Didier Néraudeau
email: didier.neraudeau@univ-rennes1.fr

Jean-Paul Saint

Simona Saint-Martin

Laurent Jeanneau

Jean-David Moreau

Philippe Marc

France Polette

Damien Gendry

John Brunet

Jérôme Tréguier

Amber

Simona Saint

Marc Philippe

Amber-and plant-bearing deposits from the Cenomanian of Neau (Mayenne, France)

Keywords: Palynology, Gymnosperm cuticles, Cheirolepidiaceae, Sheated bacteria, Amber, Cenomanian, France Palynologie, Cuticules de gymnospermes, Cheirolepidiaceae, Bactéries gainées, Ambre, Cénomanien, France

Introduction

Late Cretaceous amber deposits are well distributed in western France, from the Anjou and Sarthe regions, at the North, (Ecommoy locality in Girard et al., 2013aGirard et al., , 2013b; Hucheloup locality in [START_REF] Fleury | Palaeobotanical investigation of a Cenomanian clay lens in Hucheloup quarry, Maine-et-Loire, NW France: taxonomic, stratigraphic and palaeoenvironmental implications[END_REF] to the Aude department, at the South (Fourtou locality in Girard et al., 2013aGirard et al., , 2013b; see [START_REF] Moreau | Albian flora from Archingeay-Les Nouillers (Charente-Maritime): comparison and synthesis of Cretaceous meso-and macro-remains from the Aquitaine Basin (southwestern France)[END_REF], for a synthetic map of mid-Cretaceous french amber deposits). The more numerous amber deposits and the more rich in amber are located in the Charentes region, where Cenomanian sands and clays with lignite have been studied in several quarries, road works and coastal outcrops [START_REF] Néraudeau | Un nouveau gisement à ambre insectifère et à végétaux (Albien terminal probable) : Archingeay (Charente-Maritime, France)[END_REF][START_REF] Néraudeau | Découverte d'un dépôt paralique à bois fossiles, ambre insectifère et restes d'Iguanodontidae (Dinosauria, Ornithopoda) dans le Cénomanien inférieur de Fouras (Charente-Maritime, sud-ouest de la France)[END_REF][START_REF] Néraudeau | Stratigraphie et paléontologie (plantes, vertébrés) de la série margino-littorale Albien terminal À Cénomanien basal de Tonnay-Charente (Charente-Maritime, France)[END_REF][START_REF] Néraudeau | A new amber deposit from the Cretaceous (uppermost Albian-lowermost Cenomanian) of SW France[END_REF]. Conversely, amber from Mayenne has been the less studied. The only previous works were made by [START_REF] Durand | Découverte d'un dépôt cénomanien fossilifère à Neau (Mayenne)[END_REF] about the discovery of a karst filling of fossiliferous Cenomanian lignites and sands in a substratum of Cambrian limestones at Neau, and by [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF] who performed a palynological analysis of the sediment. The latter study described lower to mid Cenomanian assemblages dominated by gymnosperm pollen grains and fern spores, and marked by the progressive increase of angiospermous forms. Finally, the rare mentions of Cenomanian amber at Neau have been provided by [START_REF] Durand | Découverte d'un dépôt cénomanien fossilifère à Neau (Mayenne)[END_REF], and the few available data were then cited by other authors, such as Girard et al. (2013aGirard et al. ( , 2013b)). We present here the first synthesis dedicated to the Cenomanian amber from Neau and its associated botanical macro-, meso-and microremains, along with palaeoenvironmental and stratigraphic considerations.

2 Material and methods

Field observations

The Neau quarry is located at about 30 km NW from Laval in the department of Mayenne, NW France (Fig. 1). The quarry is exploited by the Society Chaux & Dolomie Françaises/ Lhoist France Ouest for the extraction of Cambrian dolomitic limestones and the production of lime.

At the top of the Cambrian limestones, several dissolution cavities are filled by Cenomanian erosive deposits (Figs. 2 and3). According to the field observations made by the authors, the base of the karsts corresponds generally to a few metres of lignitic sand and clay (CnL facies on Figs. 2A and3) including large pieces of fossil wood (trunk and branches fragments). The top of the karst filling consists of one to two metres of white sand (CnS facies on Figs. 2A and3A-B), more or less oxidized and coloured in yellow at the contact with the lignite. Both Cambrian limestone palaeoreliefs and karsts are covered by discordant glauconitic sands (CnG facies on Figs. 2A and3A-B) including more or less kaolinitic lenses. The base of lignitic deposits contains pyritised foraminifers that testify the coastal marine origin of these sediments [START_REF] Durand | Découverte d'un dépôt cénomanien fossilifère à Neau (Mayenne)[END_REF]. The marine remains disappear at the top of the Cenomanian sandy deposits. The presence of kaolinite indicates a typical lateritic weathering anterior to the Cenomanian [START_REF] Durand | Découverte d'un dépôt cénomanien fossilifère à Neau (Mayenne)[END_REF]. One sample of lignitic clay has been collected at the top of the facies CnL in the main karst (Fig. 3A-B), for palynological analyses. In addition, seven samples recovered from Neau amber-rich lignitic clay in 1972, and 39 corresponding palynological slides prepared and analyzed by [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF] were reexamined to complete our palynological analyses and to compare our biostratigraphical and palaeobotanical conclusions (samples S2, S3, S4, S7, S9, S11, S12 on Fig. 2B).

The amber can be collected by sieving of the lignites, but can also be sometimes collected on the outcrop surface after washout by the rain. The lignites and amber studied in this paper were collected during a field trip organized on June 4th 2014 by the Museum of Laval (J. Tréguier) and the University of Rennes I (D. Néraudeau), completed by additional collections made by John Brunet and D. Gendry.

2.2 Amber, wood and cuticle preparation (Fig. 4) Tiny amber grains have been collected by sieving of the lignitic clay, and then separated from wood and cuticle fragments (Fig. 4A). The lignitic marl was soaked in a solution of hydrogen peroxide (12%) and water for a few days. The disaggregated sediment was then washed with tap water through a column of sieves (2.0 mm, 1.0 mm and 0.5 mm meshes). The pieces of ambers as well as fossil plants (Fig. 4B-H) were picked out by naked eye or under a stereomicroscope Leica 125. Photographs were taken with a BMS digital USB camera (5 megapixels). Specimens are housed in the collections of the University of Rennes 1 under numbers IGR-PAL-2828 and IGR-PAL-22829 for the wood fragments and IGR-PAL-2830 to IGR-PAL-2836 and IGR-PAL-2844/IGR-PAL-2845 for the plant cuticles. An amber lot is housed under number IGR-PAL-2843. Amber slides used to illustrate the amber inclusions correspond to numbers IGR-PAL-2837 to IGR-PAL-2842. The amber grain containing wood fragments studied in the paper corresponds to number IGR-PAL-2846.

In the lignitic clay, plant remains are greatly disarticulated and vary in size including meso-to macro-remains (Fig. 4B-H). They consist of leafy axes (Fig. 4B-E) and cone scales of conifers (Fig. 4F) as well as fragmented leaves of ginkgophytes (Fig. 4G,H). Wood fragments are also abundant (Fig. 4A). The collection includes hundreds of plant specimens. They are preserved as coalified compressions with or without cuticles. Some plant microremains (pollen, woods) were also found as inclusions inside amber.

In order to characterize the amber grains, thin sections were prepared with a thickness slightly greater than the standard thickness of the petrographic thin section. The optical microscope used is a Zeiss Axioscope 40 with photographing device and observations were made with Â5 and Â10 objectives for large observation. The observations under confocal laser scanning microscope (CLSM) were essentially performed on a Leica TCS SP5 microscope. The images obtained allow viewing of the autofluorescent objects in false colours. 3D reconstruction was obtained by acquisition of stacks of closely spaced confocal optical sections at 0.10 mm to 0.20 mm intervals. Then these images were treated for optimization with the open source software Image J (Rasband, 1997(Rasband, -2013)). Amber and wood examinations with Scanning Electron Microscope (SEM) were performed with the Hitachi SU3500 model.

In addition to the micro-fragments of wood found by sieving of the lignitic clay (Fig. 4A), several large pieces of trunk and branches have been collected during the field trip at the surface of the outcrop (Fig. 3B).

Amber analyses

Two pieces of Neau amber, an opaque and milky denoted form A and a translucent and orange denoted form B and a yellowish Baltic amber as reference were analyzed by thermally assisted hydrolysis and methylation (THM) also called thermochemolysis. Small portions of amber were crushed manually in an agate mortar. The powders (∼0.1 mg) were heated with TMAH (Tetramethylammonium Hydroxyde) at 400°C. THM was carried out using a Frontier Lab PY-2020iD pyrolyser coupled with a Shimadzu GCMS-QP2010 Plus system operating with a split ratio of 100. Separation was achieved using a capillary column SLB-5MS (60 m  0.25 mm ID, 0.25 mm film thickness) with the carrier gas He with a flow of 1.1 mL/min. The operating conditions were as follows: initial temperature held at 50 °C for 2 minutes, increased to 310 °C at a rate of 4 °C/min for 34 minutes. Individual compounds were identified based on comparison of (i) MS data with the NIST2014 library and literature [START_REF] Anderson | The nature and fate of natural resins in the geosphere-IV. Middle and Upper Cretaceous amber from the Taimyr Peninsula, Siberia-evidence for a new form of polylabdanoid of resinite and revision of the classification of Class I resinites[END_REF][START_REF] Anderson | New evidence concerning the structure, composition, and maturation of class I (Polylabdanoid) resinites. In: Amber, Resinite, and Fossil Resins[END_REF][START_REF] Anderson | The nature and fate of natural resins in the geosphere. XII. Investigation of C-ring aromatic diterpenoids in Raritan amber by pyrolysis-GC-matrix isolation FTIR-MS[END_REF][START_REF] Dutta | Terpenoid composition and botanical affinity of Cretaceous resins from India and Myanmar[END_REF][START_REF] Otto | Biomarkers of Holocene buried conifer logs from Bella Coola and north Vancouver, British Columbia, Canada[END_REF]) and (ii) retention time with the reference Baltic amber.

The relative distribution of identified compounds was determined by measuring the area of a specific fragment, denoted m/z integration in Table 1. The peak area of the selected m/z for each compound was integrated and corrected by a mass spectra factor (Tab. 1) calculated as the reciprocal of the proportion of the fragment used for the integration and the entire fragmentogram. The molecular ratios were calculated using those corrected areas that allow an approximation of areas on the total ion chromatogram while preventing from the integration of co-eluting compounds.

Palynomorphs

Seven samples were recovered from Neau amber-rich lignitic clay in 1972, and 39 corresponding palynological slides were prepared and analyzed by [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF]S2, S3, S4, S7, S9, S11, S12, see Fig. 2B). Because their study focused on several Cenomanian localities of western France, [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF] chose not to discuss extensively the palaeoenvironmental implications and the age attribution of the palynological assemblages of Neau. The palynomorphs illustrated are not accompanied by coordinates, and one cannot know which pollen grain or spore comes from Neau or from another locality. Thus, in order to determine more precisely the palaeoenvironmental and stratigraphic modalities associated with the formation/deposit of Neau resin À and later amber À, those 39 slides were reexamined, and the corresponding results are presented herein.

Several slides now correspond to partly dried residue, rendering observations difficult, but all seven samples yielded palynological assemblages, however often small. If the sample and corresponding slides were not particularly rich, all palynomorphs were counted and identified, as it is the case for S2 (N = 132), S7 (N = 27), S9 (N = 23), S11 (N = 135), and S12 (N = 106). The two remaining samples S3 and S4 provided rich assemblages. Three hundred palynomorphs were counted and identified, but all the palynomorphs were observed in order to log potential infrequent forms (Appendix S1). The 39 slides are housed in the collections of the University of Rennes 1 under numbers Cd1 to Cd39. Description. The material consists of isolated internodes constituting the leafy axes (Fig. 4B-D). The internodes are never connected. They are elongated, flattened, up to 13.0 mm long, and up to 3.5 mm wide. Each internode is formed by one whorl of three proximally fused leaves. Free parts of the leaves are only visible distally (Fig. 4B-E). They form three tiny tips which are triangular in shape, broader than long, up to 1.0 mm long, and up to 2.5 mm wide and show an obtuse apex (Fig. 4E). Surface of internodes shows numerous longitudinal rows of stomata.

Remarks. Cellular characters of the stomata are not preserved. Frenelopsis is one of the most abundant conifers from the Cenomanian deposits of Western France. This taxon was reported from many areas in Aude, Charente-Maritime, Vienne and Maine-et-Loire (see synthesis in Moreau et al., 2017 and references therein).

Family Incertae sedis

Cone scale Type 1 (Fig. 4F) Table 1. List of identified compounds and their relative proportions in Neau ambers. Target compounds were identified based on m/z int and m/z identification. Areas were integrated using the m/z int, and the area on the total ion chromatogram was estimated using the mass spectra factor (MSF). Non-detected compounds are denoted "n.d.".

No.

Compound name m/z identification m/z int MSF Form A Form B 2,3,4,4a,7,8,4a, Material. One specimen, IGR-PAL-2834.

Description. The scale is longer than wide (i.e., 4.5 mm long and 3 mm wide), convex, shows an acuminate base, a broad truncate apex and an entire margin (Fig. 4F). The base displays a long free stalk (2.5 mm long and up to 1.5 mm wide). The adaxial surface displays several central and proximal grooves. They end before the truncate apex.

Remarks. The preservation is not sufficient to unambiguously identify the presence of ovule scars. Some isolated ovulate cone scales were previously reported from the lower Cenomanian of western France, in Charente-Maritime (e.g., [START_REF] Néraudeau | Amber, plant and vertebrate fossils from the Lower Cenomanian paralic facies of Aix Island (Charente-Maritime, SW France)[END_REF]. They were tentatively ascribed to Alvinia bohemica (Velen.) J. Kvaček. However, the shape of the cone scale from Mayenne differs from these specimens.

Ginkgoales

Family Karkeniaceae Genus Eretmophyllum Eretmophyllum obtusum (Velen.) J. [START_REF] Kvaček | New data and revision of three gymnosperms from the Cenomanian of Bohemia-Sagenopteris variabilis (Velenovsk y) Velenovsk y, Mesenea bohemica (Corda) comb. n. and Eretmophyllum obtusum (Velenovsk y) comb. n[END_REF] 2,3,4,4a,5,8,4a, Description. The material consists of up to 20 mm long and up to 11 mm wide fragmented lamina (Fig. 4G-H). The leaves are coriaceous and entire-margined. The apices are obtuse. Base of leaves and petiole are not preserved. The veins are dichotomously branched and run subparallel to leaf lamina and converge near the apex (Fig. 4G-H). The dichotomies form narrow angles. In the medial part, lamina display up to 12 parallel veins. The veins are up to 0.3 mm wide and are regularly spaced. Cuticle is heavily cutinized. Cuticle displays costal and intercostal bands, both bearing stomata apparatuses. Leaves are amphistomatic. Stomata are randomly oriented, scattered, and particularly abundant in intercostal bands (Fig. 5A). Stomata are haplocheilic, sunken and surrounded by 4 to 6 subsidiary cells (Fig. 5C-F). The diameter of stomatal apparatuses varies from 40 to 70 mm. The stomatal pits show a round or oval shape. Ordinary epidermal cells are square, rectangular, or polygonal, 20-110 mm long and form longitudinal rows. The anticlinal walls of ordinary epidermal cells are straight to slightly sinuous (Fig. 5B). Numerous rounded and spindle-shaped resin bodies are dispersed in the mesophyll (Fig. 5G). Rounded ones are up to 0.5 mm in diameter whereas spindle-shaped ones are up to 1.1 mm long (Fig. 5H-J).

Remarks. [START_REF] Pons | Nouvelles études paléobotaniques des environs d'Angers I. Eretmophyllum andegavense nov. sp., ginkgoale fossile du Cénomanien[END_REF] erected the species Eretmophyllum andegavense D.Pons, Boureau et Broutin based on material from the Cenomanian of Angers (western France). However, the distinction of Eretmophyllum (Velen.) J.Kvaček with Nehvizdya Hlu stík is debated for a long time. [START_REF] Kvaček | New data and revision of three gymnosperms from the Cenomanian of Bohemia-Sagenopteris variabilis (Velenovsk y) Velenovsk y, Mesenea bohemica (Corda) comb. n. and Eretmophyllum obtusum (Velenovsk y) comb. n[END_REF] transfered Nehvizdya to the genus Eretmophyllum, and introduced a new combination, Eretmophyllum obtusum (Velen.) J. Kvaček. However, [START_REF] Gomez | A new species of Nehvizdya (Ginkgoales) from the Lower Cretaceous of the Iberian Ranges (Spain)[END_REF] attempted to distinguish Eretmophyllum from Nehvizdya on the basis of the presence or absence of papillae on subsidiary cells as the differential character. [START_REF] Gomez | A new species of Nehvizdya (Ginkgoales) from the Lower Cretaceous of the Iberian Ranges (Spain)[END_REF] tentatively transferred the species Eretmophyllum andegavense in the genus Nehvizdya. However, as pointed by [START_REF] Kvaček | A new Late Cretaceous ginkgoalean reproductive structure Nehvizdyella gen. nov. from the Czech Republic and its whole-plant reconstruction[END_REF] the differential character used by [START_REF] Gomez | A new species of Nehvizdya (Ginkgoales) from the Lower Cretaceous of the Iberian Ranges (Spain)[END_REF] is not acceptable being variable among genera in the Ginkgoales. Here, we follow [START_REF] Kvaček | A new Late Cretaceous ginkgoalean reproductive structure Nehvizdyella gen. nov. from the Czech Republic and its whole-plant reconstruction[END_REF] who suggested that Nehvizdya and Eretmophyllum cannot be splitted only based on the "papillae" argument. Although several studies [START_REF] Gomez | Assemblages floristiques de l'Albien-Cénomanien de Charente-Maritime (SO France)[END_REF][START_REF] Gomez | Diversity and histology of a plant litter bed from the Cenomanian of Archingeay-Les Nouillers (southwestern France)[END_REF][START_REF] Néraudeau | Stratigraphie et paléontologie (plantes, vertébrés) de la série margino-littorale Albien terminal À Cénomanien basal de Tonnay-Charente (Charente-Maritime, France)[END_REF] reported Nehvizdya andegavense from the Albian-Cenomanian of several localities in Charente-Maritime, we agree with [START_REF] Fleury | Palaeobotanical investigation of a Cenomanian clay lens in Hucheloup quarry, Maine-et-Loire, NW France: taxonomic, stratigraphic and palaeoenvironmental implications[END_REF] who used Eretmophyllum rather than Nehvizdya for material from the Cenomanian of western France (Maine et Loire).

Palynomorphs from the lignitic clay

The seven palynological samples yielded a fairly diverse palynoflora composed of 71 species and ca. 1000 specimens (Appendix S1). Abundance charts of the five richest samples show that the proportion between spores (Fig. 6C-L) and pollen grains (Fig. 6M-Z) is well balanced, but spores are often slightly dominant (Fig. 6A). They usually represent around 60% of the assemblage, but can go up to 92% for S4. Most abundant spores correspond to Gleicheniidites senonicus (Gleicheniaceae), to smooth walled forms associated with the genera Cyathidites and Deltoidospora, and to massive cicatricose spores of Appendicisporites and Cicatricosisporites (Anemiaceae; Fig. 6A, E-J). Appendicisporites insignis (Fig. 6I-J) is the most common form of ornamented spores. Among subsidiary spores are those of the Lycophytes, mostly belonging to Camarozonosporites (Fig. 6D), a few bryophitic forms (Fig. 6C), spores associated with the Osmundaceae, such as Baculatisporites (Fig. 6K), and spores of uncertain botanical affinities, like Patellasporites tavaredensis (Fig. 6L) and Microreticulatisporites sacalii.

Gymnosperm pollen grains (Fig. 6M-O) are dominated by Circumpolles (Classopollis torosus) and small inaperturate or monoaperturate grains associated with the Cupressaceae (incl. Taxodiaceae), including Exesipollenites tumulus, Inaperturopollenites dubius, and Taxodiaceaepollenites hiatus (Fig. 6A). On the contrary, bisaccates (mostly Pinaceae/ Podocarpaceae, Fig. 6M) and grains of Araucariaceae (Araucariacites, Fig. 6N) were rarely encountered, and seldom represent more than 5% of the assemblages, except for the youngest assemblage (Fig. 6A).

While the different groups of spores and gymnosperms pollen grains display a fairly fluctuant abundance throughout the five assemblages, S11 and S12 are marked by the sudden increase of angiosperm pollen grains (Fig. 6A). They represent from 3-5% of S2-S4 to 12-15% of S11-S12. Numerous representatives of Dichastopollenites were observed (uncertain affinity), as well as tricolpate (Tricolpites, Fig. 6V), tricolporate (Nyssapollenites, Fig. 6U), and tricolpoidate (Phimopollenites, Fig. 6X-Z) forms belonging to the Eudicots. Grains of Phimopollenites were particularly diversified and abundant. Less common forms include Stellatopllis cf. largissimus (Fig. 6S) and Artiopollis indivisus (Fig. 6T). No normapolles were observed. Very few dinocysts were logged in the oldest assemblages, mostly belonging to Surculosphaeridium longifurcatum (Fig. 6B). Except for the progessive increase of the abundance of the angiosperm pollen grains, and the curious abundance peak of Glecheiniidites in S4, no particular trend is noticed from S2 to S12, and the resulting interpretation will therefore consider the "Neau palynoflora" as a whole.

4 Amber characteristics 4.1 General aspect (Figs. 7 and8)

The collected amber grains are of variable appearance and size. Large pieces of amber are very uncommon and have been collected at the surface of the outcrop. They range from 1 to 3 cm in size. Three varieties of colour have been observed: milky brown (Fig. 7A), translucent honey (Fig. 7B) and opaque cork colour (Fig. 7C-D). A few ones are empty (Fig. 7D). The size of tiny amber grains collected by clay sieving varies generally from a few millimetres to one centimetre (Fig. 8A). Then, the appearance of the grains depends on the shape of the original resin drops or their posterior fragmentation, during transport or the conditions of deposit and sampling. Thus, the best preserved grains correspond to fine, more or less cylindrical flows or rather spherical drops with an attachment point. Others result from a more complex flow and show several protuberances. If some grains appear translucent with a dominant orange-yellow colour, very many grains are wholly or partly opaque with earthy or cork colours of beige to brown (Figs. 4A and8A). The opacity is very irregularly distributed according to the grains appearance (Fig. 8B-E) corresponding to several phenomena: presence of bubbles and/or emulsions more or less coarse, colonization by filamentous microorganisms (Fig. 8H) or a conjugation of both (Fig. 8B,I). The external appearance revealed by the SEM observations shows that cracks are often present on the surface of the amber grains (Fig. 8F). In some cases the superposition of resin flows is clearly visible (Fig. 8G).

4.2 Plant microremains included inside amber 4.2.1 Vegetal fibers and wood (Fig. 9)

The size of the large pieces of wood collected on the outcrop varies from several centimetres to about 1 m, and numerous ones show Teredo-borings typical for coastal marine environments in transgressive settings [START_REF] Gingras | Modern perspectives on Teredolites Ichnofacies: observations from Willapa Bay, Washington[END_REF], and tiny borings of unknown origin (Teredo, insect attacks?) (Fig. 9A,B). SEM observations of the wood fragments included in the amber evidenced pitting on the radial tracheid walls, preserved as pit chamber inner casts (Fig. 9C,D). While some up to 9 pits long row of contiguous pits occurred (Fig. 9D), locally pit rows seems to be interrupted (Fig. 9C). The regularity of the spacing between the preserved pits, however, argues more for non-preservation than for absence of pits. Consequently the tracheid radial pitting was interpreted as araucarian. The cross-fields are of the araucarioid type, with 5 to 7 contiguous alternate cupressoid oculipores (Fig. 9E). The fragmentary material did not allow to study growth-ring features, nor the occurrence or resin canals or axial parenchyma. According to these limited morphological observations, the most probable taxa are (from the most probable to the least one) (1) Agathoxylon; (2) Brachyoxylon;

(3) Ginkgoxylon. The fact that these wood pieces are included in the amber could indicate that the resin producers were Araucariacae or Cheirolepidiaceae. These are indeed the only wood genera yet reported from the Mesozoic and combining araucarioid cross-fields and at least partly araucarian radial tracheid pitting [START_REF] Philippe | A key to morphogenera used for Mesozoic conifer-like woods[END_REF].

All these three genera are known to produce resin inside their tracheids [START_REF] Philippe | Bois fossiles du Jurassique de Franche-Comté (nord-est de la France) : systématique et biogéographie[END_REF], and the three of them were reported from the Cenomanian of Western France [START_REF] Perrichot | Environnements paraliques à ambre et végétaux du Crétacé Nord-Aquitain (Charentes, Sud-Ouest de la France)[END_REF]. The first and xylologically most probable one, Agathoxylon, was reported associated to all ambers with the same provenance. Despite its etymology genus Agathoxylon is not necessarily a univocal evidence of the Araucariaceae. After this has been suspected several times, it has recently been shown that Agathoxylon wood can also occur in Cheirolepidiaceae (Steart et al., submitted). Brachyoxylon is usually considered as related to the Cheirolepidiaceae (Macchour and Pons, 1995) and Ginkgoxylon to the Ginkgoalean [START_REF] Jiang | A Jurassic wood that provides insights into the earliest steps in Ginkgo wood evolution[END_REF]. Here in Neau, according to the non-woody remains all the three taxa occur (i.e. Araucariaceae, Cheirolepidiaceae and Ginkgoalean). The amber-embedded fragment of wood therefore does not make it possible to specify the taxonomic origin of this amber.

Pollen grains included in amber (Fig. 10)

Examination of some thin sections revealed the presence of gymnosperm pollen grains belonging to the genus Classopollis, which is associated with the extinct family of the Cheirolepidiaceae [START_REF] Balme | Fossil in situ spores and pollen grains: an annotated catalogue[END_REF][START_REF] Schrank | Pollen and spores from the Tendagru Beds, Upper Jurassic and Lower Cretaceous of southeast Tanzania: palynostratigraphical and paleoecological implications[END_REF]Fig. 10). They are often arranged in clusters (Fig. 10A-B, F), but isolated grains were also observed (Fig. 10C-D). Their rimula is discrete, but discernable. [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF] found numerous Classopollis grains within the lignitic clay of Neau, that they all identified as a new species called Classopollis tenuiparietalis. However, they state that C. tenuiparietalis is morphologically identical to the Aptian and Cenomanian Portuguese taxon Classopollis obidosensis Groot and Groot, creating this new form only to accommodate Cenomanian French pollen grains. Classopollis tenuiparietalis is thus considered invalid. As the morphological differences between C. obidosensis, C. classoides Pflug, and C. torosus (Reissinger), Couper are very tenuous, we consider them all synonymous of the first form described, Classopollis torosus (see diagnoses of Couper, 1958, pp. 156-157, and[START_REF] Groot | Plant microfossils from Aptian, Albian and Cenomanian deposits of Portugal[END_REF]Groot, 1962, p. 161). This latter species is then adopted for the pollen grains from Neau amber.

Trapped palynomorphs have been mostly recovered from Eocene Baltic amber [START_REF] Wetzel | Amber-and plant-bearing deposits from the Cenomanian of Neau (Mayenne, France)[END_REF][START_REF] Arnold | Vergessene Einschlüsse-Blütenstaub in baltischem Bernstein[END_REF]see Langenheim and Bartlett, 1971 for 1800s and early 1900s references). A few other studies on subsidiary Cenozoic amber bearing strata have also documented spores and pollen grains in Eocene amber from France [START_REF] Breton | Land and freshwater microflora in a Sparnacian amber from the Corbières (South France): first observations[END_REF][START_REF] De Franceschi | Extraction du pollen inclus dans l'ambre [Sparnacien du Quesnoy (Oise), bassin de Paris] : vers une nouvelle spécialité de la paléo-palynologie[END_REF][START_REF] Dejax | Le contenu cellulaire du pollen fossilisé dans l'ambre, préservé à l'état organique[END_REF], and Miocene amber from Peru and Mexico (Langenheim in Poinar, 1992, p. 78;[START_REF] Antoine | Amber from western Amazonia reveals Neotropical diversity during the middle Miocene[END_REF]. Mesozoic records are scarce, and concerns exclusively Cretaceous strata. Angiospermous pollen grains and spores were apparently recovered from Lower Cretaceous Lebanese amber, but neither precise reference nor illustrations are provided [START_REF] Azar | Lebanese amber[END_REF][START_REF] Engel | The earliest earwigs in amber (Dermaptera): a new genus and species from the Early Cretaceous of Lebanon[END_REF]Whalley in Poinar, 1992, p. 161). Several clusters of gymnosperm and angiosperm pollen grains were recovered from the Cenomanian Myanmar amber, always observed in association with various insects [START_REF] Poinar | Cascoplecia insolitis (Diptera: Cascopleciidae), a new family, genus, and species of flower-visiting, unicorn fly (Bibionomorpha) in Early Cretaceous Burmese amber[END_REF][START_REF] Cai | Beetle Pollination of Cycads in the Mesozoic[END_REF][START_REF] Grimaldi | Direct evidence for eudicot pollen-feeding in a Cretaceous stinging wasp (Angiospermae; Hymenoptera, Aculeata) preserved in Burmese amber[END_REF][START_REF] Lin | Life habits and evolutionary biology of new two-winged long-proboscid scorpion flies from mid-Cretaceous Myanmar amber[END_REF][START_REF] Hinkelman | A Myanmar amber cockroach with protruding feces contains pollen and a rich microcenosis[END_REF]. In Europe, Monsulcites grains were observed within late Albian amber from Spain [START_REF] Peris | False Blister Beetles and the expansion of gymnosperm-insect pollination modes before Angiosperm dominance[END_REF]. The Classopollis clusters described herein are the first pollen grains documented from Mezosoic French amber so far.

Microinclusions

The amber of Neau contains various inclusions of microorganisms (Saint Martin et al., under study) initial resin results of the complete opacification of the amber grains (Figs. 7C,D,8E,I,), and often of black colouring of the peripheral parts of the amber drops, just below the crust surface (Fig. 7D). These microinclusions are very widespread in Cretaceous ambers [START_REF] Schmidt | Leptotrichites resinatus new genus and species: a fossil sheathed bacterium in Alpine Cretaceous amber[END_REF][START_REF] Martin | Exquisite preservation of a widespread filamentous microorganism from French Cretaceous ambers: a key for review of controversial fossil[END_REF]. Smaller clumps of actinomycetes are also found to a lesser extent, located on the periphery of the amber grains.

Chemical characteristics

The total ion chromatograms of the THM-GC-MS analysis of the Neau resins are illustrated in Figure 11. The relative proportions of (i) the different categories of compounds and (ii) labdanoid diterpenes and compositional ratios are given in Table 2. The molecular fingerprint was composed of 66 molecules from three main families: (i) labdanoid diterpenes produced by the thermochemolysis of the A/B ring system of a polylabdanoid structure, (ii) methyl(hydro)naphthalene and methylphenanthrene and (iii) tricyclic diterpenes. Both pieces of ambers produced a different chemical fingerprint. Most of the compounds (80%) occurred in both fingerprints, but in different relative proportions.

Labdanoid diterpenes are the main chemical group in form A (64% of the analyzed compounds), while they only represent 20% of the analyzed compounds in form B (Tab. 2). The similarity of the retention times of the carboxylic acids compared with Baltic amber and the absence of dimethyl succinate classified these samples as Class Ib ambers. Labdanoid diterpens of form A are dominated by bicyclic acids (66%) with a large predominance of C 15 over C 14 (SC 14 / SC 15 = 0.23). In form B, they are dominated by 1-methylbicyclic hydrocarbons (64% of labdanoid diterpens) with a slight predominance of C 15 over C 14 (SC 14 /SC 15 = 0.88).

Methyl(hydro)naphthalene and methylphenanthrene are the main chemical group in form B (64% of analyzed compounds), while they represent 21% of the analyzed compounds in form A. This group included trimethylindene, ionene, methylionene and diagenetic products of sesqui-and diterpenoids. The distribution of these compounds is quite similar in both form with the predominance of 5 isomers of trimethylnaphthalene (38 and 36% in form A and B, respectively) and 2 isomers of dimethylnaphthalene (17 and 13% in form A and B, respectively). Amberene was detected in low amount in the program of form B and represented 0.5% of this chemical group. The third chemical category was composed of tricyclic diterpenes. In form A, this group was dominated by methyl 16,17-dinordehydroabietate (23%), dimethylphenanthrene (19%) and methyl 8-abieten-18-oate (15%) with low occurrence of callitrisic acid derivatives. In form B, this group was dominated by dimethylphenanthrene (32%), methyl dehydroabietate (13%) and the isomers of trimethylphenanthrene (12%). Methyl callitrisate (5% and methyl 16,17-dinorcallitrisate (1%) were also detected.

Discussion

Singularity of the amber from Neau

The appearance of the Cenomanian amber of Neau is very similar to that of the amber grains generally collected in many Cretaceous French amber deposits of various ages. The same reduced size and the drop shape of the best preserved grains can be found in other Cenomanian French sites: e.g. Poitou (Valentin et al., this volume), Sarthe [START_REF] Breton | Les microorganismes de l'ambre cénomanien d'Ecommoy (Sarthe, France)[END_REF][START_REF] Breton | La bioaccumulation de microorganismes dans l'ambre : analyse comparée d'un ambre cénomanien et d'un ambre sparnacien, et de leurs tapis algaires et bactériens[END_REF]Girard et al., 2013aGirard et al., , 2013b)). This feature is also common for the Turonian of Dordogne (Saint Martin et al., 2013aMartin et al., , 2013b;;[START_REF] Néraudeau | Palaeontology of the upper Turonian paralic deposits of the Sainte-Mondane Formation, Aquitaine Basin, France[END_REF] and Aude [START_REF] Breton | L'ambre turonien du ruisseau des Tarquès (Commune de Duilhac-sous-Peyrepertuse, Aude, France)[END_REF], the Santonian of Provence (Saint [START_REF] Martin | Filamentous micro-organisms in Upper Cretaceous amber (Martigues, France)[END_REF]Martin et al., , 2013;;[START_REF] Martin | Exquisite preservation of a widespread filamentous microorganism from French Cretaceous ambers: a key for review of controversial fossil[END_REF]Frau et al., this volume;Saint Martin et al., this volume), and the Campanian of Aude [START_REF] Breton | L'ambre campanien du Mas d'Azil (Ariège, France) : gisement, microinclusions, taphonomie[END_REF]. On the other hand, they do not correspond to amber samples taken from the Albo-Cenomanian of Charente Maritime or the Upper Cretaceous from Vendée, where large nodules can be found [START_REF] Néraudeau | A new amber deposit from the Cretaceous (uppermost Albian-lowermost Cenomanian) of SW France[END_REF][START_REF] Girard | Microcénoses des ambres médio-crétacés français. Taphonomie, systématique, paléoécologie et reconstitution du paléoenvironnement[END_REF][START_REF] Néraudeau | Upper Cretaceous amber from Vendée, north-western France: Age dating and geological, chemical, and palaeontological characteristics[END_REF].

Consequently, like in Dordogne, Poitou or Provence ambers, the very small size of the amber drops from Neau did not favour the preservation of arthropod inclusions as large amber drops from the Charentes and Vendée did. The only micro-inclusions that have been observed in the amber from Neau correspond to filamentous organisms such as sheathed bacteria and actinomycetes. But other micro-organisms, such as amoeba or diatoms seem to be lacking.

Conversely, palynological inclusions, which were never observed in French Cretaceous ambers, are well preserved in Neau amber (see Sect. 4.2.2). The lack of palynomorphs, known to be resistant to physical and chemical taphonomical processes, is difficult to explain for the other Cretaceous French ambers. Their presence in the Mayenne amber could be related to a season of resin flow more contemporaneous to the conifer pollination. [START_REF] Langenheim | Interpretation of pollen in amber from a study of pollen in present-day coniferous resin[END_REF] have noticed that the probability of finding pollen in amber can be increased when pollen was produced throughout the entire period of resin secretion. However, they also observed that several genera of palynomorphs were trapped throughout the year within resin, regardless of either time of pollination and period of resin production. As Cretaceous palynomorphs have been generally noticed when they are found in association with insects and plants (see Sect. 4.2.2), it could be possible that spores and pollen grains were trapped within other Cretaceous amber, but were not observed because they were not in the vicinity of larger fossils. However, the researches of [START_REF] Girard | Microcénoses des ambres médio-crétacés français. Taphonomie, systématique, paléoécologie et reconstitution du paléoenvironnement[END_REF]Girard ( ), (2013Girard ( , 2018) ) and Saint [START_REF] Martin | Filamentous micro-organisms in Upper Cretaceous amber (Martigues, France)[END_REF]Martin et al. ( , 2013aMartin et al. ( , 2013b) ) dedicated to the identification of every microinclusions in French Cretaceous ambers devoid of arthropod inclusions, have never observed pollen grains in these ambers, in spite of their diversity of geographical (centre-western, south-western or south-eastern France) and stratigraphical (Albian, Cenomanian, Turonian, Santonian, Campanian) origins. The case of Lebanese amber shows another original situation, the pollen grain species trapped in the Lower Cretaceous Hammana amber lacking in the palynological assemblage of the sediment containing the amber [START_REF] Azar | Lebanese amber[END_REF].

The chemical fingerprints of form A and B ambers composed of labdanoid diterpenes produced, methyl(hydro)naphthalene, methylphenanthrene and tricyclic diterpenes is typical of Cretaceous ambers [START_REF] Anderson | The nature and fate of natural resins in the geosphere. XII. Investigation of C-ring aromatic diterpenoids in Raritan amber by pyrolysis-GC-matrix isolation FTIR-MS[END_REF][START_REF] Bray | The nature and fate of natural resins in the geosphere XIII: a probable pinaceous resin from the early Cretaceous (Barremian), Isle of Wight[END_REF][START_REF] Menor-Salván | The molecular composition of Cretaceous ambers: Identification and chemosystematic relevance of 1,6-dimethyl-5-alkyltetralins and related bisnorlabdane biomarkers[END_REF][START_REF] Nohra | Chemical characterization and botanical origin of French Ambers[END_REF]. Both chemical fingerprints shared 80% of the detected compounds and the 66 analyzed molecules fall in the three aforesaid chemical classes. Based on the higher proportion of methyl (hydro)naphthalene and methylphenanthrene [START_REF] Clifford | A new rapid technique for the characterization of lignin in vascular plants: thermochemolysis with tetramethylammonium hydroxide (TMAH)[END_REF] and lower SC14/SC15 [START_REF] Clifford | The nature and fate of natural resins in the geosphere. IX Structure and maturation similarities of soluble and insoluble polylabdanoids isolated from Tertiary Class I resinites[END_REF], the differences in the chemical fingerprints could be interpreted as a higher degree of maturation for form B than for form A. However both come from the same deposit, so the same diagenetic conditions could be assumed. Since 80% of the molecules are common to both fingerprints, a similar botanical precursor may be assumed. In such a situation, the differences between both fingerprints could be due to the initial composition of the resin that can present large seasonal and inter-specific variations [START_REF] Langenheim | Plant resins: chemistry, evolution, ecology, and ethnobotany[END_REF] and/or from heterogeneities in the physicchemical conditions of the deposit.

The chemical fingerprint of form A is characterized by (i) the predominance of labdanoid diterpenes with a predominance of bicyclic acids and (ii) the occurrence of tricyclic diterpenes coming from dehydroabietic and callitrisic acids with a predominance of dehydroabietic acid derivatives. It is similar to that described for the Cretaceous amber from the Raritan formation [START_REF] Anderson | The nature and fate of natural resins in the geosphere. XII. Investigation of C-ring aromatic diterpenoids in Raritan amber by pyrolysis-GC-matrix isolation FTIR-MS[END_REF] that has been assigned to the Cupressaceae. However the vegetal macrofossils from Neau are not from this family. Moreover the chemical fingerprint of the Cretaceous amber from Vendée (France) assigned to the Cupressaceae is characterized by a large predominance of callitrisic acid derivatives over dehydroabitic acid derivatives [START_REF] Nohra | Chemical characterization and botanical origin of French Ambers[END_REF].

Bisnorsimonellite also occurred in form A. The chemical fingerprint of this form A is similar to that described for the Charentese (France) Cretaceous amber [START_REF] Nohra | Chemical characterization and botanical origin of French Ambers[END_REF]. The chemical fingerprint of the form B is characterized by the occurrence of traces of amberene and by a higher proportion of 16,17,18-trisnorabieta-8,11,13-triene versus 18-norabietatriene. It is similar to that described for the type 2 Cretaceous ambers from Spain [START_REF] Menor-Salván | The molecular composition of Cretaceous ambers: Identification and chemosystematic relevance of 1,6-dimethyl-5-alkyltetralins and related bisnorlabdane biomarkers[END_REF]. The extinct family Cheirolepidiaceae has been suggested as the potential producer of these ambers, which is in accordance with the vegetal macrofossils associated with the Neau ambers. Consequently Neau ambers may be assigned to the Cheirolepidiaceae.

The present data reinforce the chemical signature suggested for the ambers produced by the extinct family Cheirolepidiaceae. The combination of previous observations [START_REF] Bray | The nature and fate of natural resins in the geosphere XIII: a probable pinaceous resin from the early Cretaceous (Barremian), Isle of Wight[END_REF][START_REF] Menor-Salván | The molecular composition of Cretaceous ambers: Identification and chemosystematic relevance of 1,6-dimethyl-5-alkyltetralins and related bisnorlabdane biomarkers[END_REF][START_REF] Nohra | Chemical characterization and botanical origin of French Ambers[END_REF] and the present data suggests the following chemical fingerprint: (i) occurrence of labdanoid diterpenes, (ii) occurrence of tricyclic diterpenes coming from dehydroabietic and callitrisic acids with a predominance of dehydroabietic acid derivatives, (iii) a higher proportion of 16,17,18-trisnorabieta-8,11,13-triene versus 18-norabietatriene (Tab. 2), (iv) absence or occurrence in low proportion of amberene and (v) occurrence of ferruginol or its diagenetic products such as bisnorsimonellite.

Age of the lignitic clay(s)

Despite the revealing title of their study, [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF] did not consider all the palynological assemblages they observed to be mid-Cenomanian in age. This is the case of the palynoflora recovered from Neau, which they interpreted as lower to mid Cenomanian. They based their age attribution (1) on the presence of the same species of Classopollis in the clays of both Neau and Ecommoy, the latter being unequivocally mid-Cenomanian, and (2) on the absence of the form Lobelina, which would be indicative of an Albian age (Azema et al., 1972, p. 10). However, we consider herein that the specimens identified as Classopollis belong to the long-ranging form C. torosus (see Sect. 3.2). Moreover, the Circumpolle genus Lobelina created by [START_REF] Médus | Contribution à la classification des grains de pollen du groupe des Circumpolles (Pflug) Klaus[END_REF] was later proven to be a nomen nudum [START_REF] Jansonius | Genera File of Fossil Spores and Pollen. 3287 cards[END_REF], and is considered as a form of Classopollis. In any case, the use of Circumpolles to date Mesozoic deposits has not been proven satisfactory in spite of Médus efforts to produce a comprehensive morphologic and stratigraphic identification key [START_REF] Médus | Contribution à la classification des grains de pollen du groupe des Circumpolles (Pflug) Klaus[END_REF]. Thus, to confirm the age attribution made by [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF], supplementary palynological arguments must be made.

Several observations support a Cenomanian rather than Albian age for the lignitic clays of Neau. The presence of Artiopollis indivisus (Fig. 6T) is worth being noted, this form having been observed only in Late Cretaceous palynofloras so far, especially Cenomanian [START_REF] Singh | Cenomanian microfloras of the Peace River area Northwestern Alberta[END_REF][START_REF] Ravn | The palynostratigraphy of the Dakota Formation (?Late Albian-Cenomanian) in its type area, northwestern Iowa and northeastern Nebraska, USA[END_REF][START_REF] Lupia | Discordant morphological disparity and taxonomic diversity during the Cretaceous angiosperm radiation: North American pollen record[END_REF]. The occurring of Microreticulatisporites sacalii is sometime considered as a stratigraphic argument in favour of a Cenomanian age [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF] because it has been almost exclusively found within Cenomanian strata [START_REF] Deák | Microfossiles organiques » du Wealdien et du Cénomanien dans un sondage de Charente-Maritime[END_REF][START_REF] Médus | Le Cénomanien supérieur de la coupe de Laudun (Gard, France) : étude palynologique et données sédimentologiques[END_REF][START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF], but [START_REF] Ravn | Miospores from the muddy sandstone (upper Albian), wind river basin, Wyoming, USA[END_REF] observed this species in late Albian assemblages of Wyoming. If this form is frequently encountered, it may be considered as relatively stratigraphically significant, when coupled with other stratigraphic arguments. The observation of numerous tricolpoidate and tricolporate forms, such as Phimopollenites and Nyssapollenites, is also indicative of Cenomanian rather than Albian assemblages. Specimens belonging to those genera, and more generally tricolporate pollen grains, appear very scarcely during the Albian, but become much more frequent and diverse during the Cenomanian [START_REF] Doyle | Angiosperm pollen zonation of the continental Cretaceous of the Atlantic coastal plain and its application to deep wells in the Salisbury Embayment[END_REF][START_REF] Hochuli | Timing of early angiosperm radiation: recalibrating the classical succession[END_REF]. Actually, those tricolpoidate and tricolporate specimens were encountered more frequently in the palynoflora from Neau than in the lower Cenomanian palynofloras recovered from Charente-Maritime, Charente, and Vienne [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF][START_REF] Polette | Palynological assemblage from the lower Cenomanian plant-bearing Lagerstätte of Jaunay-Clan Ormeau-Saint-Denis (Vienne, western France): stratigraphic and paleoenvironmental implications[END_REF]. The absence of indubitable mid-Cenomanian markers, such as Normapolles, has to be acknowledged. The lack of observation does not necessarily mean that Normapolle grains were not present in Neau palynoflora, and the absence of a form cannot be considered as stratigraphically significant. However, Normapolles complex diversified quite rapidly from the end of mid Cenomanian onward [START_REF] Méon | Normapolles. Comparaison entre l'Europe centrale et du Sud-Est pendant le Cénomanien et le Turonien : évolution de la biodiversité et paléoenvironnement[END_REF] and several species were usually encountered from other mid to late Cenomanian assemblages from western France [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF][START_REF] Néraudeau | Upper Cretaceous amber from Vendée, north-western France: Age dating and geological, chemical, and palaeontological characteristics[END_REF]. If they were to be found in Neau lignites, they are certainly very scarce.

The palynoflora from Neau is then probably younger than the charentese palynofloras, and older than Normapolles-rich mid Cenomanian palynofloras from Vendée (western France; [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF][START_REF] Néraudeau | Upper Cretaceous amber from Vendée, north-western France: Age dating and geological, chemical, and palaeontological characteristics[END_REF], agreeing with the regional stratigraphic correlations of [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF]. A possible age of upper lower Cenomanian or lower mid Cenomanian (which is virtually the same) is then attributed to the Neau amber-bearing lignitic clays.

Palaeoenvironment

Such poorly diversified conifer-dominated plant assemblage is common in the Laurasian littoral floras during the Albian-Cenomanian. Albian-Cenomanian floras yielding the conifer Frenelopsis as well as the ginkgophyte Eretmophyllum (or Nehvizdya) were reported from several palaeobotanical sites of western France, including the Archingeay quarry and the Renardières quarry in Charente-Maritime [START_REF] Néraudeau | Stratigraphie et paléontologie (plantes, vertébrés) de la série margino-littorale Albien terminal À Cénomanien basal de Tonnay-Charente (Charente-Maritime, France)[END_REF], and the Brouillard quarry in Maine-et-Loire [START_REF] Pons | Les organes reproducteurs de Frenelopsis alata (K. Feistm) Knobloch, Cheirolepidiaceae du Cénomanien de l'Anjou, France[END_REF][START_REF] Néraudeau | L'ambre cénomanien d'Anjou: stratigraphie et paléontologie des carrières du Brouillard et de Hucheloup (Ecouflant, Maine-et-Loire)[END_REF]. The abundance of both the leafy axis Frenelopsis and the dispersed pollen grain Classopollis as well as the chemical signature of the amber suggest that Cheirolepidiaceae were one of the main component of the flora bordering the palaeokarsts from Neau. Although both are isolated in the sediment from Neau, Classopollis was reported attached on microsporangiate cones of Frenelopsis alata from other Cenomanian palaeobotanical sites of Europe (e.g. [START_REF] Kvaček | Frenelopsis alata and its microsporangiate and ovuliferous reproductive structures from the Cenomanian of Bohemia (Czech Republic, Central Europe)[END_REF]. As it was remonstrated in the Albian-Cenomanian deposits of western France (e.g. [START_REF] Pons | Les organes reproducteurs de Frenelopsis alata (K. Feistm) Knobloch, Cheirolepidiaceae du Cénomanien de l'Anjou, France[END_REF][START_REF] Néraudeau | Stratigraphie et paléontologie (plantes, vertébrés) de la série margino-littorale Albien terminal À Cénomanien basal de Tonnay-Charente (Charente-Maritime, France)[END_REF][START_REF] Néraudeau | L'ambre cénomanien d'Anjou: stratigraphie et paléontologie des carrières du Brouillard et de Hucheloup (Ecouflant, Maine-et-Loire)[END_REF]Girard et al., 2013aGirard et al., , 2013b;;[START_REF] Moreau | Plant inclusions from the Cenomanian flints of Archingeay-Les Nouillers, western France[END_REF][START_REF] Moreau | Albian flora from Archingeay-Les Nouillers (Charente-Maritime): comparison and synthesis of Cretaceous meso-and macro-remains from the Aquitaine Basin (southwestern France)[END_REF] and other European localities (e.g. [START_REF] Kvaček | Frenelopsis alata and its microsporangiate and ovuliferous reproductive structures from the Cenomanian of Bohemia (Czech Republic, Central Europe)[END_REF], the genus Frenelopsis is related to littoral environments commonly with strong marine influence. Ecophysiologically, the xerophytic characters of the conifer Frenelopsis clearly show that the flora from Neau was adapted to withstand intense sunlight and coastal environments exposed to desiccant conditions coupled in haline settings: sheathing leaves, thick cuticle, grooved epidermal cells, epidermal hairs, stomata in sunken lines, and stomata with two levels of papillae [START_REF] Thévenard | Xeromorphic adaptations of some Mesozoic gymnosperms. A review with paleoclimatological implications[END_REF]. These morphoanatomical characteristics allow a reduction of solar radiations, drying air circulations and evapotranspiration.

Classopollis shows a wide geographical distribution. The genus has been reported in high proportions from near-coastal settings, such as sandy bars or coastal islands with welldrained soils [START_REF] Alvin | Cheirolepidiaceae: biology, structure and paleoecology[END_REF][START_REF] Abbink | Palynological investigations in the Jurassic of the North Sea region[END_REF], as well as in upland slope habitats [START_REF] Filatoff | Jurassic palynology of the Perth Basin, Western Australia[END_REF][START_REF] Vakhrameev | The Middle-Late Jurassic boundary, an important threshold in the development of climate and vegetation of the Northern Hemisphere[END_REF]. However, the abundance of Classopollis in the Jurassic and Cretaceous of Russia and North America shows a marked decrease northward, at higher and cooler palaeolatitudes [START_REF] Pocock | Palynology of the Jurassic sediments of Western Canada. Part 2. Marine species[END_REF]. When recovered with Frenelopsis remains, the presence of this genus is likely to be indicative of warm coastal habitats. The observation of numerous Classopollis clusters within the amber from Neau suggests that their parent plants grew in the vicinity of the depositional environment. The presence of very scarce Surculosphaeridium longifurcatum and foraminifera lining supports the hypothesis of an environment submitted to occasional marine inputs (Appendix S1; Fig. 6A).

The composition of the palynological assemblages of Neau is very similar to that of the Cenomanian assemblages from western France described by [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF] and [START_REF] Polette | Palynological assemblage from the lower Cenomanian plant-bearing Lagerstätte of Jaunay-Clan Ormeau-Saint-Denis (Vienne, western France): stratigraphic and paleoenvironmental implications[END_REF], sharing numerous common species. The present study underlines the fact that all lower to mid-Cenomanian spore assemblages from western France are dominated by Anemiaceae, Gleicheniaceae, and Cyatheales, with often numerous lycopods, mostly belonging to Camarozonosporites (see [START_REF] Azema | Des miospores du Cénomanien moyen[END_REF][START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF][START_REF] Polette | Palynological assemblage from the lower Cenomanian plant-bearing Lagerstätte of Jaunay-Clan Ormeau-Saint-Denis (Vienne, western France): stratigraphic and paleoenvironmental implications[END_REF]. Modern Cyatheales are concentrated at the tropics but can occupy varied habitats [START_REF] Kramer | The families and genera of vascular plants. I. Pteridophytes and Gymnosperms[END_REF]. Their recurring presence at Neau agrees with a globally warm mid-Cretaceous climate, already suggested by the numerous Classopollis pollen grains [START_REF] Kujau | Reconstructing Valanginian (Early Cretaceous) midlatitude vegetation and climate dynamics based on spore-pollen assemblages[END_REF]. Representatives of the Gleicheniaceae are considered to be opportunistic, pioneering tropical to subtropical plants, adapted to long droughts, growing in unstable habitats such as dry forests and wetlands that occasionally dry out [START_REF] Coiffard | Early Cretaceous angiosperm invasion of Western Europe and major environmental changes[END_REF][START_REF] Mehltreter | Fern ecology[END_REF][START_REF] Kujau | Reconstructing Valanginian (Early Cretaceous) midlatitude vegetation and climate dynamics based on spore-pollen assemblages[END_REF]. Modern Anemiaceae usually develop under warm and humid environments, and their Mesozoic relatives may have grown along riverbanks, or as understorey in forests [START_REF] Dettmann | Spore morphology of Anemia, Mohria, and Ceratopteris (Filicales)[END_REF][START_REF] Van Konijnenburg-Van Cittert | Ecology of some Late Triassic to Early Cretaceous ferns in Eurasia[END_REF]. However, some species of Anemiaceae are adapted to more arid conditions, and may tolerate partial desiccation [START_REF] Proctor | Poikilohydry and homoihydry: antithesis or spectrum of possibilities?[END_REF][START_REF] Schrank | Pollen and spores from the Tendagru Beds, Upper Jurassic and Lower Cretaceous of southeast Tanzania: palynostratigraphical and paleoecological implications[END_REF]. No suggestion has been previously made about the ecological requirements of the potential parent plant of Camarozonosporites, which has been associated with Lycopodiaceae [START_REF] Ravn | Miospores from the muddy sandstone (upper Albian), wind river basin, Wyoming, USA[END_REF][START_REF] Schrank | Pollen and spores from the Tendagru Beds, Upper Jurassic and Lower Cretaceous of southeast Tanzania: palynostratigraphical and paleoecological implications[END_REF]. Extant forms usually develop in fairly sheltered, dark and humid environments, such as conifer forests understorey. They also can grow along riverbanks and streams, or as epiphytes on mossy tree trunks [START_REF] Rusea | Ecology and distribution of Lycopodiaceae Mirbel in Malaysia[END_REF]. A few species, such as Lycopodiella cernua, are even adapted to more arid condition, and can develop in open and sunny areas [START_REF] Rusea | Ecology and distribution of Lycopodiaceae Mirbel in Malaysia[END_REF]. While some representatives of Gleicheniaceae, Anemiaceae, and Lycopodiaceae correspond to drought-resistant plants, the majority of extant ferns flourishes in wet conditions, and a high spore content is generally used as indicator of humid settings. Subordinate elements of the palynoflora, such as Todisporites, or diversified Eudicots pollen assemblage support the hypothesis of the existence of a partly riparian hygrophilous plant community [START_REF] Abbink | A sporomorph ecogroup model for the Northwest European Jurassic-Lower Cretaceous: concept and framework[END_REF][START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF]. Other minor forms recovered from Neau palynoflora, such as Densoisporites and Alisporites, have been interpreted as indicators of tidaly influenced environments [START_REF] Abbink | A sporomorph ecogroup model for the Northwest European Jurassic-Lower Cretaceous: concept and framework[END_REF]. The recurring presence of several species of cupressaceous inaperturate pollen grains herein, including Inaperturopollenites dubius, Taxodiaceaepollenites hiatus, Perinopollenites halonatus, along with araucariaceous related forms (Appendix S1) could also suggest also the existence of conifer forests linked to wet lowlands, such as in low salinity back-swamp environments, based on the ecological requirement of some modern Cupressaceae [START_REF] Schrank | Pollen and spores from the Tendagru Beds, Upper Jurassic and Lower Cretaceous of southeast Tanzania: palynostratigraphical and paleoecological implications[END_REF][START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF]Appendix S1). [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF] and [START_REF] Polette | Palynological assemblage from the lower Cenomanian plant-bearing Lagerstätte of Jaunay-Clan Ormeau-Saint-Denis (Vienne, western France): stratigraphic and paleoenvironmental implications[END_REF] discussed extensively the hypothetical environmental settings corresponding to Cenomanian palynofloras from western France, and described various riparian to coastal plant communities which developed under humid and warm condition. They are associated with palynological assemblages grading from (1) assemblages clearly dominated by Classopollis which would indicate downstream and coastal environments associated with xeric communities (cheirolepids, some representatives of drought-tolerant Gleicheniaceae and Anemiaceae) to (2) assemblages dominated by diversified spores, bisaccates and angiosperm pollen grains which would represent more upstream depositional environments associated with riparian hygrophilous plant communities. The composition of the palaeobotanical and palynological assemblages from Neau is intermediate. The corresponding depositional environment was subjected to a very limited connection to the sea, while associated with both drought-resistant plants and hygrophilous ferns and angiosperms. It could well have corresponded to the upstream portion of a mangrove or the most inner part of a lagoon. Depositional settings associated with mangrovetype environments has now been abundantly suggested to accommodate lower to mid-Cenomanian plant communities of western Europe [START_REF] Batten | Wealden palaeoecology from the distribution of plant fossils[END_REF][START_REF] Gomez | Diversity and histology of a plant litter bed from the Cenomanian of Archingeay-Les Nouillers (southwestern France)[END_REF][START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF][START_REF] Polette | Palynological assemblage from the lower Cenomanian plant-bearing Lagerstätte of Jaunay-Clan Ormeau-Saint-Denis (Vienne, western France): stratigraphic and paleoenvironmental implications[END_REF]. The abrupt increase of the abundance of angiosperm pollen grains is interpreted as a reflection of the group's radiation.

Fig. 1 .

 1 Fig. 1. Simplified geological map of the Neau area, in the Mayenne department, with location of the studied quarry.

Fig. 2 .

 2 Fig. 2. Geological sections of the Cenomanian karsts from the Neau quarry. A. Synthetic section of the karsts with lignite and amber, observed by the authors (Cmb = Cambrian limestones; CnL = Cenomanian lignites; CnS = Cenomanian sand; CnG = Cenomanian Glauconitic facies). B. Geological section published by Azema et al. (1972), with location of their palynological samples S1 to S12.

Fig. 3 .

 3 Fig. 3. Lignite and amber deposits from the Neau quarry. A. General view showing the Cenomanian lignites (CnL) in karsts incising the Cambrian limestones (Cmb); at the top of the quarry, Cenomanian glauconitic sands overlap both Cenomanian white sands (CnS) and Cambrian limestones. B. One Cenomanian karst showing at its top the contact between the lignites containing amber (CnL) and the glauconitic sands (CnG); the bag of the collector contains a large piece of fossil wood. C. Lateral view of a Cenomanian karst with the lignites (CnL) directly in erosive contact with the Cambrian limestones (Cmb) (photographs D. Néraudeau).

3

  Plant remains from the lignitic clay 3.1 Coalified compressions and cuticles from the lignitic clay Conifers Family Cheirolepidiaceae Genus Frenelopsis Schenk, 1869 emend. J. Watson,1976 Frenelopsis sp. (Fig. 4B-E) Material. Forty-three specimens, from which IGR-PAL-2830 to IGR-PAL-2833 are figured.

Fig. 4 .

 4 Fig. 4. A. Amber, cuticle and wood remains extracted after soaking of sediment in a solution of hydrogen peroxide. B-E. Leafy axes of the conifer Frenelopsis sp. showing the characteristic tree short parts of the leaves (located by arrows), IGR-PAL-2830 to IGR-PAL-2833. F. Conifer cone scale IGR-PAL-2834. G-H. Fragments of leaves ascribed to Eretmophyllum obtusum showing the characteristic bifid veins (located by arrows), IGR-PAL-2835 and IGR-PAL-2836. Scale bars: A = 1 cm; B-D and G-H = 5 mm; E = 1 mm; F = 2 mm.

(

  Fig. 4G-H and Fig. 5A-J) Material. Sixteen specimens, from which IGR-PAL-2835 and IGR-PAL-2836 are figured.

Fig. 5 .

 5 Fig. 5. Eretmophyllum obtusum. A-B. Details of cuticle showing the arrangement of cells, and the random orientation of stomatal apparatuses (white arrows), IGR-PAL-2844. C-F. Sketches of stomatal apparatuses showing arrangement of subsidiary cells. G. Arrangement of resin bodies (white arrows) preserved in the mesophyll between veins IGR-PAL-2845. H-J. Rounded and spindle-shaped resin bodies. Scale bars: A and H-J = 500 mm; B = 200 mm; C-F = 100 mm; G = 2 mm.

Fig. 6 .

 6 Fig. 6. A. Abundance charts of the most productive palynological assemblages from the amber-rich lignitic clays of Neau. Charts are based on the botanical affinities of the various spores and pollen morphotypes. Encountered genera: 1: Aequitriradites, Stereisporites, Triporoletes; 2: Camarozonosporites, Densoisporites, Retitriletes; 3: Gleicheniidites, Ornamentifera; 4: Cyathidites, Deltoidospora, Dictyophyllidites, Matonisporites, Toroisporis; 5: Appendicisporites, Cicatricosisporites, Distaltriangulisporites; 6: Auritulinasporites, Baculatisporites, Concavissimisporites, Laevigatosporites, Microreticulatisporites, Patellasporites, Todisporites; 7: Parvisaccites, Piceaepollenites, Podocarpidites, Pristinuspollenites; 8: Araucariacites, Balmeiopsis, Callialasporites; 9: Classopollis; 10: Exesipollenites, Inaperturopollenites, Perinopollenites, Taxodiaceaepollenites; 11: Alisporites, Afropollis, Cycadopites, Eucommiidites, Monosulcites; 12: Clavatipollenites, Dichastopollenites, Pennipollis, Retimonocolpites, Stellatopollis, Transitoripollis; 13: Artiopollis, Nyssapollenites, Phimopollenites, Retitrescolpites, Tricolpites. Species list, counts and references are available on Appendix S1. B-Z. Dinocysts, spores and pollen grains recovered from Neau lignitic clays. Accompanying data are palynological preparation and England Finder coordinates. Scale bars represent 10 mm. B. Surculosphaeridium longifurcatum (Firtion) Davey et al., S3-Cd9, N30.4. C. Triporoletes cenomanianus (Agasie) Srivastava, S11-Cd28, R45.4. D. Camarozonosporites insignis Norris, S4-Cd16, J31.4. E. Cicatricosisporites cf. mohrioides Delcourt and Sprumont, S11-Cd31, P36.0. F. Cicatricosisporites annulatus Archangelsky and Gamerro, S3-Cd9, F29.2. G, H. Appendicisporites bilateralis Singh, S3-Cd7, K41.0. I, J. Appendicisporites insignis (Markova) Chlonova, S4-Cd11, J46.1. K. Baculatisporites sp., S3-Cd8, R48.1. L. Patellasporites tavaredensis Groot and Groot, S11-Cd28, J42.0. M. Podocarpidites biformis Rouse, S3-Cd6, M32.3. N. Araucariacites australis Cookson ex Cooper, S11-Cd31, L47.1. O. Eucommiidites minor Groot and Penny, S11-Cd29, P45.0. P. Transitoripollis anulisulcatus Góczán and Juhász, S3-Cd6, M31.0. Q. Dichastopollenites reticulatus May, S4-Cd14, S46.4. R. Dichastopollenites sp. 4 sensu Heimhofer et al., (2007), S11-Cd29, B40.0. S. Stellatopollis cf. largissimus Singh, S4-Cd16, K48.0. T. Artiopollis indivisus Agasie, S4-Cd16, K52.1. U. Nyssapollenites albertensis Singh, S3-Cd8, R48.3. V. Tricolpites cf. vulgaris (Pierce) Srivastava, S3-Cd7, H48.4. W. Tricolpites aff. virgeus (Groot, Penny and Groot) Hasenboehler, S11-Cd28, F35.0. X. Phimopollenites tectatus Singh, S3-Cd7, K47.1. Y. Phimopollenites megistus Singh, S4-Cd16, M33.1. Z. Phimopollenites cf. pannosus (Dettmann and Playford) Dettmann, S11-Cd33, L37.4.

Fig. 7 .

 7 Fig. 7. Large amber pieces from the Neau quarry. A. Milky brown variety. B. Translucent honey variety. C. Cork colour variety. D. Empty piece of cork colour variety; note the black colouring of the peripheral part, linked to the proliferation of the sheated bacteria Leptotrichites resinatus. Scale bar = 10 mm.

Fig. 8 .

 8 Fig. 8. Amber features. A. Forms and aspects of the collected amber grains, some having kept the characteristics of the original resin drops; note the abundance of opaque grains with earthy colours. B-E. Sections of grains in thin sections showing various situations of more or less opaque grains. F. Cracked external surface of a grain under SEM. G. Stack of resin flows within a grain. H. Opaque grains marked by dense filamentous networks. I. Opaque grain containing many bubbles and colonization by filamentous networks.

Fig. 10 .

 10 Fig. 10. Palynomorphs inclusions in amber. A-F. Inclusions of Classopollis pollen grains in the Cenomanian amber of Neau (Mayenne). Generally pollen grains are grouped in vacuoles of the amber and can be numerous (A, B, E, F), IGR-PAL-2837 to IGR-PAL-2840. Only a few ones are isolated in the fossil resin (C, D), IGR-PAL-2841 and IGR-PAL-2842. Note the dense filamentous network due to the colonization of the resin by a sheathed bacterium (sb). A-D. Optical microscope. E-F. Confocal microscope (CLSM).

Fig. 9 .

 9 Fig. 9. Optical (A-B) and SEM (C-F) photographs of wood fragments. A. Large piece of fossil wood showing large Teredo borings on the left and numerous tiny borings (insect attacks?) on the right, IGR-PAL-2828. B. Piece of branch showing tiny borings IGR-PAL-2829. C. Areolated pit inner casts; note that tori left a circular depression in the centre of the casts (magnification  1700). D. Araucarian row of uniseriate contiguous radial pits (magnification  1300). E. Five araucarioid cross-fields, with poorly preserved contiguous alternate cupressoid oculipores (magnification  1600). F. An isolated areolated pit (foreground) and an araucarioid cross-field (background) (magnification  3500). SEM observations have been made on specimen IGR-PAL-2846. Scale bar for A and B: 10 mm.

Fig. 11 .

 11 Fig. 11. Total ion chromatogram from the THM-GC-MS analysis of Neau amber form A (A) and form B (B). Numbered peaks refer to identified compounds inTable 1 and Appendix S2.

Table 1 .

 1 (continued).

	No.	Compound name	m/z identification	m/z int	MSF	Form A	Form B
	34	Naphthalene-1,2,3,4,4a,7,8,8a-octahydro-1-	109, 121, 189, 236	121	18	0.5	n.d.
		methoxymethyl-1,4a,5,6-tetramethyl methyl
		ester (VId)
	35	Tetramethylnaphthalene isomer	169, 184	169	5	0.1	0.5
	36	Naphthalene

  characterized by centripetal colonization of filamentous networks. They are essentially sheathed bacteria identifiable as Leptotrichites resinatus Schmidt 2005 whose colonization density in the

Table 2 .

 2 Relative proportions of the three categories of identified compounds and of labdanoid diterpenes. Compositional ratio calculated on the distribution of labdanoid diterpenes.

		Form A	Form B
	Relative proportions of identified compounds
	Labdanoid diterpenes	64	20
	Methyl(hydro)naphthalene	21	64
	and methylphenanthrene a
	Tricyclic diterpenes	15	16
	Relative proportions of labdanoid diterpenes
	Carboxylic acid	66	11
	Alcohol	8	1 5
	1-Dimethyl	3	1 2
	1-Methyl	23	62
	Compositional ratios SC14/ SC15
	Carboxylic acid	0.23	0.11
	Alcohol	0.22	0.09
	1-Dimethyl	0.77	0.34
	1-Methyl	0.71	0.88
	All labdanoid diterpenes	0.24	0.17

a Including amberene.

D.Néraudeau et al.: BSGF 2020, 191, 39

Acknowledgements. The authors are greatly indebted to the Society Chaux & Dolomie Françaises/Lhoist France Ouest for the authorization to access to the outcrop. They thank Paul Bessin and Valentin Prugneaux for their participation to the field trip. The preparation of thin sections was performed by Severin Morel (UMR 7207). We thank also Géraldine Toutirais (PTME, Muséum National d'Histoire Naturelle, Paris) for his assistance with scanning electron microscopy. The CLSM investigations were performed at the Institute of Biology Paris-Seine Imaging Facility that is strongly supported by the "Conseil Regional Île-de France", the French National Research Council (CNRS) and Sorbonne University.

Supplementary Material

Appendix S1. Species list of palynomorphs recovered from the productive lower mid-Cenomanian clay deposits of Neau, along with potential botanical affinities and counts per sample. Appendix S2. Molecules identified in the pyrolysates of Neau ambers. Individual compounds are labelled according to the identification of peaks in Table 1.

The Supplementary Material is available at https://www.bsgf. fr//10.1051/bsgf/2020039/olm.


Julie Séguéla

Gilbert Saporta

Automatic Categorization of Job Postings

Conclusions & Future Work

• Our methodology allows to :

-Standardize the job category on all our posting database -Automate job posting labeling according to each job board referencing system

• Future work :

-Use the job category to recommend the use of job search web sites in order to optimize recruitment performance

Automatic Categorization of Job Postings

Julie Séguéla 1,2 and Gilbert Saporta 1 1 Laboratoire Cédric, Conservatoire National des Arts et Métiers, Paris, France 2 Multiposting.fr, 33 rue Réaumur, Paris, France, jseguela@multiposting.fr

Context & Objectives

• Context :

-Recruiters need to assess job posting performance on job search web sites -But all sites have different ways to reference job postings

• Objectives :

-Be able to identify the job occupation whatever the posting -Improve the categorization efficiency thanks to a processing adapted to the particularity of job postings

Method : Posting Representation & Classification

Comparison of method average precisions (without and with implementation of a misclassification error cost)

Results

Corpus

• French corpus of 700 job postings (baseline method : 1060 terms)