Julie Dabkowski

Nicole Limondin-Lozouet

STUDIED AREA AND SITES OVERVIEW OF FORMER ISOTOPIC DATA FROM THE PLEISTOCENE SITES NEW STABLE ISOTOPE DATA AT SAINT-GERMAIN-LE-VASSON INTERSITE COMPARISONS DISCUSSION: INTERGLACIAL INTENSITIES IN THE PARIS BASIN CONCLUSIONS

Keywords:

Comparison of temperature and humidity during MIS 11 and MIS 5e

INTRODUCTION

Many recent palaeoclimatic studies have focused on Marine Isotopic Stages (MIS) 5e and 11, as they have long been considered, for different reasons, to be the best analog to our modern interglacial [START_REF] Scholar Tzedakis | Interglacial diversity[END_REF][START_REF]   Shakun | An 800-kyr record of global surface ocean δ O and implications for ice volume-temperature coupling[END_REF]Past Interglacials Working Group of PAGES, 2016). For interglacial comparisons, most investigations have focused on long marine or ice core records; fewer archives covering almost continuously interglacial periods are available for continental areas [START_REF] Lang | Interglacial and glacial variability from the last 800 ka in marine, ice and terrestrial archives[END_REF]Past Interglacials Working Group of PAGES, 2016).

Because they are characteristic of wet and temperate periods [START_REF] Pentecost | The quaternary travertine deposits of Europe and Asia Minor[END_REF][START_REF] Pentecost | Travertine[END_REF], calcareous tufas are key archives for studying interglacials. These continental open-air deposits result from calcite precipitation from meteoric waters at ambient temperature [START_REF] Capezzuoli | Decoding tufa and travertine (fresh water carbonates) in the sedimentary record: the state of the art[END_REF] and are thus suitable targets for palaeoclimatic reconstructions, especially from oxygen and carbon stable isotopes [START_REF] Andrews | Palaeoclimatic records from stable isotopes in riverine tufas: synthesis and review[END_REF][START_REF] Dabkowski | Enregistrement des variations climatiques au cours des interglaciaires d'après l'étude des isotopes stables de la calref de tufs calcaires pléistocènes du nord de la France: exemple des séquences de Caours (SIM 5e; Somme) et de La Celle-sur-Seine (SIM 11; Seine-et-Marne)[END_REF]. Furthermore, they routinely host evidence of past environmental conditions via wellpreserved faunal and floral assemblages that, together with calcite, provide supports for various radiometric dating methods (mainly U/Th series and radiocarbon) [START_REF] Dabkowski | High potential of calcareous tufas for integrative multidisciplinary studies and prospects for archaeology in Europe[END_REF].

Tufas are particularly favourable both to the development of molluscan communities and the in situ preservation of their shells, allowing an accurate reconstruction of the progressive forest extension during interglacial periods [START_REF] Preece | Mapping snails in time: the prospect of elucidating the historical biogeography of the European malacofauna[END_REF]. In western Europe, malacological studies undertaken in recent years have already demonstrated a significant decrease in the Holocene forest land snail diversity compared with the Pleistocene (Limondin-Lozouet and [START_REF] Scholar Limondin-Lozouet | Quaternary perspectives on the diversity of land snail assemblages from northwestern Europe[END_REF]. This difference is due to the occurrence within Pleistocene successions of several species with current ranges centred within central and southern Europe, having never reached the westernmost part of Europe during the Holocene.

Using isotopic data from Caours (Somme) and La-Celle-sur-Seine (Seine-et-Marne) respectively assigned to MIS 5e and MIS 11, and previously unpublished data from Saint-Germain-le-Vasson tufa (Normandy) dated to the first half of the Holocene, we investigate climatic similarities or differences between these Pleistocene interglacials and the modern one that may have affected species distribution.

STUDIED AREA AND SITES

General settings

The three sites included in this study are located in the Paris Basin (Fig. 1), which corresponds with most of the northern half of France and is surrounded by the Armorican massif (west), the Massif Central (south), and Vosges and Ardennes (east and northeast).

The Paris Basin comprises mainly post-Triassic carbonate formations [START_REF] Pomerol | Le bassin de Paris[END_REF] that extend north to the London Basin in England. This calcareous bedrock provides calcium (Ca ) and bicarbonate (HCO 3 ) ions that are dissolved and transported by groundwater to springs and rivers where they can precipitate as tufa calcite (CaCO 3 ). The most important aquifer in the Paris Basin is the porous Upper Cretaceous chalk, with numerous secondary and tributary aquifers. Modern meteorological data are from Météo-France stations near the studied sites (Caen, Abbeville, and Melun stations; Table 1). The average annual temperatures are around 11°C at all sites, with seasonal average temperatures around 5°C-6°C in winter (January to March) and 17-18°C in summer (July to September). Average annual precipitation ranges from 676.8 mm at Melun (near La Celle) to 782.6 mm at Abbeville (near Caours). At all sites, precipitation occurs evenly across the year. Saint-Germain-le-Vasson, Caours, and La Celle therefore currently experience similar weather patterns typical of a temperate oceanic climate. Additionally, extrapolations from the Online Isotopes in Precipitation Calculator [START_REF] Bowen | Interpolating the isotopic composition of modern meteoric precipitation: isotopic composition of modern precipitation[END_REF][START_REF] Bowen | The Online Isotopes in Precipitation Calculator[END_REF] provide very similar mean annual δ O values for modern precipitation, around -7.7‰ at each site (Table 2). This confirms that modern rainfall at Saint-Germain-le-Vasson, Caours, and La Celle has the same oceanic source and that there is virtually no continental effect (decrease in the oxygen isotopic values due to the rainout effect throughout the continent; [START_REF] Andrews | Palaeoclimatic records from stable isotopes in riverine tufas: synthesis and review[END_REF] Mean annual extrapolated δ O of modern precipitation extrapolated at the site locations using the Online Isotopes in Precipitation Calculator [START_REF] Bowen | The Online Isotopes in Precipitation Calculator[END_REF].

Two Pleistocene sites

Caours

2+ - Figure 1.
18

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The tufa sequence at Caours, near Abbeville in the Somme basin (Fig. 1, Table 2), covers a surface of several thousand square metres at the confluence of the Scardon and Drucat streams, with an average thickness of 3 to 4 m (Fig. 2). This tufa was mainly formed on the valley slope, fed by perched springs emerging from the Upper Cretaceous chalk, the largest aquifer in the Paris Basin, which provides carbonate to calcite precipitation. Since 2003, interdisciplinary investigations at Caours have resulted in extended stratigraphic descriptions, dating, and palaeoenvironmental reconstructions [START_REF] Antoine | Le tuf de Caours (Somme, France): mise en évidence d'une séquence eemienne et d'un site paléolithique associé[END_REF]. The discovery of several Middle Palaeolithic levels, associated with abundant faunal remains and lithic artefacts, led to archaeological excavations [START_REF] Scholar Locht | Caours "Les Prés[END_REF][START_REF] Locht | Caours, Rapport triennal de fouille programmée[END_REF].

Caours tufa overlies alluvial deposits of the Etouvie Formation (Fig. 2), which is assigned to MIS 6 (Saalian) in the well-known Somme valley terrace system [START_REF] Scholar | Pleistocene fluvial terraces from northern France (Seine, Yonne, Somme): synthesis, and new results from interglacial deposits[END_REF].

According to malacological data, the transition between the cold Saalian and the Eemian interglacial (MIS 5e) is recorded at the base of the sequence in the fluvial silty deposits preceding the tufa [START_REF] Antoine | Le tuf de Caours (Somme, France): mise en évidence d'une séquence eemienne et d'un site paléolithique associé[END_REF]. The chronostratigraphic attribution of the sequence to the Eemian interglacial was largely confirmed by geochronological data (Useries on calcite, optically stimulated luminescence on quartz grains, and Electron Spin Resonance (ESR)/U-series on tooth), giving an average age of 123 ± 3 ka [START_REF] Antoine | Le tuf de Caours (Somme, France): mise en évidence d'une séquence eemienne et d'un site paléolithique associé[END_REF][START_REF] Bahain | ESR/U-series dating of teeth recovered from well-stratigraphically age-controlled sequences from northern France[END_REF][START_REF] Sier | Evidence for the Blake Event recorded at the Eemian archaeological site of Caours, France[END_REF]. Mammal fauna remains preserved in the archaeological levels allow the reconstruction of environments at the time of human occupations and strengthen the continuous record of the environment evolution at Caours based on the malacological succession [START_REF] Antoine | Le tuf de Caours (Somme, France): mise en évidence d'une séquence eemienne et d'un site paléolithique associé[END_REF][START_REF] Scholar Locht | Caours "Les Prés[END_REF]. The latter shows a clear forest maximum that has been demonstrated to be contemporaneous with the MIS 5e optimum through comparison with previously published palaeoclimatic reconstructions from stable isotopes on tufa calcite [START_REF] Dabkowski | Enregistrement des variations climatiques au cours des interglaciaires d'après l'étude des isotopes stables de la calref de tufs calcaires pléistocènes du nord de la France: exemple des séquences de Caours (SIM 5e; Somme) et de La Celle-sur-Seine (SIM 11; Seine-et-Marne)[END_REF][START_REF] Dabkowski | Climatic and environmental dynamic during the Eemian recorded in a northern France tufa (Caours, Somme basin). Comparison with regional records[END_REF]; Fig. 2).

La Celle

La-Celle-sur-Seine (town of Vernou-La-Celle-sur-Seine) is located in the Seine valley, near Moret-sur-Loing (Seine-et-Marne; Fig. 1, Table 2). The tufa developed on the right-hand side of the Seine valley, 2.5 km upstream from its confluence with the Loing River. It was formed from springs located upslope and accumulated as an 8-to 15-m-thick body covering an area of ca. 12.5 ha. In its lower part, the tufa lies on the fluvial deposits of a middle terrace of the Seine (Fig. 3), about 15 m above the modern alluvial plain: its upper part directly overlies the Upper Eocene Calcaire de Champigny (Limondin-Lozouet et al., 2010). This calcareous bedrock is part of the multilayered Champigny aquifer, which comprises different Eocene deposits from the Calcaires de Brie to the Lutetian limestone (Paris stone), above the Upper Cretaceous chalk. The Champigny aquifer was the source of the carbonates feeding La Celle tufa precipitation. New investigations undertaken at La Celle since 2003 combine stratigraphy, palaeontology, dating, and archaeology (Limondin-Lozouet et al., 2006, 2010;[START_REF] Jolly-Saad | Nouvelle étude des empreintes foliaires des tufs holsteiniens de La Celle-sous-Moret (Seine-et-Marne)[END_REF]. The chronological attribution of the tufa to MIS 11 based on its morphological position within the Seine valley terrace system [START_REF] Lautridou | Le fleuve Seine, le fleuve Manche[END_REF] palaeoclimatic reconstructions from stable isotopes on tufa calcite [START_REF] Dabkowski | Enregistrement des variations climatiques au cours des interglaciaires d'après l'étude des isotopes stables de la calref de tufs calcaires pléistocènes du nord de la France: exemple des séquences de Caours (SIM 5e; Somme) et de La Celle-sur-Seine (SIM 11; Seine-et-Marne)[END_REF][START_REF] Scholar Dabkowski | Climatic variations in MIS 11 recorded by stable isotopes and trace elements in a French tufa (La Celle, Seine Valley): climatic variations in MIS 11 in a French tufa[END_REF][START_REF] Scholar Limondin-Lozouet | Palaeoenvironmental dynamics of the MIS 11 interglacial in north-western Europe based on the malacological succession from La Celle (Seine Valley, France): relationship with glacial refugia and palaeobiodiversity[END_REF]. The identification of temperate conditions is reinforced by the occurrence of leaf and fruit prints of Mediterranean taxa (e.g., Buxus, Ficus;[START_REF] Jolly-Saad | Nouvelle étude des empreintes foliaires des tufs holsteiniens de La Celle-sous-Moret (Seine-et-Marne)[END_REF] as well as by records of several thermophilous mammal taxa, including Hippopotamus and Macaca (Limondin-Lozouet et al., 2006). The latter were found associated with Acheulean lithic artefacts that demonstrate human occupation of the site during the climatic optimum (Limondin-Lozouet et al., 2010).

A Holocene site: Saint-Germain-le-Vasson

Saint-Germain-le-Vasson (SGV) is located in Normandy about 15 km south of Caen (Fig. 1, Table 2). The tufa is developed on a platform, less than 500 m from the head of a small dry valley, leading to the right bank of the Laize River. At certain times of the year, water flows from a spring in the lower part of this small valley, but the fossil tufa is now dry, located 200 m east of the present spring and about 10 m higher. The source of the carbonate was probably the Calcaire de Caen, which crops out about 1 km southeast of the site (Limondin-Lozouet and Preece, 2004). This Middle Jurassic formation constitutes a tributary aquifer fed by the Upper Cretaceous chalk aquifer [START_REF] Pomerol | Le bassin de Paris[END_REF][START_REF] Rodet | Karst de la craie et aquifère de Normandie[END_REF].

In the early 2000s, new investigations at SGV provided a stratigraphic description of the 9.5m-high tufa deposit and detailed palaeoenvironmental reconstructions (Limondin-Lozouet and Preece, 2004;[START_REF] Scholar Limondin-Lozouet | Enregistrement des biocènoses de la première moitié de l'Holocène en contexte tufacé à Saint-Germain-le-Vasson (Calvados)[END_REF]. Seven radiocarbon dates (on charcoal, mollusc shells, and wood) provided a coherent chronology that assigns the SGV tufa to the first half of the Holocene, between 9700 ± 90 and 4213 ± 77 C yr BP, while malacological and palynological data confirm the full record of the Atlantic climatic optimum in the sequence [START_REF] Scholar Limondin-Lozouet | Enregistrement des biocènoses de la première moitié de l'Holocène en contexte tufacé à Saint-Germain-le-Vasson (Calvados)[END_REF].

OVERVIEW OF FORMER ISOTOPIC DATA FROM THE PLEISTOCENE SITES

Caours and La Celle geochemical data have been previously published and extensively discussed as records of intra-interglacial climate variations during MIS 5e and 11, respectively [START_REF] Dabkowski | Enregistrement des variations climatiques au cours des interglaciaires d'après l'étude des isotopes stables de la calref de tufs calcaires pléistocènes du nord de la France: exemple des séquences de Caours (SIM 5e; Somme) et de La Celle-sur-Seine (SIM 11; Seine-et-Marne)[END_REF][START_REF] Scholar Dabkowski | Climatic variations in MIS 11 recorded by stable isotopes and trace elements in a French tufa (La Celle, Seine Valley): climatic variations in MIS 11 in a French tufa[END_REF][START_REF] Dabkowski | Climatic and environmental dynamic during the Eemian recorded in a northern France tufa (Caours, Somme basin). Comparison with regional records[END_REF]. This section presents a brief overview of the former stable isotope investigations, including information useful for the following comparison with unpublished Holocene data from SGV (see "New Stable Isotope Data at Saint-Germain-Le-Vasson" and "Discussion"), also shown on Figures 234and in Tables 3 and4. Summaries of stable isotope data from the three tufa sequences discussed in this paper.

Summaries of stable isotope data from the climatic optima at Caours and La Celle.

Both Caours and La Celle sequences were sampled by hand continuously, every 5 cm, with the exception of some coarser layers at La Celle that could not be sampled properly (as units 2 and 9 mainly comprise large reworked tufa blocks; Fig. 3). Sample columns were placed where most of the stratigraphic units are present in order to cover the longest possible time interval (Figs. 3).

At La Celle, the δ O values range between -5.79 and -4.32 ± 0.09‰ (mean value:

-5.00 ± 0.09‰) and δ C values between -12.1 and -7.9 ± 0.3‰ (mean value: -10.1 ± 0.3‰, n = 116; Table 3).

The MIS 5e climatic optimum was clearly identified at Caours in stratigraphic unit 5 by a to the MIS 11 climatic optimum [START_REF] Scholar Dabkowski | Climatic variations in MIS 11 recorded by stable isotopes and trace elements in a French tufa (La Celle, Seine Valley): climatic variations in MIS 11 in a French tufa[END_REF][START_REF] Scholar Limondin-Lozouet | Palaeoenvironmental dynamics of the MIS 11 interglacial in north-western Europe based on the malacological succession from La Celle (Seine Valley, France): relationship with glacial refugia and palaeobiodiversity[END_REF]Fig. 3). Summaries of stable isotope data from this optimum are presented in Table 4 (n = 12).

δ O values range from -5.01 to -4.32 ± 0.09‰ and δ C values from -11.2 to -10.5 ± 0.3‰.

At La Celle, the uppermost unit (unit 1) also stands out from the rest of the sequence, as it records specific, cooler and wetter, climatic conditions associated with molluscan assemblages characterised by more tolerant forest species and grassland molluscs (unit 1; Fig. 3). This forest regression observed at the transition between units 1 and 2 (Fig. 3) could correspond either to the final phase of the deciduous forest or to the last development of the boreal humid forest at the very end of the interglacial period [START_REF] Scholar Limondin-Lozouet | Palaeoenvironmental dynamics of the MIS 11 interglacial in north-western Europe based on the malacological succession from La Celle (Seine Valley, France): relationship with glacial refugia and palaeobiodiversity[END_REF].

NEW STABLE ISOTOPE DATA AT SAINT-GERMAIN-LE-VASSON

Methods

At SGV, the tufa sequence was regularly sampled by hand according to stratigraphy, except for the most indurate units, with maximal thickness of 10 cm for each sample. Sixty-two samples were analysed for carbon and oxygen stable isotope composition, covering the whole tufa sequence in the most complete profile (Borehole 1), up to -946 cm of relative depth from the top (Fig. 4).

As at Caours and La Celle, approximately 1 g of each field-collected sample was sifted to 250 μm, and the fine fraction was cleaned of volatile organic matter by low temperature (< 80°C) oxygen plasma etching for 6 h at 300 W forward power in a Bio-Rad PT 7300 plasma barrel etcher. Subsamples of 100 ± 10 μg of plasma-ashed tufa were then reacted with anhydrous H 3 PO 4 at 90°C, and isotopic ratios of the resulting CO 2 were measured on a Europa Sigma Hybrid with an in-house autosampler at the Stable Isotope Laboratory of the University of East Anglia. Sixty-nine replicate analyses of the laboratory standard gave 2σ precisions of ±0.2‰ for δ O and ±0.5‰ for δ C.

Results

Isotopic data from Saint-Germain-le-Vasson range between -5.7 and -4.9 ± 0.2‰ for δ O (mean value: -5.3 ± 0.2‰; n = 62) and between -10.5 and -7.9 ± 0.5‰ for δ C (mean value:

-9.3 ± 0.5‰; Table 3). Most of the observed variation in both δ O and δ C is small compared with the confidence intervals (Table 3). Consequently, the climatic optimum could not be clearly defined at SGV: molluscs record shaded damp environments characteristic of a dense forest development in a large part of the sequence, and malacological zones are not correlated with any specific events in the stable isotope record that show little or no variation (Fig. 4). A few palynological samples provide assemblages characteristic of the Atlantic, but they are discontinuous (as pollen is only preserved in the most organic layers, which are rare; Limondin-Lozouet et al., 2005; Fig. 4) and do not allow proper delimitation of this period within the sequence, as is the case at Caours and La Celle.

INTERSITE COMPARISONS

When compared with data from other well-dated Late Quaternary (mainly Holocene)

European tufas [START_REF] Andrews | Palaeoclimatic records from stable isotopes in riverine tufas: synthesis and review[END_REF], SGV results appear consistent with those from Belgium

 

continentality and aridity/evaporation effects are low [START_REF] Andrews | Palaeoclimatic records from stable isotopes in riverine tufas: synthesis and review[END_REF]Fig. 5). This suggests that the three sites were part of similar climatic zones despite their age disparity. This assumption is strengthened by our previous comments on the modern weather patterns and rainfall δ O values at each site (Tables 1 and2), showing that SGV, Caours, and La Celle are part of the same temperate oceanic climate zone in the present.

Caours/SGV

Isotopic data from Caours (MIS 5e) and SGV (first half of the Holocene) are plotted together in Figure 6. Two-tailed Student's t-tests on unpaired data gave p-values lower than the 0.05 limit; Caours and SGV are therefore statistically different regarding both δ O and δ C values, although their respective means are similar according to confidence intervals (Table 3). In detail, the δ O values from Caours optimum appear slightly higher (-4.98 ± 0.09‰; Table 4) than those from the entire sequences of Caours and SGV (-5.35 ± 0.09‰ and -5.3 ± 0.2‰, respectively; Table 3). However, they range from -5.21 to -4.76 ± 0.09‰ (Table 4), which partly covers the whole sequence and SGV δ O variability (Fig. 6, Table 3). About a third of the SGV δ O range (37%, represented by 26 of 62 samples) actually overlaps with Caours optimum δ O data (Fig. 6).

Caours δ C values clearly present a narrow range compared with those from SGV (Fig. 6), as shown by their respective standard deviations (0.6 at SGV vs. 0.3 at Caours; Table 3). All carbon isotopic values for Caours are actually lower than the SGV δ C mean value (-9.3 ± 0.5‰). Both with respect to their mean value (-10.9 ± 0.3‰) and range (-11.1 to -10.8; Table 4), Caours optimum δ C values appear lower than those from the rest of the sequence and from SGV (Fig. 6).

La Celle/SGV

Isotopic data from La Celle (MIS 11) and SGV are plotted together on La Celle and SGV show close δ O mean values with respect to confidence intervals (-5.00 ± 0.09‰ and -5.3 ± 0.2‰, respectively; Table 3) but oxygen isotope values from La

Celle have a wider range (resulting in a higher standard deviation: σ = 0.3), especially toward higher values (up to -4.32 ± 0.09‰ compared with a -4.9 ± 0.2‰ maximum at SGV; Fig. 7, Table 3). The climatic optimum at La Celle is recorded by a notably higher mean δ O value than at SGV (-4.65 ± 0.09‰ and -5.3 ± 0.2‰, respectively; Tables 3 and4). Additionally, the δ O values of the La Celle optimum are higher than all SGV values; only 1 of the 12 values assigned to La Celle optimum is actually within the δ O range of SGV (Fig. 7).

Mean carbon isotope values from SGV and La Celle are similar (-9.9 ± 0.5‰ and -10.1 ± 0.3‰, respectively; Table 3). However, the δ C values recorded at La Celle are far lower than those from SGV (down to -12.1 ± 0.3‰ compared with the SGV minimum of -10.5 ± 0.5‰; Table 3). Most of the lowest δ C values from La Celle are actually recorded in the same stratigraphic unit of the sequence (wet and cooler episode in unit 1; Fig. 3), associated with relatively high δ O values (Fig. 7). The La Celle climatic optimum also exhibits more negative δ C values than the rest of the sequence and SGV, having a lower mean value (-11.0 ± 0.3‰; Table 4). Additionally, the La Celle range of δ C values (-11.2 to -10.5 ± 0.3‰; Table 4) does not overlap with the SGV range of δ C values (-10.5 to -7.9 ± 0.5‰; Fig. 4, Table 3). When these two specific clusters of data (from the climatic optimum and from unit 1) are excluded, the La Celle δ C values appear similar to those from SGV (Fig. 7).

DISCUSSION: INTERGLACIAL INTENSITIES IN THE PARIS BASIN

Climatic parameters influencing stable isotopes in modern and Quaternary tufas in Europe have been well identified [START_REF] Andrews | The stable isotope record of environmental and climatic signals in modern terrestrial microbial carbonates from Europe[END_REF][START_REF] Andrews | Palaeoclimatic records from stable isotopes in riverine tufas: synthesis and review[END_REF][START_REF] Dabkowski | Enregistrement des variations climatiques au cours des interglaciaires d'après l'étude des isotopes stables de la calref de tufs calcaires pléistocènes du nord de la France: exemple des séquences de Caours (SIM 5e; Somme) et de La Celle-sur-Seine (SIM 11; Seine-et-Marne)[END_REF]. Tufa calcite δ O is directly linked to local airmass composition, which depends mainly on its source, rainout effects due to continentality or processes such as the amount effect, and changes in the atmospheric temperature [START_REF] Andrews | Stable isotopic compositions of Recent Figure 8.   freshwater cyanobacterial carbonates from the British Isles: local and regional environmental controls[END_REF][START_REF] Andrews | The stable isotope record of environmental and climatic signals in modern terrestrial microbial carbonates from Europe[END_REF]. As noted earlier, the three studied sites are part of the same climatic area (i.e., under the influence of the same airmass), and no continental effect is observed in the present-day rainfall δ O.

Furthermore, under oceanic climate, precipitation occurs evenly across the year as currently recorded at meteorological stations near the studied sites, while isotopically anomalous rainfall events are unlikely to be recorded in well-mixed groundwater because of long-term homogenisation within most, and especially large, aquifers [START_REF] Darling | Hydrological factors in the interpretation of stable isotopic proxy data present and past: a European perspective[END_REF], like the chalk and limestones of the Paris Basin. In addition, the three studied tufas, formed in close proximity to the springs, are unlikely to have been affected by processes such as evaporation. Consequently, the differences in the δ O of studied sites must reflect differences in atmospheric temperature: higher δ O values corresponding to warmer conditions [START_REF] Andrews | Palaeoclimatic records from stable isotopes in riverine tufas: synthesis and review[END_REF]. On the other hand, tufa calcite δ C is influenced by biomass type/abundance and rainfall amount (i.e., moisture availability), which control the relative contribution of two distinct sources of carbonate into the precipitating water. Under wetter conditions, well-developed vegetation and soils provide low δ C, while increasing rainfall leads to shorter groundwater residence time within the aquifer and, in turn lower dissolution of the marine carbonate with typical higher δ C: increasing moisture availability thus results in lower δ C [START_REF] Andrews | Palaeoclimatic records from stable isotopes in riverine tufas: synthesis and review[END_REF].

MIS 5e versus the Holocene

The comparison of isotopic data from Caours and SGV suggests that MIS 5e did not experience different temperature conditions than the first half of the Holocene (including the Atlantic optimum), although its optimum would have known slightly warmer conditions (higher δ O values; Fig. 6). On the other hand, the discrepancies observed in carbon isotope data suggest: (1) that MIS 5e had moisture conditions similar to the wettest conditions recorded during the first half of the Holocene, but with apparently smaller amplitudes of variations; and (2) that the MIS 5e climatic optimum was wetter than the first half of the Holocene (including the Atlantic optimum). However, parallel analyses of Mg/Ca and Sr/Ca ratios in calcite, which are mainly influenced in tufa by the amount of precipitation [START_REF] Garnett | Climatic change recorded by stable isotopes and trace elements in a British Holocene tufa[END_REF], show that increasing moisture conditions at Caours was due more to vegetation/soil development than to strictly climatic (rainfall) variations [START_REF] Dabkowski | Climatic and environmental dynamic during the Eemian recorded in a northern France tufa (Caours, Somme basin). Comparison with regional records[END_REF].

At Caours, the malacological faunal list is clearly characteristic of an interglacial and includes several forest species originating from central Europe and that are thus beyond their modern range (Limondin-Lozouet and Preece, 2014). However, no specific species or biome suggests that environmental/climatic conditions were significantly warmer or wetter than during the Holocene [START_REF] Antoine | Le tuf de Caours (Somme, France): mise en évidence d'une séquence eemienne et d'un site paléolithique associé[END_REF][START_REF] Limondin-Lozouet | Successions malacologiques à la charnière Glaciaire/Interglaciaire: du modèle Tardiglaciaire-Holocène aux transitions du Pleistocène[END_REF]. Large mammal remains preserved in archaeological levels at Caours mainly belong to red deer (Cervus elephus), fallow deer (Dama dama), and aurochs (Bos primigenius). Other large herbivores are also present but occur less frequently (Dicerorhinus hemitoechus, Equus sp., Capreolus capreolus, Sus scrofa), as do Ursus arctos and Aonyx antiqua. These species are characteristic of interglacial conditions during the middle Pleistocene and the beginning of the late Pleistocene [START_REF] Antoine | Le tuf de Caours (Somme, France): mise en évidence d'une séquence eemienne et d'un site paléolithique associé[END_REF][START_REF] Scholar Locht | Caours "Les Prés[END_REF]. None indicate particularly warm and wet conditions compared with the Holocene. These palaeoenvironmental data are thus consistent with our observations based on stable isotope comparisons.

In northwestern Europe, only a few continental records have provided long-term quantitative climate reconstructions for MIS 5e. The lacustrine sequence of La Grande Pile in the Vosges (Fig. 1) has been the reference record for the Paris Basin since the 1970s and has supported numerous palaeoenvironmental studies mainly based on pollen, chironomids, and Coleoptera [START_REF] Woillard | Grande Pile peat bog: a continuous pollen record for the last 140,000 years[END_REF][START_REF] Scholar De Beaulieu | The last climatic cycle at La Grande Pile (Vosges, France). A new pollen profile[END_REF][START_REF] Ponel | Rissian, Eemian and Würmian Coleoptera assemblages from La Grande Pile (Vosges, France)[END_REF][START_REF] Scholar Cheddadi | Was the climate of the Eemian stable? A quantitative climate reconstruction from seven European pollen records[END_REF]. Coleoptera assemblages, and especially quantitative reconstructions of seasonal temperatures by the mutual climatic range method, suggest that the MIS 5e optimum at La Grande Pile was slightly warmer than today and possibly wetter [START_REF] Ponel | Rissian, Eemian and Würmian Coleoptera assemblages from La Grande Pile (Vosges, France)[END_REF][START_REF] Scholar Ponel | 110000 years of Quaternary beetle diversity change[END_REF]. More recently, reconstructions of annual and seasonal temperatures and precipitation combining pollen and organic matter δ C data have been obtained from a new core covering part of MIS 5 (130-100 ka), including MIS 5e [START_REF] Rousseau | Reconstruction of the Grande Pile Eemian using inverse modeling of biomes and δ C[END_REF][START_REF] Rousseau | Estimates of temperature and precipitation variations during the Eemian interglacial: new data from the grande pile record (GP XXI)[END_REF].

Despite two short cool events that might not be recorded at Caours due to sedimentary hiatuses [START_REF] Dabkowski | Climatic and environmental dynamic during the Eemian recorded in a northern France tufa (Caours, Somme basin). Comparison with regional records[END_REF], mean annual climatic conditions similar to those of the present day are recorded at La Grande Pile during the Eemian. However, the climatic optimum at La Grande Pile appears slightly warmer and is characterised by a significant increase in mean annual precipitation. These data are consistent with the similar temperature and moisture conditions recorded during MIS 5e at Caours compared with SGV data. In addition, the mean annual precipitation signal shows no particular trend or  

variation after the climatic optimum at La Grande Pile, which appears consistent with apparently stable conditions reflected by the low variability of the δ C at Caours during MIS 5e (Fig. 2) compared with the Holocene (SGV; Fig. 4).

Farther east, at Gröbern in central Germany (Fig. 1), seasonal temperatures and mean annual precipitation during the Eemian were reconstructed using a multivariate probabilistic method on pollen and plant microfossil assemblages and indicate warmer conditions (especially during summer) than today and a relatively low level of mean annual precipitation [START_REF] Kühl | Eemian and Early Weichselian temperature and precipitation variability in northern Germany[END_REF]. However, this site is located in an area presently characterised by a strong continental climate, which may explain the discrepancies with our data from the Paris Basin. Different regional climatic responses to global variations during MIS 5e have indeed been suggested by the comparison of several terrestrial pollen sequences across western Europe [START_REF] Sánchez Goñi | Increasing vegetation and climate gradient in Western Europe over the Last Glacial Inception (122-110 ka): data-model comparison[END_REF].

Regional quantitative climate reconstructions are also provided from a Bay of Biscay core

MIS 11 versus the Holocene

Comparison of δ O variability of La Celle and SGV (Fig. 7) suggests that temperatures were similar to warmer during MIS 11 than during the first half of the Holocene. However, climatic conditions during the MIS 11 climatic optimum appear notably warmer compared with those during the first half of the Holocene (including the Atlantic optimum).

Regarding moisture availability, carbon isotopic data show that MIS 11 was mostly comparable to the first half of the Holocene, except during the climatic optimum and during the last phase recorded at La Celle (unit 1; Fig. 3), which both appear to have been wetter. The latter is also characterised by relatively cooler conditions (Fig. 7).

The strong consistency between the stable isotope variations and the malacological succession of La Celle has already been demonstrated in previous publications [START_REF] Dabkowski | Enregistrement des variations climatiques au cours des interglaciaires d'après l'étude des isotopes stables de la calref de tufs calcaires pléistocènes du nord de la France: exemple des séquences de Caours (SIM 5e; Somme) et de La Celle-sur-Seine (SIM 11; Seine-et-Marne)[END_REF][START_REF] Scholar Dabkowski | Climatic variations in MIS 11 recorded by stable isotopes and trace elements in a French tufa (La Celle, Seine Valley): climatic variations in MIS 11 in a French tufa[END_REF]. The La Celle molluscan record is characterised by the recognition of the "Lyrodiscus fauna," which mainly comprises forest species, including taxa currently having central and southern European ranges [START_REF] Rousseau | West-European terrestrial molluscs assemblages of isotopic stage 11 (Middle Pleistocene): climatic implications[END_REF][START_REF] Rousseau | The continental record of stage 11: a review[END_REF][START_REF] Scholar Limondin-Lozouet | Palaeoenvironmental dynamics of the MIS 11 interglacial in north-western Europe based on the malacological succession from La Celle (Seine Valley, France): relationship with glacial refugia and palaeobiodiversity[END_REF].

Palaeobotanical data, especially leaf and fruit prints of Buxus and Ficus, suggest warmer conditions at the time of La Celle tufa deposition (Limondin-Lozouet et al., 2006;[START_REF] Jolly-Saad | Nouvelle étude des empreintes foliaires des tufs holsteiniens de La Celle-sous-Moret (Seine-et-Marne)[END_REF]. Furthermore, the occurrences of Macaca sylvanus and Hippopotamus [START_REF] Scholar De Beaulieu | Reconstruction of Middle Pleistocene   palaeoenvironments based on pollen and stable isotope investigations at Val-de-Lans, Isère, France[END_REF][START_REF] Reille | Pollen analytical biostratigraphy of the last five climatic cycles from a long continental sequence from the Velay region (Massif Central, France)[END_REF]. However, quantitative reconstructions based on Coleoptera from La Côte indicate that the MIS 11 climatic optimum was particularly warm [START_REF] Field | Middle Pleistocene deposits at La Côte, Val-de-Lans, Isère department, France: plant macrofossil, palynological and fossil insect investigations[END_REF], as observed at La Celle. In a comparison of several MIS 11 continental records, especially from Europe, most indicate higher humidity than during the Holocene, but in temperature reconstructions, either similar or warmer conditions are reported across locations [START_REF] Rousseau | The continental record of stage 11: a review[END_REF].

CONCLUSIONS

In globally significant records (e.g., from marine and ice cores), MIS 5 and 11 are the strongest interglacials of the last 800 ka, marked by higher sea levels, reduced ice sheets, higher atmospheric CO 2 , and finally, higher temperatures (Lang and Wolff, 2011; Past [START_REF] Pentecost | The quaternary travertine deposits of Europe and Asia Minor[END_REF][START_REF] Scholar Limondin-Lozouet | Quaternary perspectives on the diversity of land snail assemblages from northwestern Europe[END_REF]. Most exceptions occur in Thuringia (Germany), where partly fault-controlled cooled geothermal springs (i.e., partly independent of climatic conditions) fed massive tufa deposits (or "travitufa," according to [START_REF] Capezzuoli | Decoding tufa and travertine (fresh water carbonates) in the sedimentary record: the state of the art[END_REF]) also during MIS 7 and 9 (e.g., Ehrinsdorf [MIS 7] and a part of the Bilzingsleben deposit [MIS 9], which is however mainly assigned to MIS 11; [START_REF] Mania | La stratigraphie et le Paléolithique du complexe saalien dans la région de la Saale et de l'Elbe[END_REF]. Tufa deposits have been shown to require temperate and, especially, wet climatic conditions [START_REF] Pentecost | Travertine[END_REF][START_REF] Capezzuoli | Decoding tufa and travertine (fresh water carbonates) in the sedimentary record: the state of the art[END_REF], although they can start growing very quickly after the onset of such conditions, as demonstrated for the last climatic cycle by many late-glacial/Early Holocene tufas [START_REF] Pentecost | The quaternary travertine deposits of Europe and Asia Minor[END_REF][START_REF] Dabkowski | The late-Holocene tufa decline in Europe: myth or reality?[END_REF]. Therefore, the most frequent occurrence of MIS 5e and 11 tufas suggests that, in Europe, these interglacials must have been stronger, in terms of temperature and/or moisture availability, than MIS 7 and 9.

As tufas provide favourable (calcareous) conditions for both the development and preservation of molluscan communities [START_REF] Preece | Mapping snails in time: the prospect of elucidating the historical biogeography of the European malacofauna[END_REF], mollusc shells are usually well represented in quantity and quality within fossil deposits. Several European tufas have thus provided detailed assemblages comparable to those from Caours and La Celle (Fig. 8). As noted earlier, MIS 11, 5, and 1 are the best documented Pleistocene interglacials for malacological records from tufa deposits. During Pleistocene interglacials, the total number of land snails and of forest species systematically exceeds those observed during the Holocene (Limondin-Lozouet and Preece, 2014). Additionally, the highest malacological diversity is always recorded at MIS 11 sites (Fig. 8). In the studied area, the MIS 11 malacological assemblages include up to 41 species of forest molluscs, 50% of which are non-indigenous (out of range or extinct). Among these, a quarter are species originating from southern Europe. The occurrence of some strictly Mediterranean species during the optimum phase is a specificity of MIS 11 malacofaunas [START_REF] Scholar Limondin-Lozouet | Palaeoenvironmental dynamics of the MIS 11 interglacial in north-western Europe based on the malacological succession from La Celle (Seine Valley, France): relationship with glacial refugia and palaeobiodiversity[END_REF].

Such variations in molluscan diversity are likely related to differences in climatic parameters and in particular to higher moisture availability during MIS 5e and especially MIS 11 compared with the Holocene, which is consistent with our conclusions based on palaeoclimatic data from Caours, La Celle, and SGV. Unfortunately, few or no isotopic data are yet available from other Pleistocene tufas in Europe to further support these observations.

Number of forest land snails recorded in tufa deposits from Germany, France, and southern England (for site location, see Fig. 1).

Tufa stable isotopes therefore seem appropriate for comparing climatic conditions prevailing during the Holocene and Pleistocene interglacials, especially MIS 5 and MIS 11.

Data from La Celle, Caours, and SGV suggest that in the Paris Basin:

• most of MIS 11, and especially its optimum, was wetter and warmer than the Holocene and MIS 5e;

• although weaker than MIS 11, MIS 5e experienced wetter conditions than the Holocene, especially during the optimum, but no clear difference is observed in terms of temperature, except for the climatic optimum that might have been slightly warmer during MIS 5e.

New investigations on recent and Pleistocene tufa deposits from France, Germany, England, and elsewhere in Europe should lead to a more complete record of differences and similarities between interglacials and would allow discussion of differences in interglacial climatic patterns at the European scale.

  Location map of Saint-Germain-le-Vasson (SGV), Caours, and La Celle (in red) and other tufa sequences and interglacial European records discussed in this paper.

  observed from the westernmost site, Saint-Germain-le-Vasson, to the easternmost, La Celle. Modern climatic data recorded at Météo-France meteorological stations near the studied sites (data from 1981 to 2010). Site coordinates and elevation.

  Overview of stratigraphic and isotopic data from previous investigations at Caours: (A) Long transect along the slope made by combining observations from several boreholes, cores, and stratigraphic sections and showing the fluvial terrasse (gravel and silts) underlying the chalk, the tufa deposit, and posterior slope deposits (modified after Antoine et al., 2006), as well as the position of the sampling column. (B) Details of the stratigraphy of the "East profile 2007" at the sampling column position and a summary of palaeoclimatic (tufa calcite δ O and δ C) and palaeoenvironmental information (modified after Dabkowski et al., 2016).

  Overview of stratigraphic and isotopic data from previous investigations at La Celle: (A) Drawing of the long profile showing sandy to silty fluvial deposits (units 16-14) underlying the Champigny limestone (unit 17), the tufa deposit (units 13-1), and the position of the sampling column. (B) Details of the stratigraphy at the sampling column position and a summary of palaeoclimatic (tufa calcite δ O and δ C) and palaeoenvironmental information (modified after Limondin-Lozouet et al., 2010; Dabkowski et al., 2012).

  was reinforced by new palaeontological evidence (occurrence of the malacological "Lyrodiscus assemblage") and several radiometric dates (U/Th thermal ionization mass spectrometry on calcite and ESR-U/Th on tooth enamel) suggesting an age around 400 ka[START_REF] Bahain | ESR/U-series dating of teeth recovered from well-stratigraphically age-controlled sequences from northern France[END_REF][START_REF] Limondin-Lozouet | Successions malacologiques à la charnière Glaciaire/Interglaciaire: du modèle Tardiglaciaire-Holocène aux transitions du Pleistocène[END_REF]

  Figure 2.

  [START_REF] Scholar Limondin-Lozouet | Palaeoenvironmental dynamics of the MIS 11 interglacial in north-western Europe based on the malacological succession from La Celle (Seine Valley, France): relationship with glacial refugia and palaeobiodiversity[END_REF]. The malacological succession allowed detailed palaeoenvironmental reconstruction showing the progressive development of forest biotopes with a clear maximum correlated to the MIS 11 climatic optimum (Fig.3), as shown by comparison with

  Overview of previous investigation atSaint-Germain-le-Vasson (SGV) and unpublished geochemical data: (A) Map of the tufa quarry at SGV showing the position of the different boreholes and stratigraphic sections. (B) Stratigraphic correlations of the profiles studied showing the development of the tufa deposits over nearly 10 m (modified after Limondin-Lozouet and Preece, 2004). (C) Detail of the highest stratigraphic profile (Borehole 1), position of the geochemical samples, and summaries of palaeoenvironmental (after Limondin-Lozouet et al., 2005) and palaeoclimatic (tufa calcite δ O and δ C) information.

  2 and 3). A total of 59 and 117 samples were analysed at Caours and La Celle, respectively. Measurement of oxygen and carbon isotopic ratios was performed at the Stable Isotope Laboratory of the University of East Anglia (UK) using the same protocol described later for SGV; replicate analyses of the laboratory standard (n = 75) gave 2σ precision of ±0.09‰ for δ O and ±0.3‰ for the δ C. The stable isotope results for Caours range from -5.21 to -4.76 ± 0.09‰ for δ O (mean value: -5.35 ± 0.09‰; n = 59) and from -11.1 to -10.8 ± 0.3‰ for δ C (mean value: -10.1 ± 0.3‰; n = 59; Table

  14

  Figure 4.

  Figure 5.

  Combined δ O and δ C values for Caours and Saint-Germain-le-Vasson (SGV).

Figure 7 .

 7 Two-tailed Student's t-tests on unpaired data gave p-values below the 0.05 threshold, suggesting that both δ O and δ C values are statistically different between La Celle and SGV. It may be noted that the same tests performed on the Caours and La Celle data also gave a p-value lower than 0.05 for δ O but p = 0.6 for δ C, suggesting that there is no statistical difference in the carbon isotope variability of the Pleistocene sites. Combined δ O and δ C values for La Celle and Saint-Germain-le-Vasson (SGV).

  Figure 6.

(

  MD99-2227; Fig.1) applying the modern analog technique to high-resolution pollen data: they indicate that the warmest period of the Eemian was significantly warmer than the present day in terms of temperatures of the warmest month(Sanchez Goni et al., 2012).These higher temperatures are contemporaneous with fast development of forest cover in Europe during the Eemian; the increase in temperate forest pollen percentages is twice as large and rapid at the onset of the Eemian compared with the Holocene. Such rapid development of forest environments would have significantly increased the contribution of soil and vegetation to tufa δ C at Caours and may explain the low values recorded during the optimum compared with the rest of the sequence and with Holocene data from SGV (Fig.6).

  contemporaneous with the climatic optimum(Limondin-Lozouet et al., 2006, 2010) indicate very temperate and wet conditions, respectively. All these palaeoenvironmental data strengthen the observations based on stable isotope comparison. There are few continental records providing climatic reconstructions back to MIS 11 in western Europe. The closest to La Celle are lacustrine records in the French Massif Central (Le Velay) and in the Vercors (La Côte; Fig. 1), whose pollen assemblages suggest similar climatic conditions during MIS 11 and the Holocene (de Beaulieu et al.

Table

Table 2 . 1 18

 2

Table 3 .Table 4 .

 34 maximum diversity of molluscs (including the widest range of forest species;[START_REF] Antoine | Le tuf de Caours (Somme, France): mise en évidence d'une séquence eemienne et d'un site paléolithique associé[END_REF] contemporaneous with maximal temperature and humidity conditions recorded by geochemical proxies[START_REF] Dabkowski | Climatic and environmental dynamic during the Eemian recorded in a northern France tufa (Caours, Somme basin). Comparison with regional records[END_REF] Fig. 2). Summaries of δ O and δ C data attributed to this climatic optimum are presented in Table4(n = 4). They range respectively from -5.21 to -4.76 ± 0.09‰ and from -11.1 to -10.8 ± 0.3‰.At La Celle, a maximum in diversity and number of forest species, correlated with wetter and warmer conditions, is similarly observed in stratigraphic unit 7 and has been assigned

	18	13
	18
	13
	18
	13
		 

  Interglacials Working Group of PAGES, 2016). It is noteworthy that most Pleistocene tufa deposits known in western Europe and providing reliable palaeoenvironmental data are assigned to one of these two interglacials

	13
	13
	18
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Acknowledgments

We thank both reviewers for their useful comments on the article. This paper is a contribution to the ANR project NEANDROOTS.

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