
798
799

800 Villemant B., Caron B., Thierry P., Boivin P., 2016. Magmatic Evolution of Pavin's Group of Volcanoes: Petrology, Geochemistry and Modeling of Differentiation Processes. A Preliminary Study. In: Sime-Ngando T., Boivin P., Chapron E., Jezequel D., Meybeck M. (Eds.), Lake Pavin. History, Geology, Biogeochemistry and Sedimentology of a Deep Meromictic Maar Lake. Springer Springer, Cham, pp. 135-150.
801
802
803
804
805

806 Walter-Simonnet, A.-V., Bossuet, G., Develle, A.-L., Bégeot, C., Ruffaldi, P., Magny, M., Adatte, T., Rossy, M., Simonnet, J.-P., de Beaulieu, J.-L., Vannière, B., Thivet, M., Millet, L., Regent, B., Wackenheim, C., 2008. Chronologie et spatialisation de retombées de cendres volcaniques tardiglaciaires dans les massifs des Vosges et du Jura, et le plateau suisse. Quaternaire 19 (2), 117-132.
807
808
809
810

811 Wastegård, S., 2005. Late Quaternary tephrochronology of Sweden: a review.
812 Quaternary International 130, 49-62.
813

Wulf, S., Ott, F., Slowinski, M., Noryskiewicz, A.M., Draeger, N., Martin-

814

Puertas, C., Czymzik, M., Neugebauer, I., Dulski, P., Bourne, A.J.,

815

Blaszkiewicz, M., Brauer, A., 2013. Tracing the Laacher See Tephra in the
varved sediment record of the Trzechowskie palaeolake in central Northern
Poland. Quaternary Science Reviews 76, 129–139.

816

817

818

819

Figure captions

820

821

Figure 1: Map of the Massif Central in France showing the location of the

822

Chaîne des Puys Volcanic Field (inlet) and the location of the Gourgon, Molhiac
and Digonnière sites (red stars).

823

824

825

Figure 2: Data from the stratigraphy taken in the Gourgon peat bog, Massif

826

Central (France), with lithology, magnetic susceptibility, scanner pictures,
radiocarbon dates and Ti, K and Zr counts from XRF core scanning. Grey lines
underline tephras and cryptotephras.

827

828

829

830

Figure 3: Data from the stratigraphy taken in the Digonnière peat bog, Massif

831

Central (France), with lithology, magnetic susceptibility, scanner picture, and
radiocarbon dates. Grey lines underline tephras and cryptotephras.

832

833

834

Figure 4: Data from the stratigraphy taken in the Molhiac peat bog, Massif

835

Central (France), with lithology, magnetic susceptibility, scanner pictures,

836

radiocarbon dates, and Ti, K and Zr counts from XRF core scanning. Grey lines
underline tephras and cryptotephras.

837

838
Figure 5: Upper three panels: Age-depth models and calibrated radiocarbon dates (in red) of the 11 tephras (grey bars) detected in Gourgon, Molhiac and Digonnière peat-bogs, Massif Central (France). Lower panel: Summerized dating ranges for the regionally detected tephras.

843

Figure 6: A and B: TAS Diagrams (Le Bas et al. 1986) of chemical composition (major elements) of glass shards of the tephras from the stratigraphies of Gourgon, Molhiac and Digonnière, Massif Central (France). C and D: SiO₂/K₂O diagrams of chemical composition (major elements) of glass shards of tephras from Gourgon, Molhiac and Digonnière compared with Northern Europe volcanic provinces. E and F: SiO₂/CaO diagrams of chemical composition (major elements) of glass shards of tephras from Gourgon, Molhiac and Digonnière compared with Northern Europe volcanic provinces (after data from Maury et al., 1980; Davies et al. 2005; Turney et al. 2006; Finsinger et al. 2008; Boivin et al., 2017; Meara, 2012).

854

Figure 7: Zoom of TAS Diagrams (Le Bas et al. 1986) of chemical composition (major elements) of glass shards of some tephras from the stratigraphies of Gourgon, Molhiac and Digonnière, Massif Central (France), compared to other tephras and lavas. A: G6 tephra; B: G3, M3 and D2 tephras; C: M2, G2 and D2 tephras; D: D2 tephras; E: MF1 and D1 tephras. See text for data references.

860

Figure 8: PCA of trachytic tephras of the Gourgon and Molhiac sites, Massif Central (France).

863
864

Figure 9: Correlation of tephras of the Gourgon, Molhiac and Digonnière sites, Massif Central (France), with tephras identified near the town of Clermont-Ferrand (Boivin et al., 2017).

865

866

867

868

Figure 10: Occurrences of MF1 tephra, Vasset-Kilian tephra, Nugère tephra, Laacher See Tephra and Vedde Ash in the Monts du Forez Mountains, in the Massif du Pilat, in the Jura Mountains, in the Northern Alps and on the Western Swiss Plateau. 1. Clermont-Ferrand basin (Raynal et al., 1994; Vernet and Raynal, 1995; Vernet et al., 1996; Miallier et al., 2004; Vernet, 2013; Boivin et al., 2017), 2. Gourd des Allières (Etlicher et al., 1987), 3. Gourgon, 4. Molhiac, 5. Digonnière, 6. Narse du Béage (Dendievel et al., 2015), 7. Annecy (Brauer and Casanova, 2001; Nomade, 2005), 8. Onoz (Magny and Ruffaldi, 1994; Walter-Simonnet et al., 2008), 9. Chalain (Martini and Duret, 1965; Jouannic et al., 2015), 10. Val (Jouannic et al., 2015), 11. Bellefontaine (Martini, 1970; Jouannic et al., 2015), 12. Lautrey (Bossuet et al., 1997; Vannière et al., 2004; Walter-Simonnet et al., 2008), 13. Saint-Point (Leroux, 2010), 14. Rances (Martini, 1970; Eicher, 1987) 15. Gerzensee (Eicher and Siegenthaler, 1976; Eicher, 1987; Lotter et al., 1992; Walter-Simonnet et al., 2008), 16. Dittligersee (Martini, 1970), 17. Burgäschi (Martini, 1970; van den Bogaard and Schminke, 1985), 18. Soppensee (Lotter et al., 1992; Blockley et al., 2007; Lane et al., 2011b), 19. Lucerne (Schnellman et al., 2006).

869

870

871

872

873

874

875

876

877

878

879

880

881

882

883

884

885

886

Table 1: Radiocarbon dates performed on peat for the stratigraphies of Molhiac, Gourgon and Digonnière, Massif Central (France).

887

888
Table 2: Non-normalized major oxides concentrations of volcanic glass shards of tephras found in the peat stratigraphies of Gourgon, Molhiac and Digonnière, Massif Central (France).

892

Table 3: Radiocarbon ages and age estimates of tephra layers found in the peat stratigraphies of Gourgon, Molhiac and Digonnière, Massif Central (France).

894

895
<figure><img src="image_2.png" /></figure>

45°40′N

4°00′E

4°20′E

N

Gourgon

<figure><img src="image_3.png" /></figure>

Montbrison

<figure><img src="image_4.png" /></figure>

MONTS
DU
FOREZ

Moilhiac

<figure><img src="image_5.png" /></figure>

45°30′N

Ambert

<figure><img src="image_6.png" /></figure>

MONTS
DU
LYONNAIS

Saint-Etienne

<figure><img src="image_7.png" /></figure>

MASSIF
DU
PILAT

<figure><img src="image_8.png" /></figure>

Digounière

<figure><img src="image_9.png" /></figure>

study site

<figure><img src="image_10.png" /></figure>

town

10 km

<figure><img src="image_11.png" /></figure>

Chaîne
des Puys

FRANCE
GOURGON

<figure><img src="image_12.png" /></figure>
DIGONNIERE

<figure><img src="image_13.png" /></figure>

<figure><img src="image_14.png" /></figure>
Molhiac

Magnetic
susceptibility
(10⁻⁶ SI)

<figure><img src="image_15.png" /></figure>

Magnetic
susceptibility

<figure><img src="image_16.png" /></figure>

Ti (cps)

<figure><img src="image_17.png" /></figure>

Zr (cps)

<figure><img src="image_18.png" /></figure>

K (cps)

<figure><img src="image_19.png" /></figure>

Scanner

<figure><img src="image_20.png" /></figure>

Int.

<figure><img src="image_21.png" /></figure>

Age
(cal. BP)

[6396-6278]

MF1

[5995-5753]

Magnetic
susceptibility

<figure><img src="image_22.png" /></figure>

Ti (cps)

<figure><img src="image_23.png" /></figure>

Zr (cps)

<figure><img src="image_24.png" /></figure>

K (cps)

<figure><img src="image_25.png" /></figure>

Scanner

<figure><img src="image_26.png" /></figure>

Int.

<figure><img src="image_27.png" /></figure>

Age
(cal. BP)

M2

M3

[11402-11203]

Peat

Granitic sand

Tephra

Radiocarbon date
Age (year cal. BP)

<figure><img src="image_28.png" /></figure>

<figure><img src="image_29.png" /></figure>

<figure><img src="image_30.png" /></figure>

<figure><img src="image_31.png" /></figure>

Age (year cal. BP)
<figure><img src="image_32.png" /></figure>

<figure><img src="image_33.png" /></figure>

<figure><img src="image_34.png" /></figure>

<figure><img src="image_35.png" /></figure>

<figure><img src="image_36.png" /></figure>

<figure><img src="image_37.png" /></figure>
<figure><img src="image_38.png" /></figure>

<figure><img src="image_39.png" /></figure>

<figure><img src="image_40.png" /></figure>

<figure><img src="image_41.png" /></figure>

<figure><img src="image_42.png" /></figure>

<figure><img src="image_43.png" /></figure>

X Kilian lavas

● Vasset lavas

Chopine lavas and pyroclastic flows

<figure><img src="image_44.png" /></figure>

CF5

<figure><img src="image_45.png" /></figure>

Marsat Formation

<figure><img src="image_46.png" /></figure>

Nugère tephra

<figure><img src="image_47.png" /></figure>

<figure><img src="image_48.png" /></figure>

Val 12-374.5/Sop-T4.74

<figure><img src="image_49.png" /></figure>

<figure><img src="image_50.png" /></figure>

<figure><img src="image_51.png" /></figure>
<figure><img src="image_52.png" /></figure>
<figure><img src="image_53.png" /></figure>

Clermont-Ferrand
(Vernet, 1992)

CHAÎNE DES PUYS

Clermont-Ferrand

Gourgon/Molhiac

<figure><img src="image_54.png" /></figure>

<figure><img src="image_55.png" /></figure>

Gourd des Allières
(Etlicher et al., 1987)

<figure><img src="image_56.png" /></figure>

<figure><img src="image_57.png" /></figure>

Lyon

Digonnière

<figure><img src="image_58.png" /></figure>

Saint-Etienne

<figure><img src="image_59.png" /></figure>

Le Béage
(Dendievel et al., 2015)

?

Valence

100 km
<figure><img src="image_60.png" /></figure>

Chaîne des Puys
Feuille1

<table><thead><tr><th>Site</th><th>Depth (cm)</th><th>Radiocarbon date (BP)</th><th>Calibrated age BP (2σ)</th><th>Laboratory reference</th><th>Material</th></tr></thead><tbody><tr><td>Molhiac</td><td>63</td><td>5,520 ± 35</td><td>6,396 – 6,278</td><td>Poz-57235</td><td>peat</td></tr><tr><td>Molhiac</td><td>70</td><td>5,150 ± 40</td><td>5,995 – 5,753</td><td>Lyon-9664(GrA)</td><td>peat</td></tr><tr><td>Molhiac</td><td>200</td><td>9,890 ± 45</td><td>11,404 – 11,203</td><td>Lyon-9665(GrA)</td><td>peat</td></tr><tr><td>Gourgon</td><td>170</td><td>5,860 ± 40</td><td>6,752 – 6,559</td><td>Lyon-9663(GrA)</td><td>peat</td></tr><tr><td>Gourgon</td><td>230</td><td>8,015 ± 45</td><td>9,015 – 8,717</td><td>Lyon-9662(GrA)</td><td>peat</td></tr><tr><td>Gourgon</td><td>252</td><td>9,110 ± 30</td><td>10,372 – 10,201</td><td>Beta 471197</td><td>peat</td></tr><tr><td>Gourgon</td><td>270</td><td>10,270 ± 50</td><td>12,453 – 11,817</td><td>Lyon-9661(GrA)</td><td>peat</td></tr><tr><td>Gourgon</td><td>277</td><td>11,410 ± 30</td><td>13,342 – 13,179</td><td>Beta 471198</td><td>peat</td></tr><tr><td>Gourgon</td><td>285</td><td>11,450 ± 50</td><td>13,449 – 13,184</td><td>Lyon-9660(GrA)</td><td>peat</td></tr><tr><td>Digonnière</td><td>153</td><td>5,240 ± 30</td><td>6,175 – 5,920</td><td>Beta 471195</td><td>peat</td></tr><tr><td>Digonnière</td><td>221</td><td>8,580 ± 30</td><td>9,597 – 9,487</td><td>Beta 471196</td><td>peat</td></tr></tbody></table>
Feuille1

<table><thead><tr><th>Site/Tephra</th><th>EPMA#</th><th>SiO2</th><th>TiO2</th><th>Al2O3</th><th>FeO<sub>tot</sub></th><th>MnO</th></tr></thead><tbody><tr><td rowspan="28">Gourgon / MF1</td><td>1</td><td>72.16</td><td>0.04</td><td>11.51</td><td>0.70</td><td>0.17</td></tr><tr><td>2</td><td>66.66</td><td>0.21</td><td>14.33</td><td>1.31</td><td>0.17</td></tr><tr><td>3</td><td>73.11</td><td>0.04</td><td>12.04</td><td>0.67</td><td>0.04</td></tr><tr><td>4</td><td>69.41</td><td>0.11</td><td>14.60</td><td>1.27</td><td>0.18</td></tr><tr><td>5</td><td>70.27</td><td>0.36</td><td>12.44</td><td>0.58</td><td>0.10</td></tr><tr><td>6</td><td>71.11</td><td>0.24</td><td>14.96</td><td>1.24</td><td>0.10</td></tr><tr><td>7</td><td>72.97</td><td>0.00</td><td>12.30</td><td>0.72</td><td>0.09</td></tr><tr><td>8</td><td>70.88</td><td>0.04</td><td>11.33</td><td>0.69</td><td>0.09</td></tr><tr><td>9</td><td>72.98</td><td>0.15</td><td>11.83</td><td>0.66</td><td>0.09</td></tr><tr><td>10</td><td>68.40</td><td>0.17</td><td>14.92</td><td>1.25</td><td>0.20</td></tr><tr><td>11</td><td>66.10</td><td>0.27</td><td>14.36</td><td>1.21</td><td>0.07</td></tr><tr><td>12</td><td>69.38</td><td>0.29</td><td>14.43</td><td>1.40</td><td>-</td></tr><tr><td>13</td><td>65.74</td><td>0.26</td><td>13.38</td><td>1.52</td><td>0.23</td></tr><tr><td>14</td><td>71.58</td><td>0.07</td><td>11.94</td><td>0.55</td><td>0.05</td></tr><tr><td>15</td><td>68.77</td><td>0.26</td><td>14.53</td><td>0.90</td><td>0.20</td></tr><tr><td>16</td><td>75.02</td><td>0.43</td><td>11.05</td><td>1.04</td><td>-</td></tr><tr><td>17</td><td>68.75</td><td>0.30</td><td>13.59</td><td>1.42</td><td>0.10</td></tr><tr><td>18</td><td>70.40</td><td>0.30</td><td>14.35</td><td>1.28</td><td>-</td></tr><tr><td>19</td><td>70.16</td><td>0.22</td><td>14.20</td><td>1.11</td><td>-</td></tr><tr><td>20</td><td>69.93</td><td>0.27</td><td>14.73</td><td>1.13</td><td>-</td></tr><tr><td>21</td><td>72.88</td><td>0.10</td><td>12.05</td><td>0.61</td><td>0.03</td></tr><tr><td>22</td><td>69.08</td><td>0.24</td><td>14.65</td><td>1.40</td><td>0.24</td></tr><tr><td>23</td><td>71.48</td><td>0.13</td><td>12.24</td><td>0.74</td><td>-</td></tr><tr><td>24</td><td>69.31</td><td>0.27</td><td>14.37</td><td>1.29</td><td>0.21</td></tr><tr><td>25</td><td>73.64</td><td>0.04</td><td>12.16</td><td>0.77</td><td>0.03</td></tr><tr><td>26</td><td>67.99</td><td>0.22</td><td>14.64</td><td>1.18</td><td>0.30</td></tr><tr><td>27</td><td>68.42</td><td>0.17</td><td>13.92</td><td>0.86</td><td>0.30</td></tr><tr><td>28</td><td>67.21</td><td>0.29</td><td>15.09</td><td>1.64</td><td>0.04</td></tr><tr><td>Mean</td><td></td><td>70.14</td><td>0.20</td><td>13.43</td><td>1.04</td><td>0.14</td></tr><tr><td>Std dev</td><td></td><td>2.37</td><td>0.11</td><td>1.33</td><td>0.33</td><td>0.09</td></tr><tr><td rowspan="13">Gourgon / G2</td><td>1</td><td>67.31</td><td>0.00</td><td>18.88</td><td>0.41</td><td>0.00</td></tr><tr><td>2</td><td>64.62</td><td>0.08</td><td>19.10</td><td>0.26</td><td>0.00</td></tr><tr><td>3</td><td>67.03</td><td>0.29</td><td>13.94</td><td>2.02</td><td>0.00</td></tr><tr><td>4</td><td>65.66</td><td>0.00</td><td>20.68</td><td>0.37</td><td>0.00</td></tr><tr><td>5</td><td>62.00</td><td>0.04</td><td>21.16</td><td>0.34</td><td>0.17</td></tr><tr><td>6</td><td>64.02</td><td>0.08</td><td>17.25</td><td>1.74</td><td>0.08</td></tr><tr><td>7</td><td>63.11</td><td>0.08</td><td>14.16</td><td>1.25</td><td>0.09</td></tr><tr><td>8</td><td>64.23</td><td>0.18</td><td>14.76</td><td>0.89</td><td>0.11</td></tr><tr><td>9</td><td>62.93</td><td>0.07</td><td>14.90</td><td>0.42</td><td>0.10</td></tr><tr><td>10</td><td>64.30</td><td>0.13</td><td>17.29</td><td>1.67</td><td>0.11</td></tr><tr><td>11</td><td>63.90</td><td>0.09</td><td>16.12</td><td>0.95</td><td>0.10</td></tr><tr><td>12</td><td>63.98</td><td>0.16</td><td>16.42</td><td>1.69</td><td>0.09</td></tr><tr><td>13</td><td>63.11</td><td>0.16</td><td>16.40</td><td>0.46</td><td>0.10</td></tr></tbody></table>
Feuille1

<table><tbody><tr><td></td><td>14</td><td>67.12</td><td>0.46</td><td>15.38</td><td>1.96</td><td>0.21</td></tr><tr><td></td><td>15</td><td>66.07</td><td>0.13</td><td>18.31</td><td>0.70</td><td>0.02</td></tr><tr><td></td><td>16</td><td>66.53</td><td>0.29</td><td>16.49</td><td>1.35</td><td>0.21</td></tr><tr><td></td><td>17</td><td>66.66</td><td>0.18</td><td>18.23</td><td>0.87</td><td>0.03</td></tr><tr><td></td><td>18</td><td>65.44</td><td>0.10</td><td>19.01</td><td>0.62</td><td>0.09</td></tr><tr><td></td><td>19</td><td>65.50</td><td>0.22</td><td>18.61</td><td>1.25</td><td>0.14</td></tr><tr><td></td><td>20</td><td>64.86</td><td>0.04</td><td>20.25</td><td>0.48</td><td>0.00</td></tr><tr><td>Mean</td><td></td><td>64.92</td><td>0.14</td><td>17.37</td><td>0.99</td><td>0.08</td></tr><tr><td>Std dev</td><td></td><td>1.55</td><td>0.11</td><td>2.15</td><td>0.59</td><td>0.07</td></tr><tr><td>Gourgon / G3</td><td>1</td><td>67.13</td><td>0.40</td><td>18.79</td><td>2.37</td><td>0.00</td></tr><tr><td></td><td>2</td><td>63.81</td><td>0.03</td><td>19.11</td><td>1.51</td><td>0.00</td></tr><tr><td></td><td>3</td><td>67.01</td><td>0.43</td><td>16.79</td><td>2.30</td><td>0.00</td></tr><tr><td></td><td>4</td><td>65.01</td><td>0.45</td><td>17.64</td><td>2.27</td><td>0.00</td></tr><tr><td></td><td>5</td><td>66.72</td><td>0.07</td><td>16.91</td><td>2.15</td><td>0.00</td></tr><tr><td></td><td>6</td><td>66.80</td><td>0.44</td><td>18.10</td><td>1.63</td><td>0.00</td></tr><tr><td></td><td>7</td><td>64.61</td><td>0.35</td><td>17.07</td><td>2.30</td><td>0.00</td></tr><tr><td></td><td>8</td><td>66.89</td><td>0.29</td><td>17.91</td><td>2.23</td><td>0.00</td></tr><tr><td></td><td>9</td><td>65.94</td><td>0.37</td><td>17.84</td><td>1.99</td><td>0.00</td></tr><tr><td></td><td>10</td><td>63.90</td><td>0.38</td><td>18.04</td><td>1.96</td><td>0.00</td></tr><tr><td></td><td>11</td><td>63.99</td><td>0.36</td><td>17.57</td><td>2.06</td><td>0.00</td></tr><tr><td></td><td>12</td><td>65.38</td><td>0.33</td><td>17.71</td><td>2.12</td><td>0.00</td></tr><tr><td></td><td>13</td><td>65.70</td><td>0.34</td><td>17.71</td><td>2.07</td><td>0.00</td></tr><tr><td></td><td>14</td><td>67.01</td><td>0.38</td><td>17.59</td><td>2.06</td><td>0.00</td></tr><tr><td></td><td>15</td><td>66.82</td><td>0.33</td><td>17.64</td><td>2.10</td><td>0.00</td></tr><tr><td>Mean</td><td></td><td>65.78</td><td>0.33</td><td>17.76</td><td>2.07</td><td>0.00</td></tr><tr><td>Std dev</td><td></td><td>1.25</td><td>0.12</td><td>0.62</td><td>0.24</td><td>0.00</td></tr><tr><td>Gourgon / G4</td><td>1</td><td>47.43</td><td>2.31</td><td>15.77</td><td>11.67</td><td>0.21</td></tr><tr><td></td><td>2</td><td>50.39</td><td>2.35</td><td>17.36</td><td>10.74</td><td>0.20</td></tr><tr><td></td><td>3</td><td>48.80</td><td>2.34</td><td>15.94</td><td>10.82</td><td>0.21</td></tr><tr><td></td><td>4</td><td>49.68</td><td>2.33</td><td>17.11</td><td>10.83</td><td>0.21</td></tr><tr><td></td><td>5</td><td>49.17</td><td>2.33</td><td>17.19</td><td>11.41</td><td>0.21</td></tr><tr><td></td><td>6</td><td>47.47</td><td>2.33</td><td>16.42</td><td>10.91</td><td>0.21</td></tr><tr><td></td><td>7</td><td>48.06</td><td>2.33</td><td>16.01</td><td>11.06</td><td>0.21</td></tr><tr><td></td><td>8</td><td>48.00</td><td>2.34</td><td>16.01</td><td>11.14</td><td>0.20</td></tr><tr><td></td><td>9</td><td>49.35</td><td>2.35</td><td>16.28</td><td>11.27</td><td>0.21</td></tr><tr><td></td><td>10</td><td>49.37</td><td>2.34</td><td>17.27</td><td>10.77</td><td>0.20</td></tr><tr><td>Mean</td><td></td><td>48.77</td><td>2.34</td><td>16.54</td><td>11.06</td><td>0.21</td></tr><tr><td>Std dev</td><td></td><td>0.99</td><td>0.01</td><td>0.63</td><td>0.31</td><td>0.00</td></tr><tr><td>Gourgon / G5</td><td>1</td><td>66.00</td><td>0.80</td><td>17.60</td><td>3.62</td><td>0.21</td></tr><tr><td></td><td>2</td><td>65.40</td><td>0.50</td><td>17.50</td><td>3.30</td><td>0.23</td></tr><tr><td></td><td>3</td><td>64.50</td><td>0.55</td><td>17.70</td><td>3.40</td><td>0.13</td></tr><tr><td></td><td>4</td><td>64.50</td><td>0.40</td><td>17.50</td><td>4.00</td><td>0.13</td></tr><tr><td></td><td>5</td><td>65.69</td><td>0.48</td><td>17.66</td><td>3.80</td><td>0.15</td></tr></tbody></table>
Feuille1

<table><tbody><tr><td></td><td>6</td><td>64.63</td><td>0.60</td><td>17.68</td><td>3.73</td><td>0.22</td></tr><tr><td></td><td>7</td><td>65.85</td><td>0.62</td><td>17.70</td><td>3.34</td><td>0.13</td></tr><tr><td></td><td>8</td><td>65.59</td><td>0.71</td><td>17.56</td><td>3.65</td><td>0.23</td></tr><tr><td></td><td>9</td><td>65.77</td><td>0.72</td><td>17.57</td><td>3.97</td><td>0.16</td></tr><tr><td></td><td>10</td><td>65.29</td><td>0.76</td><td>17.66</td><td>3.31</td><td>0.15</td></tr><tr><td></td><td>11</td><td>64.94</td><td>0.80</td><td>17.63</td><td>3.30</td><td>0.14</td></tr><tr><td></td><td>12</td><td>64.99</td><td>0.56</td><td>17.64</td><td>3.70</td><td>0.15</td></tr><tr><td></td><td>Mean</td><td>65.26</td><td>0.63</td><td>17.62</td><td>3.59</td><td>0.17</td></tr><tr><td></td><td>Std dev</td><td>0.54</td><td>0.13</td><td>0.07</td><td>0.26</td><td>0.04</td></tr><tr><td rowspan="14">Gourgon / G6</td><td>1</td><td>58.07</td><td>1.71</td><td>17.11</td><td>5.20</td><td>0.10</td></tr><tr><td>2</td><td>57.24</td><td>2.01</td><td>15.32</td><td>7.65</td><td>0.39</td></tr><tr><td>3</td><td>55.98</td><td>2.16</td><td>15.09</td><td>7.48</td><td>0.33</td></tr><tr><td>4</td><td>56.07</td><td>1.98</td><td>16.49</td><td>7.55</td><td>0.21</td></tr><tr><td>5</td><td>56.98</td><td>1.99</td><td>15.76</td><td>7.34</td><td>0.46</td></tr><tr><td>6</td><td>54.49</td><td>2.10</td><td>16.20</td><td>7.13</td><td>0.05</td></tr><tr><td>7</td><td>55.80</td><td>1.91</td><td>14.72</td><td>6.49</td><td>0.33</td></tr><tr><td>8</td><td>53.00</td><td>2.11</td><td>16.25</td><td>6.79</td><td>0.16</td></tr><tr><td>9</td><td>55.55</td><td>2.11</td><td>15.66</td><td>7.30</td><td>-</td></tr><tr><td>10</td><td>56.63</td><td>2.15</td><td>16.22</td><td>7.50</td><td>0.26</td></tr><tr><td>11</td><td>57.41</td><td>1.52</td><td>18.48</td><td>6.12</td><td>0.11</td></tr><tr><td>12</td><td>50.52</td><td>1.95</td><td>15.33</td><td>7.34</td><td>0.18</td></tr><tr><td>13</td><td>57.52</td><td>0.85</td><td>22.12</td><td>2.40</td><td>0.09</td></tr><tr><td>14</td><td>53.25</td><td>1.43</td><td>16.96</td><td>6.03</td><td>0.11</td></tr><tr><td>Mean</td><td></td><td>55.61</td><td>1.86</td><td>16.55</td><td>6.59</td><td>0.21</td></tr><tr><td>Std dev</td><td></td><td>2.12</td><td>0.37</td><td>1.87</td><td>1.40</td><td>0.14</td></tr><tr><td rowspan="14">Molhiac / M1</td><td>1</td><td>78.21</td><td>0.33</td><td>8.14</td><td>1.08</td><td>0.00</td></tr><tr><td>2</td><td>70.20</td><td>0.08</td><td>12.63</td><td>1.03</td><td>0.10</td></tr><tr><td>3</td><td>68.85</td><td>0.22</td><td>13.64</td><td>1.31</td><td>0.15</td></tr><tr><td>4</td><td>74.01</td><td>0.03</td><td>13.26</td><td>0.38</td><td>0.00</td></tr><tr><td>5</td><td>71.51</td><td>0.22</td><td>16.22</td><td>1.25</td><td>0.02</td></tr><tr><td>6</td><td>76.08</td><td>0.26</td><td>9.77</td><td>1.16</td><td>0.08</td></tr><tr><td>7</td><td>71.85</td><td>0.08</td><td>11.00</td><td>0.58</td><td>0.09</td></tr><tr><td>8</td><td>73.06</td><td>0.11</td><td>14.84</td><td>1.07</td><td>0.01</td></tr><tr><td>9</td><td>71.78</td><td>0.03</td><td>13.33</td><td>0.40</td><td>0.08</td></tr><tr><td>10</td><td>76.08</td><td>0.15</td><td>13.67</td><td>0.48</td><td>0.05</td></tr><tr><td>11</td><td>71.86</td><td>0.05</td><td>14.67</td><td>0.84</td><td>0.08</td></tr><tr><td>12</td><td>74.77</td><td>0.07</td><td>12.72</td><td>0.77</td><td>0.08</td></tr><tr><td>Mean</td><td></td><td>73.19</td><td>0.14</td><td>12.82</td><td>0.86</td><td>0.06</td></tr><tr><td>Std dev</td><td></td><td>2.72</td><td>0.10</td><td>2.25</td><td>0.34</td><td>0.05</td></tr><tr><td rowspan="4">Molhiac / M2</td><td>1</td><td>63.50</td><td>0.06</td><td>14.70</td><td>0.48</td><td>0.15</td></tr><tr><td>2</td><td>63.62</td><td>0.28</td><td>16.79</td><td>0.34</td><td>0.11</td></tr><tr><td>3</td><td>65.24</td><td>0.18</td><td>15.76</td><td>1.30</td><td>0.00</td></tr><tr><td>4</td><td>62.34</td><td>0.05</td><td>17.58</td><td>1.18</td><td>0.12</td></tr></tbody></table>
Feuille1

<table><tr><td>5</td><td>66.27</td><td>0.09</td><td>14.02</td><td>1.07</td><td>0.00</td></tr><tr><td>6</td><td>66.80</td><td>0.11</td><td>18.72</td><td>1.91</td><td>0.14</td></tr><tr><td>7</td><td>64.41</td><td>0.14</td><td>14.73</td><td>1.01</td><td>0.17</td></tr><tr><td>8</td><td>65.42</td><td>0.15</td><td>17.43</td><td>1.23</td><td>0.00</td></tr><tr><td>9</td><td>65.16</td><td>0.01</td><td>16.21</td><td>0.87</td><td>0.00</td></tr><tr><td>10</td><td>66.15</td><td>0.04</td><td>18.32</td><td>0.38</td><td>0.09</td></tr><tr><td>11</td><td>65.61</td><td>0.28</td><td>14.60</td><td>0.33</td><td>0.00</td></tr><tr><td>12</td><td>65.71</td><td>0.28</td><td>17.85</td><td>1.41</td><td>0.12</td></tr><tr><td>Mean</td><td>65.02</td><td>0.14</td><td>16.39</td><td>0.96</td><td>0.08</td></tr><tr><td>Std dev</td><td>1.31</td><td>0.10</td><td>1.62</td><td>0.50</td><td>0.07</td></tr></table>

<table><tr><td>Molhiac / M3</td><td>1</td><td>66.48</td><td>0.37</td><td>17.45</td><td>1.82</td><td>0.00</td></tr><tr><td></td><td>2</td><td>66.81</td><td>0.33</td><td>17.95</td><td>1.77</td><td>0.00</td></tr><tr><td></td><td>3</td><td>66.72</td><td>0.05</td><td>18.56</td><td>2.27</td><td>0.00</td></tr><tr><td></td><td>4</td><td>65.85</td><td>0.20</td><td>17.98</td><td>2.30</td><td>0.00</td></tr><tr><td></td><td>5</td><td>66.84</td><td>0.37</td><td>18.03</td><td>2.32</td><td>0.00</td></tr><tr><td></td><td>6</td><td>66.71</td><td>0.10</td><td>17.16</td><td>2.10</td><td>0.00</td></tr><tr><td></td><td>7</td><td>66.12</td><td>0.06</td><td>18.43</td><td>1.68</td><td>0.00</td></tr><tr><td></td><td>8</td><td>66.55</td><td>0.17</td><td>17.94</td><td>2.02</td><td>0.00</td></tr><tr><td></td><td>9</td><td>66.61</td><td>0.17</td><td>18.69</td><td>1.59</td><td>0.00</td></tr><tr><td></td><td>10</td><td>65.61</td><td>0.28</td><td>18.95</td><td>2.35</td><td>0.00</td></tr><tr><td>Mean</td><td></td><td>66.43</td><td>0.21</td><td>18.11</td><td>2.02</td><td>0.00</td></tr><tr><td>Std dev</td><td></td><td>0.43</td><td>0.12</td><td>0.55</td><td>0.29</td><td>0.00</td></tr></table>

<table><tr><td>Digonnière / D1</td><td>1</td><td>68.62</td><td>0.25</td><td>14.49</td><td>0.96</td><td>0.19</td></tr><tr><td></td><td>2</td><td>68.77</td><td>0.21</td><td>14.65</td><td>1.40</td><td>0.13</td></tr><tr><td></td><td>3</td><td>68.81</td><td>0.30</td><td>14.44</td><td>1.05</td><td>0.09</td></tr><tr><td></td><td>4</td><td>68.16</td><td>0.20</td><td>14.42</td><td>0.93</td><td>0.17</td></tr><tr><td></td><td>5</td><td>68.75</td><td>0.24</td><td>14.02</td><td>1.07</td><td>0.14</td></tr><tr><td></td><td>6</td><td>69.53</td><td>0.27</td><td>14.70</td><td>1.30</td><td>0.15</td></tr><tr><td></td><td>7</td><td>69.51</td><td>0.26</td><td>14.64</td><td>1.21</td><td>0.05</td></tr><tr><td></td><td>8</td><td>68.36</td><td>0.26</td><td>14.55</td><td>1.19</td><td>0.08</td></tr><tr><td>Mean</td><td></td><td>68.81</td><td>0.25</td><td>14.49</td><td>1.14</td><td>0.13</td></tr><tr><td>Std dev</td><td></td><td>0.49</td><td>0.03</td><td>0.22</td><td>0.16</td><td>0.05</td></tr></table>

<table><tr><td>Digonnière / D2</td><td>1</td><td>66.08</td><td>0.26</td><td>16.79</td><td>1.66</td><td>0.25</td></tr><tr><td></td><td>2</td><td>66.23</td><td>0.21</td><td>16.95</td><td>2.10</td><td>0.19</td></tr><tr><td></td><td>3</td><td>66.27</td><td>0.31</td><td>16.74</td><td>1.75</td><td>0.15</td></tr><tr><td></td><td>4</td><td>65.62</td><td>0.20</td><td>16.73</td><td>1.64</td><td>0.23</td></tr><tr><td></td><td>5</td><td>66.75</td><td>0.29</td><td>16.75</td><td>2.08</td><td>0.13</td></tr><tr><td></td><td>6</td><td>66.21</td><td>0.25</td><td>16.33</td><td>1.77</td><td>0.20</td></tr><tr><td></td><td>7</td><td>67.00</td><td>0.24</td><td>16.67</td><td>1.09</td><td>0.21</td></tr><tr><td></td><td>8</td><td>66.99</td><td>0.27</td><td>17.00</td><td>2.00</td><td>0.22</td></tr><tr><td></td><td>9</td><td>65.82</td><td>0.26</td><td>16.86</td><td>1.89</td><td>0.15</td></tr><tr><td></td><td>10</td><td>66.97</td><td>0.20</td><td>16.65</td><td>2.43</td><td>0.24</td></tr><tr><td>Mean</td><td></td><td>66.39</td><td>0.25</td><td>16.75</td><td>1.84</td><td>0.20</td></tr></table>
Feuille1

<table><thead><tr><th>Std dev</th><th></th><th>0.50</th><th>0.04</th><th>0.19</th><th>0.36</th><th>0.04</th></tr></thead><tbody><tr><td rowspan="10">A99*</td><td>1</td><td>50.63</td><td>4.16</td><td>12.55</td><td>13.11</td><td>0.10</td></tr><tr><td>2</td><td>51.23</td><td>4.22</td><td>12.89</td><td>13.07</td><td>0.22</td></tr><tr><td>3</td><td>51.26</td><td>4.12</td><td>12.62</td><td>12.57</td><td>0.20</td></tr><tr><td>4</td><td>51.62</td><td>4.09</td><td>12.71</td><td>12.98</td><td>0.18</td></tr><tr><td>5</td><td>51.03</td><td>4.16</td><td>12.66</td><td>12.99</td><td>0.09</td></tr><tr><td>6</td><td>50.95</td><td>4.22</td><td>12.73</td><td>13.84</td><td>0.22</td></tr><tr><td>7</td><td>50.97</td><td>4.13</td><td>12.55</td><td>13.01</td><td>0.20</td></tr><tr><td>8</td><td>50.67</td><td>4.11</td><td>12.64</td><td>13.01</td><td>0.20</td></tr><tr><td>9</td><td>50.49</td><td>4.09</td><td>12.58</td><td>13.26</td><td>0.23</td></tr><tr><td>10</td><td>50.74</td><td>4.08</td><td>12.67</td><td>12.93</td><td>0.22</td></tr><tr><td>Mean</td><td></td><td>50.96</td><td>4.14</td><td>12.66</td><td>13.08</td><td>0.19</td></tr><tr><td>Std dev</td><td></td><td>0.34</td><td>0.05</td><td>0.10</td><td>0.32</td><td>0.05</td></tr></tbody></table>

<footnote>* Standard (natural glasses) used for calibration (Óladóttir et al., 2011)</footnote>
Feuille1

<table><thead><tr><th>MgO</th><th>CaO</th><th>Na2O</th><th>K2O</th><th>Sum</th></tr></thead><tbody><tr><td>0.01</td><td>0.40</td><td>1.65</td><td>4.59</td><td>91.23</td></tr><tr><td>0.13</td><td>0.61</td><td>3.87</td><td>5.31</td><td>92.60</td></tr><tr><td>0.00</td><td>0.30</td><td>3.63</td><td>4.63</td><td>94.48</td></tr><tr><td>0.10</td><td>0.51</td><td>4.17</td><td>5.54</td><td>95.88</td></tr><tr><td>0.15</td><td>0.67</td><td>3.06</td><td>5.23</td><td>92.86</td></tr><tr><td>0.09</td><td>0.84</td><td>4.23</td><td>6.34</td><td>99.17</td></tr><tr><td>0.10</td><td>0.37</td><td>2.26</td><td>4.74</td><td>93.54</td></tr><tr><td>0.03</td><td>0.42</td><td>2.83</td><td>4.63</td><td>90.97</td></tr><tr><td>0.07</td><td>0.41</td><td>3.49</td><td>4.91</td><td>94.58</td></tr><tr><td>0.09</td><td>0.83</td><td>3.87</td><td>5.36</td><td>95.11</td></tr><tr><td>0.04</td><td>0.55</td><td>3.92</td><td>5.06</td><td>91.58</td></tr><tr><td>0.09</td><td>0.94</td><td>4.00</td><td>6.01</td><td>96.53</td></tr><tr><td>0.13</td><td>0.52</td><td>5.14</td><td>5.27</td><td>92.18</td></tr><tr><td>0.00</td><td>0.39</td><td>3.15</td><td>4.68</td><td>92.41</td></tr><tr><td>0.12</td><td>0.55</td><td>4.83</td><td>5.40</td><td>95.63</td></tr><tr><td>0.07</td><td>0.17</td><td>2.28</td><td>6.93</td><td>97.00</td></tr><tr><td>0.15</td><td>0.69</td><td>3.55</td><td>6.09</td><td>94.65</td></tr><tr><td>0.14</td><td>0.52</td><td>3.64</td><td>6.39</td><td>97.03</td></tr><tr><td>0.21</td><td>0.91</td><td>4.34</td><td>6.00</td><td>97.15</td></tr><tr><td>0.10</td><td>0.92</td><td>3.97</td><td>5.71</td><td>96.91</td></tr><tr><td>0.05</td><td>0.36</td><td>3.32</td><td>5.07</td><td>94.54</td></tr><tr><td>0.13</td><td>0.69</td><td>4.94</td><td>5.47</td><td>96.84</td></tr><tr><td>0.08</td><td>0.35</td><td>3.43</td><td>4.22</td><td>92.70</td></tr><tr><td>0.09</td><td>0.63</td><td>5.21</td><td>5.46</td><td>96.85</td></tr><tr><td>0.07</td><td>0.31</td><td>2.60</td><td>5.01</td><td>94.66</td></tr><tr><td>0.07</td><td>0.61</td><td>5.22</td><td>5.50</td><td>95.76</td></tr><tr><td>0.07</td><td>0.47</td><td>4.70</td><td>5.06</td><td>93.97</td></tr><tr><td>0.12</td><td>0.64</td><td>5.13</td><td>5.30</td><td>95.48</td></tr><tr><td>0.09</td><td>0.56</td><td>3.80</td><td>5.35</td><td></td></tr><tr><td>0.05</td><td>0.20</td><td>0.96</td><td>0.62</td><td></td></tr><tr><td>0.04</td><td>0.23</td><td>7.11</td><td>6.49</td><td>100.47</td></tr><tr><td>0.00</td><td>1.06</td><td>4.66</td><td>7.60</td><td>97.39</td></tr><tr><td>0.35</td><td>1.24</td><td>4.17</td><td>5.90</td><td>95.12</td></tr><tr><td>0.01</td><td>1.62</td><td>6.86</td><td>5.48</td><td>100.69</td></tr><tr><td>0.01</td><td>2.91</td><td>6.42</td><td>4.09</td><td>97.21</td></tr><tr><td>0.09</td><td>2.32</td><td>5.51</td><td>4.27</td><td>95.35</td></tr><tr><td>0.15</td><td>2.87</td><td>4.23</td><td>4.47</td><td>90.41</td></tr><tr><td>0.32</td><td>2.69</td><td>5.29</td><td>4.79</td><td>93.25</td></tr><tr><td>0.09</td><td>2.36</td><td>6.69</td><td>4.40</td><td>91.96</td></tr><tr><td>0.25</td><td>2.69</td><td>5.79</td><td>4.36</td><td>96.34</td></tr><tr><td>0.13</td><td>2.69</td><td>4.99</td><td>4.30</td><td>93.27</td></tr><tr><td>0.15</td><td>2.83</td><td>6.60</td><td>4.48</td><td>96.38</td></tr><tr><td>0.12</td><td>2.60</td><td>5.55</td><td>4.37</td><td>92.87</td></tr></tbody></table>
Feuille1

<table><tr><td>0.22</td><td>0.70</td><td>5.37</td><td>5.82</td><td>97.20</td></tr><tr><td>0.06</td><td>0.84</td><td>6.58</td><td>6.28</td><td>99.00</td></tr><tr><td>0.15</td><td>0.70</td><td>5.77</td><td>6.03</td><td>97.50</td></tr><tr><td>0.05</td><td>1.01</td><td>6.85</td><td>5.50</td><td>99.40</td></tr><tr><td>0.02</td><td>0.99</td><td>7.08</td><td>5.50</td><td>98.90</td></tr><tr><td>0.12</td><td>1.92</td><td>6.72</td><td>4.34</td><td>98.80</td></tr><tr><td>0.02</td><td>2.23</td><td>8.10</td><td>3.37</td><td>99.40</td></tr><tr><td>0.12</td><td>1.83</td><td>6.02</td><td>5.09</td><td></td></tr><tr><td>0.10</td><td>0.89</td><td>1.05</td><td>1.04</td><td></td></tr><tr><td>0.60</td><td>0.06</td><td>6.39</td><td>5.50</td><td>101.25</td></tr><tr><td>0.55</td><td>0.07</td><td>6.29</td><td>5.69</td><td>97.04</td></tr><tr><td>0.40</td><td>1.29</td><td>5.91</td><td>4.99</td><td>99.11</td></tr><tr><td>0.56</td><td>1.53</td><td>5.57</td><td>4.31</td><td>97.34</td></tr><tr><td>0.44</td><td>0.71</td><td>5.76</td><td>4.32</td><td>97.08</td></tr><tr><td>0.54</td><td>0.62</td><td>5.84</td><td>5.35</td><td>99.32</td></tr><tr><td>0.52</td><td>0.95</td><td>6.32</td><td>5.33</td><td>97.45</td></tr><tr><td>0.49</td><td>0.75</td><td>5.68</td><td>4.48</td><td>98.70</td></tr><tr><td>0.46</td><td>0.88</td><td>6.15</td><td>5.11</td><td>98.74</td></tr><tr><td>0.54</td><td>0.69</td><td>5.91</td><td>5.32</td><td>96.74</td></tr><tr><td>0.49</td><td>0.74</td><td>6.26</td><td>4.74</td><td>96.20</td></tr><tr><td>0.48</td><td>0.73</td><td>5.92</td><td>4.92</td><td>97.58</td></tr><tr><td>0.50</td><td>0.71</td><td>6.28</td><td>5.09</td><td>98.40</td></tr><tr><td>0.53</td><td>0.69</td><td>6.20</td><td>5.16</td><td>99.62</td></tr><tr><td>0.51</td><td>0.73</td><td>5.79</td><td>4.92</td><td>98.84</td></tr><tr><td>0.51</td><td>0.74</td><td>6.02</td><td>5.02</td><td></td></tr><tr><td>0.05</td><td>0.37</td><td>0.26</td><td>0.41</td><td></td></tr><tr><td>4.31</td><td>8.90</td><td>4.98</td><td>3.42</td><td>99.00</td></tr><tr><td>3.48</td><td>8.14</td><td>4.18</td><td>2.13</td><td>98.97</td></tr><tr><td>3.75</td><td>8.71</td><td>4.28</td><td>3.12</td><td>97.97</td></tr><tr><td>3.89</td><td>8.77</td><td>4.77</td><td>2.58</td><td>100.16</td></tr><tr><td>3.99</td><td>8.19</td><td>4.79</td><td>2.62</td><td>99.90</td></tr><tr><td>3.98</td><td>8.62</td><td>4.70</td><td>2.22</td><td>96.86</td></tr><tr><td>3.81</td><td>8.48</td><td>4.91</td><td>3.29</td><td>98.17</td></tr><tr><td>3.65</td><td>8.40</td><td>4.63</td><td>3.36</td><td>97.73</td></tr><tr><td>3.69</td><td>8.41</td><td>4.85</td><td>2.82</td><td>99.23</td></tr><tr><td>3.59</td><td>8.22</td><td>4.56</td><td>3.39</td><td>99.71</td></tr><tr><td>3.81</td><td>8.48</td><td>4.67</td><td>2.90</td><td></td></tr><tr><td>0.24</td><td>0.26</td><td>0.26</td><td>0.49</td><td></td></tr><tr><td>0.50</td><td>1.60</td><td>5.60</td><td>4.80</td><td>100.73</td></tr><tr><td>0.64</td><td>1.75</td><td>5.70</td><td>4.50</td><td>99.52</td></tr><tr><td>0.21</td><td>1.10</td><td>5.10</td><td>4.50</td><td>97.19</td></tr><tr><td>0.36</td><td>1.30</td><td>5.10</td><td>4.40</td><td>97.69</td></tr><tr><td>0.41</td><td>1.17</td><td>5.45</td><td>4.59</td><td>99.40</td></tr></table>
Feuille1

<table><tr><td>0.63</td><td>1.68</td><td>5.24</td><td>4.56</td><td>98.97</td></tr><tr><td>0.36</td><td>1.48</td><td>5.21</td><td>4.67</td><td>99.36</td></tr><tr><td>0.38</td><td>1.12</td><td>5.32</td><td>4.49</td><td>99.04</td></tr><tr><td>0.48</td><td>1.60</td><td>5.34</td><td>4.77</td><td>100.38</td></tr><tr><td>0.47</td><td>1.12</td><td>5.22</td><td>4.41</td><td>98.39</td></tr><tr><td>0.29</td><td>1.10</td><td>5.52</td><td>4.56</td><td>98.27</td></tr><tr><td>0.22</td><td>1.35</td><td>5.47</td><td>4.65</td><td>98.73</td></tr><tr><td>0.41</td><td>1.36</td><td>5.36</td><td>4.58</td><td></td></tr><tr><td>0.14</td><td>0.25</td><td>0.19</td><td>0.13</td><td></td></tr><tr><td>1.37</td><td>3.68</td><td>6.38</td><td>4.63</td><td>99.00</td></tr><tr><td>1.49</td><td>3.79</td><td>4.57</td><td>4.64</td><td>97.98</td></tr><tr><td>2.01</td><td>4.63</td><td>5.53</td><td>4.31</td><td>98.35</td></tr><tr><td>2.43</td><td>4.68</td><td>5.25</td><td>4.81</td><td>100.35</td></tr><tr><td>2.58</td><td>4.82</td><td>4.80</td><td>4.19</td><td>99.71</td></tr><tr><td>2.09</td><td>4.83</td><td>5.33</td><td>4.14</td><td>97.15</td></tr><tr><td>2.50</td><td>5.06</td><td>5.20</td><td>4.21</td><td>97.18</td></tr><tr><td>2.23</td><td>5.08</td><td>5.64</td><td>4.17</td><td>96.32</td></tr><tr><td>2.47</td><td>5.17</td><td>4.98</td><td>3.94</td><td>98.00</td></tr><tr><td>2.42</td><td>5.18</td><td>4.90</td><td>4.00</td><td>100.09</td></tr><tr><td>1.68</td><td>5.86</td><td>4.96</td><td>3.21</td><td>99.91</td></tr><tr><td>1.87</td><td>7.32</td><td>5.76</td><td>4.74</td><td>98.07</td></tr><tr><td>0.76</td><td>7.78</td><td>5.43</td><td>1.55</td><td>98.75</td></tr><tr><td>3.11</td><td>8.28</td><td>4.67</td><td>2.51</td><td>96.94</td></tr><tr><td>2.07</td><td>5.44</td><td>5.24</td><td>3.93</td><td></td></tr><tr><td>0.60</td><td>1.40</td><td>0.49</td><td>0.92</td><td></td></tr><tr><td>0.26</td><td>0.27</td><td>2.61</td><td>4.15</td><td>95.05</td></tr><tr><td>0.05</td><td>0.57</td><td>3.81</td><td>5.54</td><td>94.01</td></tr><tr><td>0.08</td><td>0.41</td><td>4.50</td><td>5.26</td><td>94.42</td></tr><tr><td>0.26</td><td>0.47</td><td>3.22</td><td>4.31</td><td>95.94</td></tr><tr><td>0.31</td><td>0.78</td><td>4.18</td><td>5.53</td><td>100.02</td></tr><tr><td>0.25</td><td>0.46</td><td>3.25</td><td>5.19</td><td>96.50</td></tr><tr><td>0.28</td><td>0.63</td><td>3.66</td><td>5.52</td><td>93.69</td></tr><tr><td>0.08</td><td>0.60</td><td>4.13</td><td>5.30</td><td>99.20</td></tr><tr><td>0.18</td><td>0.60</td><td>4.07</td><td>4.44</td><td>94.91</td></tr><tr><td>0.21</td><td>0.52</td><td>3.80</td><td>4.68</td><td>99.64</td></tr><tr><td>0.16</td><td>0.47</td><td>3.52</td><td>4.97</td><td>96.62</td></tr><tr><td>0.09</td><td>0.60</td><td>3.85</td><td>4.55</td><td>97.50</td></tr><tr><td>0.18</td><td>0.53</td><td>3.72</td><td>4.95</td><td></td></tr><tr><td>0.09</td><td>0.13</td><td>0.51</td><td>0.51</td><td></td></tr><tr><td>0.15</td><td>1.89</td><td>4.60</td><td>4.60</td><td>90.13</td></tr><tr><td>0.07</td><td>2.75</td><td>5.00</td><td>4.83</td><td>93.79</td></tr><tr><td>0.07</td><td>1.07</td><td>4.85</td><td>4.55</td><td>93.03</td></tr><tr><td>0.18</td><td>2.25</td><td>5.10</td><td>4.88</td><td>93.68</td></tr></table>
Feuille1

<table><tr><td>0.31</td><td>1.30</td><td>5.94</td><td>5.64</td><td>94.63</td></tr><tr><td>0.24</td><td>1.42</td><td>4.75</td><td>5.94</td><td>100.04</td></tr><tr><td>0.23</td><td>2.52</td><td>6.51</td><td>5.24</td><td>94.96</td></tr><tr><td>0.06</td><td>1.73</td><td>5.73</td><td>4.64</td><td>96.39</td></tr><tr><td>0.33</td><td>2.66</td><td>6.70</td><td>5.53</td><td>97.47</td></tr><tr><td>0.06</td><td>2.67</td><td>4.54</td><td>4.17</td><td>96.42</td></tr><tr><td>0.12</td><td>0.86</td><td>5.86</td><td>5.96</td><td>93.62</td></tr><tr><td>0.25</td><td>2.08</td><td>5.88</td><td>5.94</td><td>99.47</td></tr><tr><td>0.17</td><td>1.93</td><td>5.46</td><td>5.16</td><td></td></tr><tr><td>0.10</td><td>0.66</td><td>0.74</td><td>0.63</td><td></td></tr><tr><td>0.50</td><td>0.30</td><td>5.87</td><td>4.43</td><td>97.22</td></tr><tr><td>0.43</td><td>0.32</td><td>6.17</td><td>5.34</td><td>99.12</td></tr><tr><td>0.58</td><td>0.47</td><td>6.25</td><td>4.35</td><td>99.25</td></tr><tr><td>0.59</td><td>0.16</td><td>5.67</td><td>4.73</td><td>97.48</td></tr><tr><td>0.44</td><td>0.28</td><td>6.09</td><td>4.89</td><td>99.25</td></tr><tr><td>0.57</td><td>0.82</td><td>6.26</td><td>5.64</td><td>99.35</td></tr><tr><td>0.51</td><td>1.41</td><td>6.27</td><td>4.63</td><td>99.11</td></tr><tr><td>0.48</td><td>0.79</td><td>5.78</td><td>4.76</td><td>98.49</td></tr><tr><td>0.55</td><td>0.68</td><td>5.94</td><td>5.62</td><td>99.82</td></tr><tr><td>0.47</td><td>0.60</td><td>5.77</td><td>5.54</td><td>99.88</td></tr><tr><td>0.51</td><td>0.58</td><td>6.01</td><td>4.99</td><td></td></tr><tr><td>0.06</td><td>0.37</td><td>0.23</td><td>0.50</td><td></td></tr><tr><td>0.27</td><td>0.63</td><td>4.45</td><td>5.82</td><td>95.68</td></tr><tr><td>0.46</td><td>0.77</td><td>4.42</td><td>5.71</td><td>96.52</td></tr><tr><td>0.32</td><td>0.68</td><td>4.18</td><td>5.82</td><td>95.69</td></tr><tr><td>0.18</td><td>0.84</td><td>4.47</td><td>5.77</td><td>95.14</td></tr><tr><td>0.19</td><td>0.62</td><td>4.25</td><td>5.90</td><td>95.18</td></tr><tr><td>0.14</td><td>0.43</td><td>4.30</td><td>5.58</td><td>96.40</td></tr><tr><td>0.44</td><td>0.99</td><td>3.93</td><td>5.44</td><td>96.47</td></tr><tr><td>0.20</td><td>0.78</td><td>4.41</td><td>5.84</td><td>95.67</td></tr><tr><td>0.28</td><td>0.72</td><td>4.30</td><td>5.74</td><td></td></tr><tr><td>0.12</td><td>0.17</td><td>0.18</td><td>0.15</td><td></td></tr><tr><td>0.48</td><td>1.84</td><td>5.40</td><td>4.19</td><td>96.95</td></tr><tr><td>0.67</td><td>1.98</td><td>5.36</td><td>4.08</td><td>97.77</td></tr><tr><td>0.53</td><td>1.89</td><td>5.12</td><td>4.19</td><td>96.95</td></tr><tr><td>0.39</td><td>2.05</td><td>5.41</td><td>4.13</td><td>96.40</td></tr><tr><td>0.39</td><td>1.48</td><td>5.52</td><td>3.65</td><td>97.04</td></tr><tr><td>0.40</td><td>1.83</td><td>5.19</td><td>4.27</td><td>96.45</td></tr><tr><td>0.24</td><td>1.35</td><td>5.42</td><td>4.80</td><td>97.02</td></tr><tr><td>0.35</td><td>1.64</td><td>5.24</td><td>3.94</td><td>97.65</td></tr><tr><td>0.41</td><td>1.99</td><td>5.35</td><td>4.21</td><td>96.94</td></tr><tr><td>0.51</td><td>1.93</td><td>4.71</td><td>4.32</td><td>97.96</td></tr><tr><td>0.44</td><td>1.80</td><td>5.27</td><td>4.18</td><td></td></tr></table>
Feuille1

<table><thead><tr><th>0.12</th><th>0.23</th><th>0.23</th><th>0.29</th><th></th></tr></thead><tbody><tr><td>4.88</td><td>9.04</td><td>2.63</td><td>0.86</td><td>98.38</td></tr><tr><td>4.93</td><td>9.03</td><td>2.72</td><td>0.85</td><td>99.55</td></tr><tr><td>4.84</td><td>9.36</td><td>2.51</td><td>0.86</td><td>98.80</td></tr><tr><td>4.91</td><td>9.13</td><td>2.61</td><td>0.86</td><td>99.59</td></tr><tr><td>4.88</td><td>9.28</td><td>2.63</td><td>0.84</td><td>98.92</td></tr><tr><td>4.90</td><td>9.23</td><td>2.72</td><td>0.88</td><td>100.11</td></tr><tr><td>4.99</td><td>9.08</td><td>2.95</td><td>0.86</td><td>99.21</td></tr><tr><td>5.03</td><td>9.06</td><td>2.77</td><td>0.86</td><td>98.79</td></tr><tr><td>5.11</td><td>9.05</td><td>2.53</td><td>0.85</td><td>98.72</td></tr><tr><td>5.02</td><td>9.13</td><td>2.83</td><td>0.84</td><td>98.95</td></tr><tr><td>4.95</td><td>9.14</td><td>2.69</td><td>0.86</td><td></td></tr><tr><td>0.09</td><td>0.11</td><td>0.14</td><td>0.01</td><td></td></tr></tbody></table>
<table><thead><tr><th>Tephra</th><th>Site</th><th>Calibrated age BP<br>(2σ)</th></tr></thead><tbody><tr><td>MF1</td><td>Gourgon</td><td>6,752 – 6,559*</td></tr><tr><td>G2</td><td>Gourgon</td><td>10,372 – 10,201*</td></tr><tr><td>G3</td><td>Gourgon</td><td>10,900**</td></tr><tr><td>G4</td><td>Gourgon</td><td>12,453 – 11,817*</td></tr><tr><td>G5</td><td>Gourgon</td><td>13,342 – 13,179*</td></tr><tr><td>G6</td><td>Gourgon</td><td>13,449 – 13,184*</td></tr><tr><td>M1</td><td>Molhiac</td><td>6,396 – 6,278*</td></tr><tr><td>M2</td><td>Molhiac</td><td>10,290**</td></tr><tr><td>M3</td><td>Molhiac</td><td>10,900**</td></tr><tr><td>D1</td><td>Digonnière</td><td>6,175 – 5,920*</td></tr><tr><td>D2</td><td>Digonnière</td><td>9,597 – 9,487*</td></tr></tbody></table>

* radiocarbon dating (table 1)

** age estimated from age depth models (figure 5)